E1681-4: Ham Radio General Class FT8, WSPR, Beverage Antennas & More

all forms of digital modes. Digital modes are restricted to CW SLASH data segments and the HF bands. They're found near the top of the CW segment on twenty meters. Most PSK stations are near fourteen seventy r TTY, other modes between seventy and fourteen. Table coming up to show some of that. CW isn't formally restricted anywhere in the bands. It's a digital mode, but you can use it anywhere. They has special privileges. Data rates and bandwidths are specified

by the FCC rules. Digital codes not specified by the FCC must be public. You can have an experimental mode, but it's got to be published. People have to know what it is. Radio teletype originally used mechanical teleprinters, but migrated as computer sound cards. Most people use a computer sound card to generate their digital tones in these days. PSK thirty one Real, Real Popular, it's a good Week.

Signal mode uses load transmit, packet teletype over radio win more is Windows based messaging over radio win war All those are popular types of HF digital modes. And there's packet radio common on VHF U HF twelve and nine six hundred bought on those bands. Okay, so here's the bands, here's the frequency range or where you will find some of the digital stuff hanging out. Most people here to that's pretty people follow it pretty well. So here's some

definitions you might want to know for digital stuff. Airlink that's the part of the comp system that involves radio transmission and reception of signals. I don't think I've ever used that much, but air that's an airlink. Bit is the fundamental unit of data, as zero or a one, representing all the part of a binary number. There's the bit rate. That's the number of digital bits per second

sent from one system to another. Bod is a number of symbols per second, and Symbols can be ten bit or eight bit based on the protocol you're using, but it's symbols per second sent from one station to another. The duty cycle is the ratio of the time that the transmitter is on to the total time plus the off time. Protocol are the rules that control the method used to exchange data between systems, and the mode is the combination of a protocol with the modulation method. Digital

modes are regulated as voice emissions by the FCC. Digital Voice modes and those include d STAR System, fusion AR Digital Voice System d DMR. FSK individual bits of data encoded as tones. FSK uses tones as data are transmitted. Different tone frequencies are used to represent the one or the zero. The frequencies in a two tone FSK system called mark in space, space represents a zero and mark

represents a one. In direct FSK, the frequency of the transmitter's BFO is controlled by a digital data signal from the computer, So either can send two tones through the audio passband or you can actually change the carrier frequency the same thing. It's a frequency shift. It's the same result audio frequency shift K, which is probably ninety eight percent of what we do in the hand radio is use audio tones modulated on single sideband or FTEM through

the microphone input generated by a sound card. Typically, multiple FSK uses more than two tones and are used to create more codes. Most common type of the fs the PSK the face shift king. Most common type of face shift is to invert one of the tone waveforms by shifting at one hundred and eighty degrees. Rapid changers and face can be heard from from the human ear as

a rasp, noise or buzz. The signature of a PSK sitting on the air received by by CW or CW single sideband receivers sort of sound like an old computer mode. Let's let's talk about some questions here in what segment of the twenty meter band are most digital modes operations commonly found. It's around between fourteen seventy and four D. What is a direct binary FSK modulated signal direct? Now we're doing direct, so you want to key the oscillator

directly with their digital signal? Must be v okay. How are the two separate frequencies of a frequency shift key signal identified? Usually do marking space? Which of the following provided digit number of digital voice modes Okay, remember digital voice modes DMR D Star infusion. Those are digital voice modes. All these other ones have non voice modes. Okay, talk

about some character based modes. Simplest use of digital communications as mode in which individual characters entered by an operator and transmitted to another station and they appear on another by another read by another operator, such as Morse code. Uh. Speeds are low but convenient to use and require a little additional equipment than a sound card or modem. So

a lot of times it's a keyboard to keyboard. I typed the letter A, I transmitted it, and receive station gets it puts on his computer A. So we just did some character based transmission, sometimes referred to as keyboard to keyboard or chat. You transmit a stream of characters without additional data. That's referred to as unstructured. Oldest form of hand radio digital communication is r tt Yuh. This you sends the This is called BOTTO. It's a timing

sequence for the bit pattern. Uh. Here we're trying to send the letter DS and dog. It starts a bit is set. You have some bits that tell it when it's starting. Then the data comes across and then you get a stop bit and you're done, and how fast it goes out is a bawd raad okay. R t t Y uses the BODO code, which is which represents each character has a five bit sequence. Five bit allows for thirty two different characters. That's not enough for their

attire English language, you know, numerals and punctuation. There's two special flags, letters and figs that are used to switch between the two characters sets, and that doubles the amount of characters that can be sent. So there's a special character as a guy sending letters or numbers or something. You can set it and you get you know, you don't increase your your your five bits don't have to

get bigger. Difference between mark and space tones is called the signal shift rtt Y. Usually that's at one hundred and seventy hertz. It's most common. It's not a rule, but that's what just better Buy uses. PSK thirty one is another mode. It's probably the most popular face shift key mode. It's called thirty one BOD by some people US as a sound card to generate the the rtt

Y signals. Thirty one is the symbol rates Actually thirty one point twenty five bod designed for keyboard to keyboard communication typing at rates up the fifty words per minute. So that's fast enough for me because I couldn't type that fast and as referred to as BPSK thirty one QPSK since two audio tones, so there are now four possible phase combinations. Okay, so since PSK has two tones, you have to select the right sideband to the correct

sideband here, either upper or lower. If you're in the wrong sideband, you're gonna you're gonna invert your tone, so you're not gonna decode it. So make sure you understand what band you're on. Usually it's upper sideband even no matter what band you're on for the for the digital modes, but if you're tuned in and you're not copying, swap sidebands and see if it starts reading correctly, so it

is sideband sensitive. PSK uses a variable link character called very COODE that assigns shorter codes to common characters and longer codes for uncommon characters like Morse code, capital letters, and punctuation take longer decent if you're using If you're used to do RTTY with no lowercase, turn off caps

lock because they take more. Something I didn't know for a while was I didn't know it was any different on you know, the character you sent, whether it's sent eight characters or three, was based on what you had tied. Good news. Really, I couldn't die types so slow. It didn't make any difference. But that's interesting fact there. So QPSK thirty one and PSK thirty one have about the same band with two point five killer hertz. QPSK is

sideband sensitive and it's encoding provides error detection. So what's the most common frequency shift E mission on the amateur HF bands on the shift one hundred and seventy hertz number B letter B? Which of the following is characteristic of QPSK coding error corrections approximately the same? Sideband sensitive? I think all those sound right, that's correct. Which of the following describes a BOTTO code? It's a five big

code at BC. Which of the following statements is true about PSK thirty one upp acase on use very coode b B with b B. Which type of code is used for sending characters in a PSK thirty one signal very code A? All right, talk about some packet based. These are structured modes and they're derived from early teletype over radio or computer to computer network systems. Hams have adapted the protocols creating packet radio, pack tool, win More

and other communication systems. Some packet modes JT sixty five and FT eight require precisely defined transmission periods. The utility software is a able to keep your computer synchronized within one second of the standard time. So some of these modes like FT eight get you sixty five your your local time source is important to have it sync within a second of the guy you're talking to. So some of the basis of packet packet refers to the transmission

of data and structured groups called frames. Packet communication systems package data with the package the data with control and routing information, and add error detection information. Each package or of header, data and trailers called the frame. Different packet protocols are used for different sets of information and mesags of creating the frame, but basically the same. You use to have a header the data, and you have some

kind of trailers. The header contains the bit patterns that allow receivers to sync with the package structure, control of routing information in some then for some protocols, air detection correction data is the data is the data to exchange between the systems, usually asking characters, usually compressed for efficiency. The trailer vent is added on the information at the end for error detection. Forward error correction goes beyond simply

detecting errors. By including redundant encoded info with the data, it's possible for receiver to correct certain types of data errors. Most common air detection mechanism is called a cyclic redundancy check or CRC. On an ARQ system, automatic repeat requests. If mismatched is detected, the receiving system responds with the knack, which not acknowledged and the proto the protocol request retransmission

transmitting will continue to send. The transmitting system will continue to send pack it until it's received without air or retransmissions has reached a limit okay. ARQ is used in packtor, packet radio, and win more. ARQ protocols were used for wired network connections and the transmission can only be received from one receiving station during the connection. This means you can't break into a contact between two stations using ARQ. So if Jason and I are talking ARQ. Our systems

are trying to talk to each other. If somebody else gets in there, we're not going to respond to them because we're trying to complete our handshakes. So that's what they're talking about here. You can't break If two stations are talking, don't try to break into them because you're not going to be acknowledged and you're just going to

cause interference on what they're trying to do. So that a station can advertise as presence, however, ARQ protocols provide a broadcast mode to trans meant without another station having to established consonants UH contact, So so you can there's a there's a there's a mode where you just like calling c Q and a ar Q and if somebody here's it, their station will respond on the two view will pair up. I used to do this long time ago amp uh app's the app core UH long am

I forgot what it's called long time ago. A mod mode is also provided so that stations can listen to the other stations without getting into their error correction scheme right. Using the moond mode allows you to determine if the frequency is occupied by two stations having an a ar Q mode contact. It's designed to transfer data between only two stations, mean that you can't break into the contact.

Talked about that packet radio t R system developed to compensate for transmission errors and r t t Y used almost exclusively on the UHF bands, packet radios and shorts bursts of characters with error detection and correction data. It's based on computer network protocols x DOT two five, one of the oldest packet switching communications protocols popular during the late nineteen seventies and eighties. Back when I was learning

about stuff that was that was slick stuff. Back in the day, packets exchange using VHF FM voice at twelve hundred and ninety six hundred BOB. Today we've got we've got some improvements over that. It does not work well with HF broadcasts because of the noise and fading and AHF you to have to be at three hundred bar or lower. HF UHF packets still big around here, works works good day. Pactor and win More so these reliably, I mean the rival they're kind of low, but they're

reliable and they're robust. Packed tour is packet based to you are win More's win based to you are they work pretty well. Packed Tour one uses frequency shift King modulation. Packed Tour one through four use advanced PSK pack to four not yet legal for us amateurs, might be coming close. I mean there's there's legislation they're working on getting that, but it's a very good mode. They work fine. Pack Tor and Varro modes have overcome some of the issues

with HF. I know, we use Vara on our packet system here. We do dual mode packet or the regular packet twelve twelve hundred bod. Varro works well and seems to be doing good round here. Okay. Win Link so win Link is a is a way to transfer email and messaging over HF. We use it VHF UHF here also for our areas work and it's a well established group. We've got several wind Link ports here in town and they work very well. And wind Link isn't a mode,

it's a gateway communications system. It uses the Internet to connect it's email services with a gateway and mailbox stations around the world on HF. VHF and UHF said it's been around the wild, it's been improved a lot, and it's fairly reliable and all those fails. It's a good mode to get stuff going. Win Link stations did not connect directly to the Internet, but they provide a means for stations out of your local Internet coverage to connect

in range. So that's pretty cool. If you have a regional outage somewhere, power data, fiber, oppet cables cut, no Internet allows you to connect RF to someone plays else that does have Internet connection. You can get your email and your data truth so even without Internet connectivity. Win Link Express, which is a program you can download, runs in a PC, can act as a standalone mailbox station or communicate directly with each other. You can do peer

to peer connections. Done all that so on HF. Win Link uses pack Tour and Vara modes. Uh Var is the most popular, is the more popular. Vara is a tour software developed by e A five HBK software, So check that out. Okay, FT eight and whisper. These are called Wheat signal modes. They're supported by the WSJT software suite. A lot of cool modes in there. Here's a you can go check it out that They use eight tone, frequency shift, king modulation and air decoding. Correction to enable

successful decoding. Very low signal to noise ratios. FT eight's and seventy five bit messages limits messages to call signs, good locations and signal reports only. FT eight signal reports are on the signal deloise ratio, so a report of plus three means the signal was three dB above the noise floor. We's com in FT eight. Transmission ranges are in fourteen seven four to fourteen seven seven. Be sure to locate a clear frequency and selected timeslot that doesn't

interfere with the calling stations. Specifically when responding the clear frequency and the ultimate time slot so that used by the calling station. So FD eight's very popular. Done a lot of that that myself. It's a lot of fun Whisper. It's an HF propagation passed the week signal things. I run two Whisper notes from my home on thirty and twenty meters all the time. It doesn't support two way QSOs, but I have a beacon that transmits and all the time, and I can go look at signal reports and see

who's seen my signal around the country. Spun built the Whisper nodes myself. Fairly easy to do, and it's fun to play with. Okay, low power Whisper transmitters generate coded packets. Stations that receive these reports can report them on the whispernet dot org and it's fun to go look at your signal reports and see what you can see. So okay,

amateur wireless networks certain wireless networks. When networking frequencies overlap with amateur bands, amateurs are able to use them for many of the same purposes that under license users are able to, such as text messages, voice over IP, email, et cetera. If you operate a wireless network on FCC Part ninety seven frequencies, you must comply with the prohibit

the prohibitions on encryption. HAM used two basic network topologies, Mesh and Star configurations, and advantage of the met network prot topology is that if one node fails, the packet may be able to find this destination by routing through another available node. So here's some wireless network frequencies that that we have that we can share and use. And in these bands, there are some HAM specific channels that are on our side, which really makes it nice. Arden

is an amateur radio emergency data network. It's a mesh network can be made uses commercially available routers and the nine hundred two point four two point four five point eight giggers band Arden website one of the best websites I've seen for information and how to understand and get information. They do a great job. There's a go to the ardmesh dot org if you're inntioned in. That generally used during the emergency to support communication events like road races,

parades and other large gatmies. But it uses that you can use the commercial items h put them into the handbands and they work. They weren't great, Let's see. It's a digital protocol users one link B. Which of the following is a good practice when using a transmittered frequency to answer a station calling CQ using FT eight UH,

I think you want to call. You want to find a clear frequency during the same time slot as the calling UH and the ultimate timeslot as the calling stations that would be D. Which of the following is required when using FT eight You need a computer with accurate time within a one second. That's the key. B. How do you join a contact between two stations using the pack tool protocol UH? It is not possible see because uh, it's only limited to two stations, so see is it.

What is the primary purpose of an amateur AIO data network mesh network. Let's c to provide high speed data services during emergency or a community event. Which of the following describes win Link. It's a wireless network capable of both VHF and HF band operation, form of packet radio and all those D. What is another name for a win link remote message server. It's called the gateway. Which of the following is a common location for FT eight.

It's between fourteen oh seventy four and fourteen oh seventy seven C. What type of modulation is used by FT eight? It uses eight tone frequency shift key. Hey, what is QPSK modulation? It's modulation using let's see the angles, degrees, face shifts at the bottom. D. Which digital mode is used as a low power beacon for assessing HF propagation be a whisper node weak signal propagation. What part of packet radio frame contains the routing and handling information? That's

the preamble. Excuse me, sorry, it's the header. The header has the UH. The information contained a routing handling information? Sorry about that? The header in an an ARQ mode. What is meant by NAC response to a transmitted packet? It means how does forward error correction allow the receiver to correct data errors by transmitting or doneant information? See what does an FD eight signal report of three plus three plus three means? That means it's three times the

noise level? Yep, all right. Most digital modes on HF are transmitted as USB signals, the exception as rtt Y uses LSB modem and software must be configured for the correct moder rate receiving tone received data signal screen you know to be tuned correctly. Since PSK uses a single tone, either USB or LSB will work. Most use USB. Like other amateur signals. Digital mode bandwidth is defined by the FCC.

The bandwidth of signal changes with symbol rate. The symbol rate increases, so does the bandwidth needed for the signal needed to transmit them. Most common method of generating transmitting these modes is to connect to an audio output of a computer sound card to the microphone of a single sideband transceiver. So most time you're going to use your computer to connect the sound card connect the tune radio. Here's a chart that shows some of the bandwidths of

the different digital modes. What's interesting to point out here is like PSK thirty one and FT eight, they're fifty hertz. Why we don't send a lot of information there, but they're fifty hurts wide, so that means you could put fifty uh QSOs fifty times five. It's twenty five hundred in a you need some space, but you can put a bunch in a audio passband right. So sometimes you'll see in the FT eight modes just the whole past base is loaded, we'll sleep, so you can get a

lot of QSOs in one. It's very efficient five percent of the time. But FM modes and these digital modes, you're transmitting full power the whole time that you're transmitting, and those times those can be you know, several seconds to half amended or something, so you have to be real careful. Make sure you watch your transmitter, don't ex seed. It's average power rating, so reduce the transmit power to prevent overheating. Usually I buy about fifty percent is usually

a good idea. Digital modes can generate interference, just like phone and c W. For digital modes that use a single sideband transmitter to transmit audio FSK. Most common problem is supplying too much or too little audio from the computer to the radio's microphonium pit a waterfall display. The vertical lines represent spurrac emissions caused by overmodulation of the transmitter. ALC and digital modes Automatic level control are their use

for preventing excessive drive to the amplifier inputs. ALC circuit produces gain when power level gets too high. However, it comes at a price. The signal compression can result in distortion resist temptation to turn up gain. For digital signals, distortion caused by ALC makes the signal harder to decode create spurase emissions. It's similar to overmodulation. When in digital mode, your ALC system should be either disabled or input level and gain turned down to the point where the ALC

does not activate. So my experience operating this is or any of the digital mode. This is probably the most common airror mistake misunderstood piece by some new opera by operators they don't have their ALC their audio input adjusted right. You can turn it off. But what I do is I have mine turned on, but I have it right below where it cuts on like it, just like it says, so that seems to be the right sweet spot for me.

But you can hear you can see a station when they're really over modulating their signal, their call sign will show up four times in the FT eight pass band, right, So this is probably the most important thing to go adjust and correct is get your audio levels right coming from your from from your PC. If you're using a Windows thing, Windows sometimes does favorite things to your sound card when you didn't want it to an update or something, so always check this and make sure you got an

eye on. I always have my my ALC meter up on my so I can always see if something's going on there. ALC is a big is a big deal in digital modes, all right. It's send to some practice questions which mode is normally used when sending rtt Y signals. So rtt Y is almost always doing in lower sideband, and for the all the other digital modes it's usually upper sideband, which is bu What could be wrong if you cannot decode an RTTY or other FSK signal even

though it apparently tuned in properly. Market space can be reversed wrong boderate wrong side I think all those sound correct to me, and that is correct? What should the ALC system? Why should the ALC system be active when transmitting AFK signals? Too much ALC can cause a transmitter to I think it's B. The ALC can action can distort the signal. Why is it important to know the

duty cycle of the mode you're using when transmitting? Want to make sure you don't exceed your transmitter's average power rating or can be B. What is the relationship between transmitted symbol rate and bandwidth? Uh? The higher symbol rates require wider bandwidth, so that's B. What is indicated on a waterfall display by one or more vertical lines on either side of the data mode on an r TTU I signal, usually that's over modulation. Okay, let's talk about

in a digital mode. How do we initiate a contact? Right? So, yeah, like a voice mode, You type in C Q c Q, this is my case, K M four CJ, save it a few times, put a K at the end saying hey, I'm waiting for someone to contact me that I'm over, and then the response station would say my call sign. This is followed by the answering station's call signed with the K at the end. Modes such as pactor and VARA the software mode and will have a specific disconnect message.

But notice the K here to use at the end of a transmission to indicate the other station is to transmit as shown, so that says that I'm finished waiting on you. Right. It's like over if you connect to a gateway. The exact way you connect to the gateway depends on the equipment and the mode that you're using, but us it begins with some kind of a connect message. If the signal is received without air, there's usually a

handshaking or right. They call it training sequence and packets to help for the two stations to determine the right road the VOD in the protocol to use. Because these stations respond without a human control operator they are operating.

A lot of them are automatically run, so they have to fall under the rules of the digitally controlled Automatically Digitally controlled station rules, which restricts them to certain parts of the band and stations under FCC rules must operate under local remote control with control operator in charge of all transmissions. That's the rule. Here's where you can find on the band plan these automatically controlled digital stations are allowed to operate here. Then during the contole. A waterfall

is kind of a neat display. It shows yours all the nearby signals. This is a PSK thirty one looks like The waterfall displays a series that shows the presence of signals and the series of lines representing the scan across the frequency range. Signal strengths is represented by brightness or density or color. As new lines are captured, older lines are removed as it moves down. The slides down the screen. It's called the waterfall tuning age for an

RTTY signal. If I've got looking at an RTTY signal on a spectrum analyzer or or my audio spectrum analyzer, the vertical lines are the mark and the space. Uh those are these lines right here and help tune in, so you would tune across the band. You're going to line up your as you move this wiggly line across you want to line them up to these right here and helps you tune in the signal. There's a also you can look on a silloscope kind of thing and

see the crossed ellipse from the right. They're used to to see how well fine tuned if you're perfectly tuned, you'll see two ellipses perfectly at ninety degrees angles. That indicates how good your tuning is going. That's a pretty good looking signal there. Okay. Third party traffic. All the rules about third party traffic apply to digital transmissions. You know. That includes the information and the emails, the digital messages. If you transmitter a web page or whatever kind of thing,

third party rules still apply. Commercial messages may not be transmitted via amateur radio, so interfering signals in digital modes hidden transmitters. If I'm talking to a guy over in Europe FT eight, I don't hear I don't. I only hear him, But over in Europe he may be hearing three or four guys on the same frequency I'm on, but I can't hear them, so I may have a hard time talking to him. So that's sort of what

referred to as he's hidden to me. It's okay. The result is unintentional, but it prevents us from uh from completing the contact. Unpacket modes, packed tour or when more, they don't recover well from noisy and weak signal week environments, so you get a lot of failure If you get a lot of failure to connect or frequently tried after a long time, it may just be band conditions are too noisy, try a different band or something like that.

So here's some practice questions for this section. What's required to conduct communications with the digital station operating automatic control outside the automatic control band segments, It's gonna be a the station is shame and the contact must be under local or remote control. Same rules that apply for voice for controlling the station UH with the automatic control. And what bands may automatically controlled stations transmit RTTY or data

missions communicated with other controlled stations. I think only on the band's segment where it's permitted anywhere in the six meter or shorter wave. The bands are limited segments, that is corrected its specifically to on the six meter band on this particular one UH. These are automatically controlled stations transmitting rtt y. You know, two of them in only one place you can do it, that's the six meter band. What symptoms may result from the other signals interfering with

the pactor or VARA transmission? What symptoms frequent retries, long pauses, failure to establish connection between those all those symptoms that we've got interfer in the signals. Okay, Which is the following is a way to establish contact with the digital messaging gateway system. Uh, you don't send EMO to the control operator transmits it's a connect message is how you It's how you try to connect to them. Be deep?

What action results from a failure to exchange information due to excessive transmission attempts when using an ar Q mode? I think connection has dropped. That's correct, because they're gonna there's a time out time or you're gonna try to talk to somebody. If you're talking to them and somebody you lose connections, there's a number of retries and then it gives up. So that's that's that's me. Which of

the following describes a waterfall display? Let's see frequency is uh is vertical, amplitude is horizontal signal strength Uh, let's see signal strength time the C frequency spour is horizontal signal strength tensity. It is all vertic. Right, And that's the end of this chapter. M So you want to do another module? You want to stop for today? It's not loud and here, yeah, I think it is loud. Guy, that sounds good. I'm Okay, so that was the Okay, Our next topic we're going to talk about is UH.

Here is dipoles, ground planes and yaggy antennas. The most fundamental antenna we have in AMATE radio is a dipole UH. It's a straight conductor that's half wave linked UH along with the feed point in the middle. It's also known as a double it antenna UH. The strongest radiation direction of the dipole's broadside to its axis and a plane containing the ant and its conductor. The weakest radiation is

off the ends. The shape of asthmith pattern for a dipole and free space is shown in the next figure. And I'll show you here's the picture. This is what it looks like. Again. You've got a halfway link piece of wire feeding it in the center, stretched out for horizontally and this is the radiation patterns you can see. It has a radiation pattern broadside and to the back with a less radiation to the sides. So very fundamental antenna. Great antenna probably the most popular type of antenna we

have to using in the HF bands. Okay. Diepole is often used as a reference antenna for gain measurements. Gain is measured in DBD. Isotropic antenna is a reference antenna with a gain given in dbi. The isotropic antenna is a theoretical antenna. It's an a tenda that radiates equally in all directions. So sometimes you'll see U an antenna the performance reference to dB I or just dB with the gains. So there's a way to convert between the two.

To convert from dB D which is dB dipole the dB I, which is isotrophic, as you add two point one five dB h to convert dB I to dB D uses to subtract two point one five dB. Current in a halfway dipole is highest in the middle, that is in zero at the ends. Voltage along the dipole is highest at the ends and lowest in the middle. So if you have a dipole antenna, just remember that that the current is the highest in the middle, voltage is in lowest in the ends, and the and the

voltage is the opposite. The halfway diepole, as we see here in this figure, has its maximum current at the middle U and the maximum excuse me has a minute. It has a maximum current in the middle of maximum bolted at the end. The feed point impedance is lowest in the middle. The odd harmonics of the fundamental frequency of the dipold speed point impediance is low at the midpoint. Once again has shown So if you've got harmonics, this is what they would look like based on if it's

a half, if it's a second, third, fourth harmonic. So again the impedance is lowest in the middle for us for the this dipole, and typically dipoles about sixty eight sixty two homes. The impedance increases as a feed point is moved away from the center several thousand homes at the end. Popular antennas are in FED halfway off center, FED halfway. You'll hear a lot of those. Those are different variations of where you feed the end the antenna.

The FED as an example as popular for porta bowl operation. It's a lightweight, easy to install. It's a halfway dipole fed at one end. In free space. The half wavelength is equal to about four hundred and ninety two divided by the frequency in megahertz. This is if you want to get the linked and feet you'll generally find that the length will be shorter than the free space wavelength. Calculation However, for these exam questions you don't have to

take that into account. Just be aware that where thickness and hightabo bround influenced the resonant length and the length again in feet four hundred and ninety two divided by the frequency and wavelength. So what is the proximate length of in feet of a halfwave dipole resident of three

point five to five megahurts? How would you calculate that? Well, remember we take our four hundred and ninety two divided by three point five to five and you get one hundred and thirty nine feet, So that would be the wavelength forty meters on eighty meters. Remember the axual antenna will be a little shorter than this, But build to that calculation and use your tuner to tell if it needs trimming. Ideally you won't. You want SWR as close

to one to one as you can without tuning. So what's the approximate length and feet of a half wave dipole at fourteen point twenty five megahurts? This will be twenty meters, So remember to use your formula four ninety two divided by fourteen point twenty five and you get thirty four point five feet UH. Center fed dipoles are the easiest to use on the band which they are resident. The feed point impedance is a good match for a fifty or seventy five ONEm coax and for coacts on

odd multiples of the fundamental frequency. A dipole doesn't need to be straight to be effective. Dipole can be supported in the center, where the feed line can be conveniently attached. There's another configuration called an inverted V, where you take the ends and lower them down. As long as the legs of the dipole form an angle of ninety degrees or more. The inverted V is nearly as effectively as

a horizontal installed dipole. So how you fix your dipole, or how you based on the area that you've got to or the place you have to mount your antenna is going to determine a lot what's going to be the shape of your dipole. But don't worry too much about trying to keep it perfectly horizontally or you know, get your antenna up, tune it, get on the air. The ground plane antenna is one half of a dipole, with the missing portion made up by an electrical mirror

or so we call that the ground plane. It's made from sheet metal or screen of the radios can be excused. The ground plane can be made from metal or a screen of radial wires. Basic ground plane is a quarterwave length long, with the feed point at the junction of the antenna and the ground plane. For HF ground playing antennas at ground level, radio wires are laid on the surface of the ground, or can be. They can't be

buried within a few inches of the surface. Ground plays are called verticals because that's usually the way, uh that's usually the way they're constructed, and how you install them. A ground plane radiates the best broadside to its axis if installed vertically. The ground plane antenna pattern is omni directional, that is, its uniform in all asthmus angles or directions. Very useful for VHF and UHF mobile portable communications where the signals can maybe even where the signals they come

from any direction. Here's a here's a picture of a ground play. Again. You've taken that diepole and you've made you've made it a quarterwavelength tall, and uh, you've taken the other half of the diepole you've made that your plane now. So the ground plane, whether made of solid metal or radio wires, creates an electrical mirror the image of the quarterwave antenna. This creates the electrical the electrical

equivalent of a dipole antenna. The feed point impedance at the base of an ideal ground plane it's about thirty five omes half of a complete dipole's impedance. Because only half of the antenna is physically they're able to radiate the enter the energy. So remember the dipole center fed dipole is about sixty to sixty three ohs. The feed point and penants of a ground plane antenna with the radios perpendicular to the antenna proxy, thirty five omes resulting in a one point four to one SWR with a

fifty oem coax fee. Drooping or sloping the radios gradually raises the feed point impedance until until the radios droops so far as to become only one half of the dipole. The feed point pediants becomes seventy two oms, so a fifty O feed point is reached with radios grouping approximately forty five degrees. These are real popular for vhf uhf.

They're easy to make, and you just put your quarterway whatever your two meters or two twenty or four to forty and then do your ground radios and vend them slightly forty five degrees and they work great. You can put them in your in a closet in the attic and they're great antennas. Then a droop angle three to forty five degrees was shown in the last figure. It results in a feed point penance approximately cook approximing fifty oms.

As with the dipole, it's not useful to provide a one size fits all formula for the length of the ground plane antenna. Since the ground plane is one half the size of a diepole. Start with one half the free space length and be prepared to trim the antenna's link. So you always want to start longer than you need because once you start trimming antenna sometimes it's difficult to go back the other way. So what's what's what's the approximate length and feet of a quarterwave monopole antenna cut

for twenty eight point five megaherts. So remember a quarterwave, you're gonna use two hundred and forty six divided by the frequency, so two hundred and forty six it's a quarterwave two forty six divided by twenty eight point five eight point six feet, So a ten meter UH quarterway vertical is about eight and a half feet all right, HF mobile HF and antennas UH they're often some ford of a ground plane UH. Most popular is the vertically

oriented whip antenna for mobile operation. A full sized quarterway mobile whip, though, is really not feasible on bands below twenty eight twenty four megaherts just too long, so you often you'll see what what what they call loading. There's some loading techniques that are used to increase the electrical length. Usually sometimes you'll see loading coils, a coil added to

the base or or somewhere along the length. Sometimes you'll see what's called capacitive hats their spokes or look like a wheel shaped structure added near the top of the antenna. And then there's linear loading whereus part of the antenna is folded back on itself. So these techniques are all devised to load the antenna to make it think it's electrically longer than it really is. Another common feature of

mobile whips is the corona ball at the tip. It does add a small amount of loading capacitance, but its main purpose is to eliminate high voltage discharged from the sharp tip of the antenna while transmitting A loaded antenna is not as efficient as a full size straight whip, and we'll have a small operating band without without retuning. When you add a loading coil to an end to an antenna puts a real high que in that area

of the band that you're operating in. So if you if you've got a large band, you may have to retune it to as you've moved throughout the band because, like I said, it's it's tuned for a it's got a very narrow high queue on it. The screwdriver antenna design, which is a whip with an adjustable coil at the base, changes the inductance. It has gained popularity for HF mobile operation. Is a good compromise between performance and convenience. And you

may have seen them. There's a big coil at the base and as you've moved between the bands, the coil moves up and down, changing the inductance. Pretty effective antenna. Great, Like I said, great, great compromise antenna for HF mobile operations. So what's the effects of ground on these antennas. A dipoles feed point impedance and radiation pattern are both affected

by its physical height above ground. The feedpoint impedance is affected because the electrical image is electrically reversed from the actual dipole. As the image and antenna get closer to together, the actual antenna begins to be shorted out by the image. So below a quarter wavelength and height dipoles feed point and penis steadily decreases until it's close to the ground level.

It's going to be close to zero. So so it's important to get the ground to get the antenna at least usually half a wave length up if if, if you can. Sometimes you can't do that, and I always say do the best you can. Try to meet the you know, the guidelines, but get it, get something up, get on the air. That's the main that's the main thing.

This this chart here shows the feed point penions of a horzonal dipole over perfect ground and see it varies dramatically with the height at ground level down here to the bottom it's shorted out. Basically it's zero and see antenna moves up gradually it approaches about seventy two oms about feed point penance in free in free space above a quarter of the above one quarter wavelength impedance varies as suggested in this figure over here, eventually reaching a

stable value at a height of several wavelengths. So you know, so eventually as you get it hired and hire it finally stabilizes up here. About seventy two oms is the feed point and penance when you get it real high, so uh fifty oms. Feed point impedance you can see here is about point two wavelengths above. So this chart just shows that that the height above ground is going to change it then the feed point penance, so you

have to you have to compensate for that. High above ground also affects the radiation pattern because of reflection of the antenna's radiated energy by the ground. The direct and reflected signals take different amounts of time to travel to the receiving antenna, so they can add together, cancel each other, or any combination in between. So what happens when a dipole is raised in steps from a very very low height to more than one wavelength above ground And this

figure shows some of those. These are four or four plots at different wavelength heights above ground. As a dipole starting at at one eighth wavelength above ground is raised, the effects of its electrical ground image caused the elevat elevation pattern to flatten out at multiples of the half wavelengths. The height pattern has a null in the inverted direction because the direct and reflected signals canceled at heights below

half wavelength. The Dipolese pattern is almost omnidirectional and is maximum straight up, so the height above ground will change your radiation pattern of your diet of your dipole. There's another intendant called end VIZ, which is near vertical incident skywave propagation. These signals that these are signals that go straight up. UH signals radiated at high vertical angles on low frequencies are usually reflected back in the ground over

a wide area, ensuring good communication. Horizontal dipoles from one tent to quarter wavelength high I produce an omnidirectional high out angle pattern ideal for envis opper ideal for the envas used like the previous chart showed, when that antenna got close to the ground, you saw the radiation pattern go more up in a round ball up towards the sky. So by lowering your antenna you can change the effect of its radiation pattern and use it to bounce off

the sky and talk regionally. It's used by many public service teams. Polarization also affects the amount of signal that is lost from the resistance of the ground. Radio waves reflected from the ground have lower loss when the polarization of the wave is parallel to the ground that is horizontally polarized. Because the radiation pattern is made up of reflected waves, Combining the direct waves that are not reflected reflection loss results in stronger maximum signal strength. So here's

some antenna terms. Feed point impedance that's the ratio of RF voltage to current and an antenna speed point resonant. When an antenna feed point impedance is completely resistant with no reactants, we talked about that yesterday. A little bit radiation pattern graph of antennas signal strength in every direction or at every vertical angle. That's a radiation pattern. The as myth pattern shows signal strength in the horizontal directions.

Elevation patterns shows signal strength in the vertical direction. Lobes is a region in the radiation pattern where antenna is radiating a signal. Okay, that's the lobe, and then the nulls are the points at which radiation is that it's a minimum isotropic antenna radiates equally in all possible directions. Omni directional antenna radiates a signal equally in every horizontal direction. A directional antenna radiates provincially in one or more directions.

Gain is a concentrated transmitted or received signals in a specific direction. Front to back ratio is a ratio of gain in the preferred or forward direction to the opposite direction, and front the side ratio is the ratio of gain in the preferred or four direction to directions at right angles. So those are some antenna terms that that that you will run into you if you look at an antenna spect some some of these things are spect out there and some of these things depending on what you're trying

to do. These are important things that you'll need to consider choosing and the type of antenna that you want to use. Okay, what's the purpose of a capacity's hat on a mobile antenna? Do you remember that's the little ball that's up at the top of the vertical. Its primary it's primary thing is to u to increase the power handling capacity of a whip. Nope, that's not it

reduced raition resistance to electrically LinkedIn. It's physically shorten the antenna to lower the variation angle have to be c but its primary purpose remember too, is to static discharge. What is the purpose of the corona ball. The same thing on the HF mobile antenna, and that's to reduce RF voltage discharged from the tip of the antenna while transmitting D So what is one disadvantage of using a shortened mobile antenna as opposed to a full sized antenna.

Let's see, that's the operating bandwidth may be very limited, right because usually you don't have a full size antenna. You get your gonna going to shorten it. And to make it too, you used to put a coil in and that's gonna really affect where you can operate in that particular band because it's a high Q circuit, which is the following is a common way to adjust the feed point impedance of an elevated quarterwave ground plane CLI

intendent to be approximately fifty OS. Remember we talked about there. This is where you take those ground radios. We've got a vertical now. And if you bend them, if you bend them down just a little bit, uh, bend them slightly downwards, Uh, that will help raise the input, the the raise the impediance. So it's which is the following best describes a radiation pattern of a quarterway ground plane vertical antenna, so about a quarterway round plane, and it

is it's omni directional. What is the radiation pattern of a dipole antenna and free space and a plane containing the conductor? Okay, so that would be it's a figure eight at right angles to the antenna. So you're you remember it's the radiating is broadside to the antenna up, not broadside, but forward and back to the anti antennae. It's antenna itself. How does antenna hype affect the asthmathyl radiation pattern of a horizontal dipole HF antenna at elevation

angles higher than about forty five degrees? So this is how does the height affect it? The antenna is less than a half wave link of that's sort of the key point. Hi, the asthma pattern is almost omni directional. You get lower than that, it starts flattening out. So see is the answer. Where should the radio wires of a ground mounted vertical antenna system be placed, let's see, on the surface or buried a few inches below the ground. So if you do in the parks, not in the air,

lay them on the surface of the ground, that works. That, That works great. If you've got a permanent inflation at your house, you may want to bear them a little bit. You don't run open with the lawn with the lawn more, but don't bear them, don't bury them too low. How does the feed point impedant of a horizontal half wave dipole attended change as the antenna height is reduced to

one tenth of its wavelength above ground? Okay, so if you as the the feed point is going to change, it's gonna get it's gonna decrease as you change the height. When you it it comes closer to the ground, the few point pens is gonna get. It's gonna get lower. Eventually get on the ground, it goes to zero. How does the feed point pence of a halfway dipole change as the feed point is moved from the center towards

the end. So the feed point penance you remember of a center fed dipoles around sixty something else, the more you move it off of the center clos to the edge, it increases. So the a the impediance of an infed diepoles about twenty five hundred homes off center fed use the quarterwave, then it's about two hundred or two. It's about got about two hundred homes. So as you go from the center to the end, the few point pace increases. Which of the thowing is an advantage of a horizontally

polarized as compared to vertically polarized antenna. Lower you have lower ground losses. What is the approximate length of a half wave dipole antenna cup? For fourteen point twenty five, So number's four ninety two divided by fourteen point twenty five, twenty meters is going to be about thirty three feet.

All right, there's there's the equation four ninety two divide by fourteen point twenty five, it's thirty four point five, So thirty four point five in an answer, But you're gonna you're gonna get the closest one, which is D three. What is approximate wavelength of a half wave dipole antenna cup for three point five to five, it's going to be about one hundred and thirty two feet, all right, so remember take fortety two divided by the frequency to

the half wave length that's going to be answered. Okay, how about we got a quarterwave. Now, remember just sitt in a halfwave, so it's not four ninety two, it's a quarterwave. So it's going to be two forty six divided by the frequency. In this case it's about eight feet. So when they ask these questions, you got to are they ask them for the halfwave which is four ninety two or the quarterwave which is half of that two forty six? So keep that in mind when you see

this question. Are they asking for the halfwave or the Quarterwavey? How does antenna gains? State it in DBI compared to the game stated in dB for the same antenna. So the relationship is two point one five dB. But is it higher or or or lower? And this in this case it's actually higher. How does an antenna gain if you have a DBI antenna compared to a DVD which is a dB dipole, it's two point one five higher.

Which of the following antenna types will be most effective as a near vertical incident skywave in is antenna short skip communications on forty meters during the day. Okay, horizontal dipole places one hundred and ten to one quarter wavelength above ground, a quarter to a half half above it's going to be a horizontal dipole, and it's going to be Remember, the closer you get to the ground, the more the radiation patterns is elevated up, so it should be a here it is, so let's ten a quarter

wave to a tenth. Closer you get to the ground, the more radiation is going to be reflected up to the sky. Okay, what is the feed point impedance of an INFED half wave antenna. Let's see INFED is going to be two twenty five hundred homes, so we'd say very high in this case. D How does a screwdriver mobile antenna adjust its feed point impedance? It varies the loading with an end with the inducted so you'll see a coil at the bottom and it moves up and down.

That coil is an is an inductor, so will be it varies in the inductance B. What is the common name of a dipole with a single central support. It's the inverted B configuration. Okay, let's talk about yaggy antennas. Directional antenna just create gain as well as rejecting interference and noise from other than the desired direction. By aiming your antenna in the direction shown in the asmithal projection map, you'll be beaming your signal directly at the other station.

So as you point your antenna, that's the direct On a yaggy antenna, the where you point it, that's the direction your energy is going. Dipole, ground plane and random wire antennas use a single radiating element, but a dipole is an arrayed antenna. It uses two or more elements to create a maximum field strength in a specific direction. It's called the main lobe or major lobe of the radiation pattern. Two tie of arrays. There's the driven pair

and parasitic and a driven array. All the antenna elements are connected to the transmitter and are called driven elements. Parasitic array one or more of the elements are not connected to the feed line but influence the antennas patterned by interacting with the radiated energy from the driven elements. Whether an array is driven or parasitic, it creation pattern is

determined by the constructionive and destructive interference. If in phase, they will reinforce each other, out of phase, they will cancel. Most popular of all direction antennas is the yaggy because of its simple construction and good performance. Yaggy is a parasitic array with a single driven element in at least one parasitic element. The driven element is a resident dipole

approximately halfwave length long. Parasitic elements placed in the direction of the maximum gain are called directors and the and are slightly shorter than the driven element. Parasitic elements in the direction of the minimum gain are called reflectors and are slightly longer than the driven element. The front to back ratio is the ratio of signal strength to the peak of the radiation patterns major lobe and that it and that to that and the exactly the opposite direction.

So the front to back ratio is how much energy goes forward versus how much energy goes back. Okay is two element yaggy shown in this picture. Here with a single parasitic element, you can see we've got a driven element here, that's your dipole. You've got a director, this is the direction of radiation, and you've got a reflector in the back. So this is the way the antennae is obstructed, the way that it works. Yaggy design trade offs.

Primary variables for Yaggy antennas are length and diameter of each element and their placement along the boom of the antenna. These affect the gain s WR front to back ratio in different ways. The more directors you have this increases the gain. A longer boom with the fixed number of directors increases gain up to the maximum length, beyond which gain is reduced. Larger diameter elements reduce SWR variation. With frequency placing and tuning of elements effects gain and feed

point impedance. So all those factors come into play when you're trying to design your and your antenna. There are other general rules of cause and effects, but these are typically on decision of the antenna designer yourself. But when you go purchase Yaggy and Yaggy antenna, someone has already figured out the size of the beam and the size of the directors, and the parasitic elements, and you'll buy it based on front back ratio in the game that you need, going in the game that you are desired.

Most shaggy designs have desirable radiation patterns also have a feed point impedance somewhere below fifty oms. With regular coacts with the feedpoint impedance from twenty to twenty five oms, this results in an undesirable SWR two to one. So the most common technique for matching the impedance is a gamma match. A gamma match is a shortened section of parallel conductor transmission line that uses the driven element as one of its conductors. Transmission line transforms the low impedance

of the feed point to a higher value. An adjustable capacitor, either an actual variable capacitor or a shorter piece of insulated wire inside a hollow gamma rod is used to adjust the gamma match for s WR one to one. A mechanical advantage of the game a match over other techniques is that the driven element needed needs not to

be insulated from the boom, which simplifies the construction. UH there's a beta match, which or sometimes reference as a hairpin, is a short length or stub a parallel conductor transmission line connected directly across the driven element feedpoint. The stub acts as an inductive reactants that can compensate for any capacity of reactants at the feedpoint. The balance is used to maintain the electrical balance between both halves of the

driven element. Other techniques such as the Omega match and penis transformers and transmission line subs are also described, and you can read those in the ABRL handbook. Here's some practice questions. Which of the following describes an as methyl projection map? Okay, the map that shows the actual land mask says, wouldn't be that. It's going to be a

map that shows the bearing distance for specific location. Okay, So that when you bind a yaggy antenna member, it's gonna it's gonna project and as anthyl projection in the in the four direction. Uh. Which of the following would increase the bandwidth of a yaggy and antenna larger diameter elements? Uh?

The spacing is is uh is has will affect the gain and the impediance, but the lord of the element size actually helps with the band with the with with the bandwidth which is approximate link of the driven element of a yaggy antenna, that'd be a halfwave link. Remember it's a The driven element is a dipole, so it's half wave length. Uh. How do the lengths of the three element yaggy, reflector and director compared to that of the driven element? Uh, the reflector, let's see, the reflector

is going to be longer. Director's gonna be short. Its like it's gonna be a here. Yeah, he's the answer. So the usually the so so the director's right behind the driven element, towards the back of the antenna, it's a little bit longer. And then in front of the driven element. What's the primary effect of increasing bloom lengths and adding directors to the and to the yaggy antenna?

You're going to increase the game. Kay. What does front to back ratio mean in reference to a yaggy and it would be the uh power radiated in the major lobe compared to the opposite direction. Okay, So it's the ratio of how much power goes forward to that to the radio power forward versus the radio power in the back. What is meant by the main lobe of a director of a direct directive directional antenna? It's the direction of which the maximum field strength from the antenna is radiated.

It's it's that is that direction. So the main lobe on a yaggy is usually on a yaggy is where is where the elements where the the antenna is pointing out to the front of the antenna. Which of the falling can be adjusted to optimize forward gain, front to back ratio or SWR bandwidth of a yaggy antenna, length of the boom, number of elements spacing all those things deep. What is a beta or hair painting or or hair

pin match. It's a shorted transmission line stub place at the feet point of a yaggy antenna to provide impedance matching. So it's it's a way to remember the the yagy itself is about twenty five homes. He needs something to raise the impedance up. Its about fifty oms of your to to your system. And the beta or hair pin match is a transmission line stub that that that that does that transformation for you. Whatis is the fallowing is a characteristic of using a gamma match with a yaggy antenna.

A Let's see, it does not require that the driven element be insulated from the boom. Our next section, we're going to talk about loop antennas, specialized antennas, and feed lines. So what's a loop antenna. It can be a circular, square, triangular, or any simple open shape that is not too narrow. Feed line can be attached at a break in the loop, or a small loop can be used to a couple RF energy to the main loop. Square loop with each leg a quarter of a wavelength long is called a

quad loop. A triangle or delta loops are usually symmetrical, each leg a third of a wavelength long. A one wavelength loop acts electrically like two dipoles connected in the end, with the open ends brought together circumforts much larger than one wavelength. Typically a current patterns around loop have more than two peaks and knowles. This results in an essentially omni directional pattern, with the peak angle radiation somewhat lower than a dipole at the same height. There's quad and

delta loop beams. Popular variation of the yaggy antenna uses what's called quad loops for elements. It's called a quad It has two or more full sized loops mounted on a boom. Quad or delta loop. Beam driven elements are approximately one wavelength in circumference and operate on the same principle of re radiation and face shift as does the yaggy. The driven element of a quad is about a quarter wavelength per side, and of a symmetrical delta loop about

a third of a wavelength per side. Quad and delta loops reflectors are about five percent longer in circumference than the driven element, and the directors about five percent shorter. Front to back ratio is generally better for the yaggy. It's usually better for the yaggy. Right. Here's the figure. Here is showing a wavelength of the loop antennas. So this is your antennas. Here the square, and this is

what the pattern looks like. The direction of maximum signal is broadside to the plane of the loop, whether round, quad or delta or orienting the loop vertically aims and maximum signal towards the horizon, which is good for deep which is good for DX. So full way of blue antenna. I've got a full wave blue antenna that I use one hundred and sixty meters. It's not up very high, so uh, but that's the high side that I could get it, but you know, one hundred and sixty countries later,

I think I'm pretty happy with it right now. So talk about small loops. When the circumference of the loop becomes less than a third of a wavelength, the current in the loop becomes relatively uniform all the way around the top, which causes so small loops cause radiation patterns to develop sharpnols the broad side to the plane of the loop. Small loops in wide use. They're in wide use as receiving antennas and portable or low profile transmitting antennas.

The sharpnel broad side to the loop makes them effective for direction finding. This is typically small loop. Now they have a very high Q. Sometimes they're difficult to tune. Some have an automatic tuner that comes with them, which is great, but they're very high Q. They're very high Q antennas halo antenna which is double bent into a circle or square called the squalow with the ends separated by a small gap. Not a continuous loop, but otherwise

viewed as a half wave loop. Usually they're horizontally mounted horizontally so they produce an omnidirectional pattern, with the horizontal pattern preferred for VHF week signal operating halos for six and two meters can be mounted on a vehicle for mobile operations. Well, which direction is the maximum radiation from a VHF UHF halo antenna. That would be omnidirection in the plane of the of the halo. In which direction or or direction does in an electrically small loop less

than one tenth of a wavelength. That's circumference. Have nols and his radiation patterns, and that's broadside to the loop. Talk about some random wire antennas. It's not practically always to have a half wave or a quarterwave long resident antenna. A random wire can be used instead, connected directly to the output of the transmitter or tuner without a feed line.

This may result, however, you gotta be careful. Ray eight RADI eight random wire antennas may result in significant RF currents and vultures at the station equipment r F burns. They can give excellent results on any band for which the transmit or tuner can accept the feed point impedance. Typically got to have a tuner with these because they're

not because they're not resonant. You can stack antennas stacking antennas vertically or horizontally results in more gain and more and as more and more directors are added, the beamwidth of the main lobe angle between points on the main lobe, which gain is three dB or less than maximum narrows. Vertically stacking antennas increases gain and narrows the elevation bandwidth.

Both vertical stacks with the antenna directly above each other are spaced about half of a wavelength apart space half wavelength. Additional gain for vertical stack of two horizontally polarized beams is about three dB. You can double your power by adding another antenna on top. There's an example of of a horror of horizontally stacked and vert stacked. So stacked the antennas produces more gain in the main lobe, and two yaggis are stacked vertically at the same mass. So

here's an example vertical stack horizontally stack. Another antenna called the log periodic antenna. TV antennas are often log periodics. Log refers to logarithmic and periodic means the spacing of the elements, which is referring to the spacing of the elements along the boom, the link and spacing of the

elements increases. Logarithmic logged rhythmically from one end to the other's designed to have a constant radiation pattern in low s of R over a wide frequency bandwidth as much as ten to one, meaning the log periodic can be used over several bands. Not as much gain or front to back ratio as a yaggy antenna, but wide band multi band okay, and a log periodic antenna looks like this. It's the log pre dipole array consists of dipoles fed

by common feed line that alternates polarity between elements. Traditional TV antennas sweep the elements slightly forward. Beverage antennas was invented by Harold Beverage. They're designed not to have high gain, but to reject noise and interfering signals that are not

from the desired direction. Results in lower signal strength but a better signal to noise ratio to referred to as a traveling wave antenna, it consists of a long, low wire, usually less than twenty feet high, aligned with the preferred signal direction. They're used exclusively for direction receiving on MF and lower HF bands. Forty meters and longer wavelengths. It's high ground losses, and it has high ground losses and

is too inefficient for use as a transmitting antenna. It's a great receive antenna, like I said, and it can it can improve your signal to noise radio ratio by rejecting some of the noise. Here's an example of the beverage antenna, usually one to quarter one to four times wavelengths easily kind of close to the ground. It has a terminating resistor. That's why it's not great for transmitting, because it's gonna absorb all your energy. But it's a

great receipt antenna. And you can see by the pattern there it's it's got great rejection to the back. Okay, So signals arriving from the direction of the terminating resistor which is pointing towards the back and douce a traveling voltage wave along the wire. It gets transferred to the feed line and the feed points signals arriving from other directions or either broad side of the terminating resistor or do not induce voltage waves on the end on the

and the antenna. So a lot of people use these for you know, a lot of your radios have a received antenna, and this is one. This is an example where where you want to hook that kind of of of of of antenna in. Okay talk about multi band antennas, but Hams generally mean by multi banded antenna is the design that reconfigures itself electrically for each band of operation. Those basic multi band antenna is a trapped dipole. Each

trap is a parallel l C circuit. Resonance acts like an open circuit below residence like an adductor, and above like a capacity. And we we went through that and we talked about ls and sea circuits, tank circuits. At lower frequencies, the traps and inductance to the antenna make the antenna look electrically longer, and at higher frequency, the capacity of electrically shortens the end the the the antenna.

Usually you'll see these on a bean antenna. It's got several traps, and these traps again make this the antenna think it's you know, sixty something feet long and it's really only twenty five feet long or something like that. So they're used quite a bit for bean antennas for H for H for HF because you practically couldn't put a big yaggy up at forty meters it'd be super long, heavy high. So these antennas work pretty good, pretty popular for the HF bands, and they worked very They worked

very very well. Again, you got one antenna that operates over multi bands. Trapped diepoles is another one. The lowest frequency of operation of an antenna acts like a regular diepole. It can be shortened by the inductance of the trap. Yaggys can also use traps to work on several bands. Three element tri band yaggy with traps and the elements works well twenty fifteen and ten. So sort of like what we just looked on the previous chart that was a a yaggy with traps in it. Some drawbacks with

traps because it works on multiple bands. It radiates harmonics and spurious signals also, and uh so you've got to make sure that you've uh that that you get that you've got your transmitter tune right and uh to watch your spur you signals. Traps lose losses reduced the efficiency of the of the of the antenna. They are coil and they will absorb some of your and your your your energy and they don't radio as well as a

full sized antenna. But it's a it's a great compromise. Hey, what is the characteristics of a random wire HF antenna connected directly to the transmitter. Let's see it make cares magnificant RF current. That's a that's what you gotta be careful for. You gotta look out for because you're you can have highest of br on the thing and gotta

be careful in free space? How does the gain of three element UH horizontally polarized jaggy antennas vertically space a half wave length apart typically compared to the gain of a single element. So, as we talked about, if you can stack two of them vertically, you get about a three d B gain should be b yep. What's the primary function of antenna traps and it's two to enable multiban operation. What is an advantage of vertical stacking of

horizontal polarized yaggy antennas spig selection simultaneous? It narrows the main lobe in elevation, that's correct. Which of the following is an advantage of a log periodic and antenna h H it has wide band will bands? Okay, which of the following describes a log periodic antenna. Let's see element spacing very logged medically along the boom. That's correct. Game varies, sorry, so it had to be eight. Okay, the element spacing

is logarithmically related. What is the primary use of a beverage antenna directional receiving antenna for a for HF bands. I think that's the right answer. Remember that's the one that's got to resist her in it, and it's not good for transmitting, but it's great for receiving, and it has uh some directional to it, which is the following is a disadvantage of multi band antennas must be used. It must be fed ah uh poor harmonic rejection because

the resonant. So if I've got a twenty forty multi dipole and I'm on twenty meters, will I'm also generating a forty meter harmonic too, So you got to be character and him because that harmonic will be resident on one of your of your antennas. Okay, let's talk about feed lines and characteristic compedants. Bounce feed lines the system two parallel conductors separated by instantly material in the form

of strips or spacers. They have different characteristic impedances that characterize how electromagnetic energy is carried by the feed line. For parallel conductor feed lines of radius of conductors and the distance between them is determined by the Z which is the impediance. Most common type is window line. Typical impedance for a window lines about four hundred and fifty ohms, some as low as four hundred most common character verst of coaxial feed lines UH fifty homes and seventy five homes.

Here's an example of some of the different types of feed lines. This is UH. Yes. See here's a seventy five O twin lead four and fifty on window line. Coacts with different kinds of dielectric materials, different kinds of shielding. A lot of different UH types of coax shielding is available and insulting materials, and so you have to you

have to UH pick the UH coax UH. If you're using coacts, you want to pick the get the impedance that you want, get the jacketing, get the shielding that you want, get the UH jacketing material that you need. If you're variant outside, it's going to be in sunlight. A lot of factors to consider. Themen picking at your coax and your and your feet in your feed lines. So right, so's talk about fording reflected power and SWR. Feed line transfers all of its power to the antenna

when the antenna feed line are matched. If the impedances don't match, some of that power is reflected back and reflected by the antenna back towards the transmitter. So we have forward power, it's power traveling down towards the antenna and reflected power power that's reflected back. Power in a feed line is reflected at any point at which the impedance of the feed line changes, so that cannot necessarily be at the antenna, but could be at the connector.

Or you've got an interface coming out of your shack to the out to the outside a patch panel. Whenever that feed line is interrupted or changes, the impedance can change through that and you can get a reflection there. SWR the waves carrying forward power and reflected power from stationary patterns inside the feed line. It's called SWR. It's is called standing waves. The ratio of the peak voltage in the standing wave to the minimum voltage is called

the standing wave ratio. Standingwave ratio measures how well the antenna feed line and impedances are matched. One to one is a perfect match, none of the power is reflected. SWR of infinity in the case that all the power was reflected, and SWR is always greater than one to one. For example, you always say three to one, you won't say one to three. One to one's perfect, So there's never a perfect system, so always gonna be a little greater than one to one. So how do you calculate SWR?

SBR is equal to the ratio of the high of the higher of antenna feed point impedance or feed line character's competence to the lower. So example, what is SWR in a fifty feed line connected to a two hundred load, Well, that would be two hundred divided box four, so i'd be four to one. What's the SWR and a fifty on feed line connected to a ten o load fifty

divided by ten five to one? So remember you're always it's gonna be the ratio of the higher one to the lower one, right, So you're not going to get a number less than one. Okay. SWR can be measured anywhere along the feed line. However, However, it's most most commonly measured UH at the connector at the connection to the trend to the transmitter UH SWR measured by an

SWR meter, also called the bridge. Transmitting equipment is designed to work at full power with an SBR at the input impedance feed line of about two to one or lower. Antennas that are much too short or too long will not work well. We'll have extreme feedpoint impedance causing high SWR matching feed line and the load. The antenna impedances eliminate standing waves from reflected power and maximize power delivered

to the load, but not always practical. The impedance matching is more often done at the transmitter end of the feed line. Devices used to reduce SWR called impedance matchers. Transmatch antenna coupler and antenna tuner tuners do not tune the antenna at the amplifier thinks it's got a good match out there, so in other words, an antenna tuner increases the power transfer for the transmitter to the feed line. So if you've got a bad antenna, still a bad antenna,

all right, So impedance matching. These are devices constructed from inductors and capacitors that are adjusted by the operator. A T circuit can match a wide variety of impedances at the feed line connection to fifty homes that matches trans output penians. It's important to remember that the SWR in the feed line between the impedance matching device and the antenna does not change The device just changes the load going to the transmitter SWR. The feed line stays the same, okay.

So if you've got highest WR with your tuner, you've still got highest WR on the other side of the tuner, okay. But your transmitter is going to put transfer as much power as it can to the load. So a T network usually consists of two capacitors and in an inductor, and then there's a let's see the PI network okay, so installed at the transmitter into the feed line. A T network is designed to be used with unbalanced coaxial feed lines. This circuit uses two variable capacitors and one

variable inductor. To use balanced feed lines such as window line. The output of a T network can be inductively coupled to the output, so that need either of the feed line conductors is connected to ground. Now, feed line losses feed line dissipates a lot of energy, disipates a little of the energy that's carried as heat, called attenuation or loss. Loss in the feed line is measured in DB's per unit of linked, usually specified as dB per hundred feet.

The loss increases with frequency for all types of feed lines. The smaller the cable diameter, the higher the loss. Increasing SWR and a feed line also increases the total loss. The higher the feed line loss, the lower the measured SWR will be at the input to the line. A lot of people don't realize how much loss they have in their coax feed system. If you've got like we I think we had in our earlier talking about about dv A one dB loss is you're going to lose

twenty percent of your power. So if you had one hundred watts with the one dB loss in your cable, put ad watts to the antenna and you that other twenty watts is dissipated as heat in the PAX feed line. Okay, so what's the purpose of an antenna tuner? Reduces the SWR to the feed line, reduces sw articipation increases power transfer from the transmitter to the feed line. It's going to be c You may want to think an antenna tuner. A lot of people say it reduces the SWR. Well,

no it doesn't. The antenna and the SWR on the other side of the antennaituner. The SWR is still whatever it was before, you know. So it just makes the antenna. It makes sure antenna allows antenna to transfer as much power as it can to the feed line itself. Which are the following factors? Determines the characteristic impedance of a parallel conductor feed line? See the distance between them b A between the centers of the conductors and the radius

of the conductors themselves. What is the relationship between high SWR and transmission line loss uh let's see yep. Highest WR increases loss in a lossy transmission line. What is the nominal characterist competence of window line transmission line? It's about four hundred and fifty oms. What causes reflected power at an antenna's feed point that'd be a difference in the feed point line impediancy antenna feed point line intendants uh an ten of feed pointing impedance, mismatch in impedance.

How does the attenuation of quaxio cable change with increasing frequency. Okay, so the higher the frequency, the more loss you're going to have. So intend so the uh antena and is TENU increases, so it would be B. And what units is RF feed line loss usually expressed? It's usually in dB per hundred feet D. What must be done to prevent standing waves on a feed line connected to an antenna? Not a number, not B, C B D. Antenna feed point penis must be matched to the characteristic competence of

the feed line. If the SWR on an antenna feed line is five to one and a matching network at the transmitter end of the feed line is adjusted to present an SWR one to one to the transmitter, what is resulting sw R of the feed line? And it would be five to one. So B what standyway ratio results from connecting a fifty oero feed line to a two hundred er resistant load will be two hundred divided

by fifty to be four be four to one. What sanuay racial results from fifty on feed line to a ten ole resistant blode, this case will be fifty divided bout ten five to one. All right, now we're going to talk about the ionosphere. The sun and scatter modes. So the ion a sphere. Uh, it's what's called it's the upper reaches of the atmosphere. It gets thinner with distance. It begins about thirty miles above the earth. It's remaining

gases thin, it's enough for ionization to occure. The region of the atmosphere becomes very it becomes a very weak conductor. And you can see here that it's actually three layers. There's a D layer closest to the earth about thirty miles up, the E layer, the F one, and the F two. The F one and the F two combined at night, so it's just one F region at night, and the D and E layer disappear at night. Okay,

So related to the sun, all right. The D layer thirty sixty miles is only present when illuminated by the sun. It disappears at night because ions and tree electrons are close enough together to recombine quickly when no UV is present, returning it to a neutral condition. At night, the D and E regions disappear, and the F one and F two regions combined to form a single F region. Okay, So again, the ionosphere consists of several regions of ionized

particles different heights above the earth. The E layer sixty to seventy miles above the earth acts similar to the D layer. It's higher and less dense than the D region, and it enables it to last a little bit longer after sunset. The F layer one hundred three hundred miles above is the least dense of the three layers, and

it remains partially ionized at night. During the day, the F one region splits into F one and F two during at the height of the F region varies quite a bit with local time, season, latitude, and solar activity, so it changes based on those things. At any particular location, the stronger the illumination from the sun, the higher the F two layer will be, so it's maximum height is reached at noon, when the sun is overhead and the

asphere refracts radio waves. It's a weak conductor. Refraction amount leads depends on the amount of ionization and wave frequency. The higher the ionization, the more the refraction. The lower the frequency, the more the refraction, so HF signals relatively good refraction are reflected back to the Earth's surface. VHF and UHF signals essentially have no refraction. Remember, frequency is related to what gets refracted okay VHF okay, So each reflection.

Each reflection is called the hop and it allows signals to be reached hundreds or thousands of miles away. It's called skywave propagation via the ionosphere, so it's called skip. So skywave propagation via the iosphere is called skip. The E layer acts similar to the D layer oop. Sorry about that, went to my next chart. The higher the region from which the reflection takes place, the longer the hop. Waves reflected from F two layer travel at twenty five

hundred miles before returning to the ground. Hops from the E layer a shorter, about twelve hundred miles, and some combinations of frequency and iization level result in weak bending. The wave must leave the Earth surface at a low enough angle for the binding of the wave to be sent back. Highest takeoff angle at which a wave can be returned to the Earth is called the critical angle. Critical angle depends on I spirit ionics, spirit conditions, and frequency.

Radio waves are reflected and bent in the ion spere, so they return to Earth far from the transmitting station. Without refraction in the ionosphere, radio waves would pass directly into space. So I've got a station over here it's transmitting hits the ionosphere at the correct angle and reflected back to Earth, and a station on the other side of the Earth canton here. If the there's a critical angle,

we'll talk about the critical angle over here. Waves that leads the transmitting antenna above the critical angle are refracted in the ionosphere, but not bent towards the return to the Earth. It's at and below the critical angle will return to Earth. The lowest angle return waves that return to the Earth at the greatest distance, which is why low angles of radiation are often best for d X stations.

So depending on how your signal is, the angle of which it takes off from your station depends on does it get reflected reflected back or not so, and this is called the critical angle. Here, the critical angle the critical frequency is the highest frequency at which waves transmitted straight up will return to Earth. Okay, absorption uh. The enemy of propagation is absorption UH. In D and E regions, waves passing through the dense the denser gases are partially absorbed.

The D region is not good is not very good at refraction and HF bands below ten megahertz a M broadcast bands and at lower frequencies the d region completely the absorbs radio waves during the day, preventing those waves from returning to Earth. Absorption increases in daytime and when solar UV is more intense. When is the best time to transmit on HF below ten megaherbs, It's gonna be

at night and AM radio stations. That's why they can run the high power during the day, and when the sun goes down they have to reduce their power because during the day all their energy is getting absorbed, so it's not going other than locally. But at night it would it would bounce off the f layer and would be it would be a big problem. Noise Noise is another enemy of propagation. It covers up weak signals, stronger at frequencies below VHF. Lower you go in frequency, the

stronger the noise or static. It varies seasonally, most noticeably on lower frequ the hsvams in the summer, when atmospheric noise is the strongest I know around here. In the afternoons, a lot of thunderstorms around the area across the state, and staticky long path and short path when iyosphere a long short path does not support propagation. Sometimes long path will occasionally propagation over long and short paths will be supported at the same time. Unless the paths are almost equal,

there will be an echo or delayed. Signal arrives a fraction of a second later. In my experience, I've done this a couple of times. I've heard my signal go short and long path and there is a little echo delay. It's a cool thing that happens, and you get all excited about it. But it's a pretty cool. It's amazing phenomena around the world propagation. You can hear your own signal coming all the way around your location about one seventh of a second later, So conditions are right. It's

a pretty cool thing. And this catch shows the Earth both has both great circle paths drawn between the two stations. So here I've got this is your station, and you transmit and it goes all the way around the Earth and comes to that station or short path is here, this is long path, and this would be short path this way, And like I said, sometimes I can hear you can hear your signal come all the way back around.

Kind of cool. Okay, how is a directional antenna pointed when making a long path contact with that other station, it would be one hundred eight degrees from the station's short path. See like, if I'm trying to go here to Texas, I point towards the I guess towards the west. If I'm trying to for a short path for long paths, I point towards the east. If I can come all the way back around. What is a characteristic of skywave signals arriving at your location by both short path and

long path. Let's see periodic feeling its light echo might be heard d. What is the approximate maximum distance along the Earth's surface normally covered on one hop using the F two layer, It's about twenty five hundred miles C. What is the approximate link distance of the Earth's surface normally for one hop using the E region, It's about twelve hundred D. What ion expirent region is closest to

the Earth's surface That would be the D region. Ay, what is meant by the term critical frequency out of given incident angle highest frequency which is reflected back to Earth? That is the answer? Hey, why is skip propagation via the F two region longer than via the other I experienced regions densis highest because it's the highest c's the F two layer is the highest layer that we have is the furthest away. So what does the term critical

angle mean as applied to radio wave propagation paths? It would be d the highest takeoff angle that will turn the radio wave to Earth under specific ionospirit conditions. There websites you can go to during the day that give you critical angle and frequency and changes of course as the sun changes, as there are places you can go look at the propagation. Why is a long distance communication on forty sixty eighty and one hundred and sixty years

more difficult during the day. That's because it gets absorbed by the D region c O, which ionic sphirit region is the most absorbent of signal levels below ten megahertz during daylight hours. That would be the D region. Okay, sunspots and sun cycle, let's talk about the sun. I Hones sphere is dependent on solar UV to separate electrons from atoms. Much of the variation in UV radiation is

due to sunspot activity. One complete sunspot cycle lasts about eleven years, when more sunspots are observed more UV is being generated, creating more intense ionization, improving propagation on higher frequency bands above ten megahertz and even into the lower VHF region. Here's a graph that shows the sunspot cycles over time, and E said, it's about eleven year cycle.

We've just come off. I guess our peak cycle, and it's been it's been fund in mid twenty twenty three when this book was published, cycle twenty five was heating up and propagation on ten years and other bands was increasing at peak cycle. There may be sufficient solar UV to cause higher frequency bands ten meters, for example, to stay open for long distances during contacts at night. High ionization negatively impacts low frequency bands age sixty meters because

it increases absorption when solar activity is low. Lower HF bands have good propagation, and higher HF bands above twenty megaherts fifteen meters and up often are often closed. One band that seems to do well at all times and sunspot cycles is twenty meters fourteen megaherts. It supports daytime communication worldwide nearly every day, and that's true twenty meters you can always almost always find something going on twenty meters seems to be the sweet spot. And here's a

chart showing the propagation on the different bands. What happens during the day, what happens during nighttime. So the bands I mean dear deer during the day, the low the low bands are fairly quiet. You can do regional communications in the state of Alabama. We can talk regionally. Uh, when we're doing our areas activities during the day, we can can usually community we can communicate. So based on

the time of day and the band you're on. And once you get your general license and start getting to the operate on the HF bande, you're gonna learn all these things here. You're gonna experience them. You're going to become an expert on propagation, when to when to communicate, where, what bands are good. It's a whole lot of fun. Okay. Sun spot's also seem to move across the Sun's surface

because the Sun rotates once every twenty eight days. That is why propagation conditions good and bad on the HF bands often repeat themselves in a twenty eight day cycle as sunspots rotate back into the From Earth. Measuring the solar activity, you can there's a you can measure the number of suns of sunspots. There's a thing called the solar flux index. It describes the amount of twenty eight hundred megahertz radio energy. High levels indicate high solar activity

and better HF propagation of O ten megahertz. A thing called the K index has a value from zero to nine. It represents the short term stability of the Earth's magnetic or geomagnetic field. Higher values indicate geomagnetic field is disturbed, which disrupts HF. An a index gives a good picture of long term geomagnetic field stability, and it ranges from zero stable to four hundred greatly disturbed. It's calculated from

the K index. And there are sites you can go to that have this informational real time And so LOO activity is so important to propagation and communication that is monitored constantly. And like I said, you can go to certain websites and get these values and the information on the sun. Okay, So, how does a higher sunspot number affect h of propagation and answers? A higher sunspot number generally indicate a greater probability of good propagation at higher frequencies.

Which is the following are least reliable for long distance communications during periods of lower solar activity. That would be fifteen meters, twelve and ten. That's what we've got, So we've got low solar activity higher bands. What is the solar flux index? It is the measure of the solar radiation at the ten point one seven centimeter wavelength band. At what point is the solar cycle? Does the twenty meter ban usually support or worldwide propagation during daylight hours?

Usually it's all the time. D It's truly not affect. I mean, it's effective, but it usually does fairly well. Twenty meters of the place you can usually go to and find some activity no matter what time of day. What causens HF propagation conditions are very periodically at a twenty six to twenty eight day cycle, and that would be the rotation of the Sun's surface layers around its axis. C. What does the K index measure? It measures the short

term stability of the Earth's magnetic field. What does the ax A index measures? And it's the long term stability of the Earth's geomagnet field. Which of the following is typical of the lower hf frequencies during the summer, let's see high levels of atmospheric noise and static I think that that is correct. Okay, so let's let's talk about propagation some terms. There's a maximum usable frequency called MUFF. It's the highest frequency of which propagation exists between two points.

The lowest usable frequency l UF. Waves below the LUF will be completely absorbed by the ionis frequent by the ionosphere. MUFF and LUFF depend on specific data between two points, locations, and distance apart. It varies with the time of day, seasonal amount of solar radiation, and ionosphere stability. Operating near the maximum usual frequency often gives excellent results. Absorption is lowest just below it, one may One way to check

actual conditions is to listen for propagation beacons. Some provide real time propagation information. Many stations between twenty eight point one nine and twenty eight point two five megahertz that are excellent are excellent sources of information about ten meter propagation. To make contact with the distance station, you will have to use a frequency between LUF and MUF, so the wave has been back toward the Earth but isn't absorbed if the MUF drops below the LUF, then no propagation

exists between those two points via ordinary skywave. And there's on the on the web you can go find maps of the world that show the muff and the luff and it's got what the propagation is between different points on the Earth and the bands that are open, and a lot of good information out there. Okase talk about solar disturbances. Approximately eight minutes after a solar flare occurs on the Sun, the ultraviolet and X ray radiation released

by the flare reaches the Earth. This radiation causes increased ionization and radio wave absorption in the d region. A solar flare, which is a large eruption of energy and

solar mature. When magnetic field disruptions occur on the surface of the of a solar flare, there is a large eruption of energy and solar material when magnetic field disruptions occur on the surface of the Sun. A coronal hole, which is a weak area in the Sun's corona the outer layer through which plasma, ionized gas, and charged particles escape the Sun's magnetic field and streams away into space

at high velocities. A coronal mass ejection CME is an ejection of large amounts of material from the corona, and all of these disrupt HF propagation some sudden ionosphere disturbances UV and X ray radiation from a solar flare travels at the speed of light to impact the ionosphere about eight minutes later. When radiation hits the ionosphere, the level

of ionization increases rapidly, particularly in the D region. This increases absorption from causing a sudden ionospheric disturbance, also known as a radio blackout. Lower bands are more strongly affected, but communication may still be possible on a higher band. Sudden anospheric disturbances affect only the sunlit side of the Earth. The dark side communications may be relatively unaffected. Geomagnetic disturbances. This is the interaction between solar wind and geomagnetic field,

which creates a region of space called the magnetosphere. Charged particles from coronal poles and coronal mass ejections travel considerably slower and take longer to reach the Earth about fifteen to forty hours. These particles deposit their energy into Earth's geomagnetic field and increase ionization in the E region, causing oral displays and creating a geomagnetic storm, which affects higher

HF bands. First, long distance pass that traverse high latitudes, particularly those that pass near the magnetic poles, may be completely wiped out for days, for hours or days, and these can create auroras that reflect radio waves above twenty megahertz. Auroral propagation is strongest on six meters and two meters, modulating the signals with the hiss or buzz, so sometimes you can actually hear it on the signals. There's a modulation that happens. It's kind of cool effect. So here's

some questions. What effect does a sudden honest spirit disturbance have on the daytime iono spirit propagation b It disrupts signals on low frequencies more than those on higher frequencies. Approximately, how long does it take for increase ultra ultra violet X radiation from solar flares to reflect radio propagation on Earth?

About eight minutes? And what is a geomagnetic storm. It's a temporary disturbance in the Earth's geomagnetic field that bed How can a geomagnetic storm affect HF propagation It degrades high latitude HF propagation. How can geomagnetic activity benefit radio communications by creating a roar as that can reflect VHF signals. How long does it take a coronal mass ejection to affect radiopropagation on Earth? Usually it's about fourteen hours to

several days. It just depends. How is long distance radio communication usually affected by the charged particles that reach Earth from solar chronal holes HF communication is disturbed? What factors affect the muff? Just a maximum usable frequency, path distance, time of day, solar ardiation, all of those affected. Maximum usual frequency is which frequency will have at least have the least attenuation For long distance skip propagation, that would

be just below the maximum usable frequency. Once of the following is a way to determine current propagation on a desired ban from your station. Use a network of automated receiving stations on the Internet to see where your transmissions are and being received, because it's different all over the worth all over the world given at a given time, So check a network and see what the see what's

the receiving stations showing at a particularly given time. How does say honest sphere effect radio waves with frequencies below them up and above their gluffs. Yeah, they are refracted back to Earth. What usually happens to radio waves with frequencies below the LUF They are attenuated before reaching the destination so to get through. What does LOUFF stand for? It's the lowest usable frequency for communication between two specific points. Okay,

What does MUFF stand for? It's the maximum usable frequency between two points, right? And what does what happens to HF propagation when the luff exceeds the muff? Propagation is not possible over that path? That's correct, all right? Talk about some scatter modes, some terms called backscatter, that's reflections

from the from from features on the Earth's surface. Waves can also be scattered from within the IONO sphere, allowing signals to be heard from stations too distant to be heard by ground wave and on on frequencies too high for short for short hop skywave propagation, scatter and backscatter helped fill in the skip zone where signals would otherwise not be heard. Signals received via HF scatter are usually

weaker than those received by normal skyway propagation. Reflection is not very efficient and tends to spread out the signal. Such such signals sound disturbed, sound storted, resulting in fluttering or wavering. I'm striking the ground. After ionosphere reflection, radio waves may be reflected back towards the transmitting station. Backscatter consists of signals reflected by the ground back into the

skip zone. Backscatter supports communication between stations that would otherwise be in each other's be in each other's skip zone. So I've got a signal, I've got a h I've got a station transmitting here, and I've got another receiving station. He's out of my skip zone. But because of some backscatter, some of that is actually received by this particular station. So the skip distance he's too far, he's out of my skip zone. But scattered signals from the ionosphere, he

can sometimes hear me. And usually those are weak signals and they're fluttery, but he can. That's a that's a way he can. He can. I can communicate it near

vertical incident skywave in VIZ. We just talked about what's the INVIS, what what are How we can build an VIZ and invis antenna for signal below the critical frequency the ionosphere reflects waves arriving at the angle even vertical always above five megahertz up to forty meters in VIZ is for a signal below the critical frequency when it when it is radiated vertically, the reflected scatters the signal back to Earth through the region of up to two

hundred to three hundred miles. To make use of INVIZ, horizontally polarized dipoles are placed low to the ground so that the radiation pattern is almost omnidirectional and concentrated at high elevation angles near vertical incident skywave INVEZ communication and relies on signals below the critical frequency transmitted at high vertical angles. The signals are reflected by the aosphere back to Earth in the region around the transmitter. So here's

an example. I've got a transmitting station here. I've got a guy on the other side of this mountain. I can't talk to him directly, but I can bounce the signal off the iosphere and get to him. And you're using the F layer to do this. H transmit this these reflections. Hey, what's the effect of HF scattered? So was the characteristic of HF scattered? Uh? They have a fluttery sound. Uh, usually weaker signals. What makes HF scatter

signals often sound distorted? It's because there it's it's scattered to the zip code, the zip zone along several paths. Okay, Why are HF scattered signals in the skip zone usually weak? That's because only a small part of the signal is scattered back into the skip zone. What type of propagation allows signals to be heard in the transmitting station skip zone that would be scattered? What is a near vertical incident skywave propagation and that is short distance MF or

HF propagation using high elevation angles. Okay, our next section, we're going to talk about electrical safety, RF exposure and outdoor safety. So, first of all, talking about electrical safety, preventing electrical shock. Always have a master on off switch for station and workbench, clearly labeled and somewhat away from

the equipment. Don't put yourself in a position to be shocked when working inside equipment, Remove insulate or secure loose wires and cables, and use a ground stick to remove charge from capacitors. So, I see, what's a groundstick? Well, yeah, here we go. Here's a ground stick ground stick is a ground stick. It's touched to all circuitry inside an enclosure to ensure that that no high voltage is present.

The alligator clip is attached to an electrical ground and the eyebolt sput on a on a contact with the circuit So you've got an insulating piece of PBC pipe and this allows you to touch certain components and discharge them to the potential of the gap itself. So what's the effects of electrical current through the human body on an average person? Well below a millionamp generally you can't

perceive it. One million amp bank tingle, five million amps slight shock six to twenty five million ams painful for women, nine to thirty painful for men. Just the freezing you can't let that SIT's in the let go range fifty one hundred and fifty million amps very painful, and this is if you had contact. You know, inside the body, your skin is a resistance, so that helps, but it can be very painful. So it doesn't take much current to cause problems with the human body. Solder in safety

so primarily solder is primarily lead based. Ten is added to lower the melting point. Lead is a known toxin. Always solder in a well ventilated area. Rosin flux smoke is likely not good for you in high doses. Use a well ventilated area if you can. When finished, wash your hands, remove solder or flux residue. As of two thousand and six, environmental regulations were passed for solder to

eventually be lead free. Leaded soft are still available. Lead free sawder melts at significantly higher temperatures than traditional sixty to forty solder. Greater risk of damage to heat sensitive components because you got to you've got to run a little higher temperature. So what's the following is a danger for lead tin solder. Lead tin can contaminate food in your hands. Carefully, Hey, carefully, you know, wash your hands

after you've handled lead tin solder. Okay, Wiring practices National Electrical Code Handbook contains the details for handling AC wiring and the home in the station. Use your local building codes ensure that home is properly wired to meet special local conditions. You standard wire color conventions. Hot which is red or black insulation it's connected to the brass terminal, or screw neutral, which is white insulation is connected to

the silver terminal. Or screw, and green your ground. Ground is your green insulation or bare wires connected to the green or bear terminal screw. So those are the standard wiring AC wiring conventions use in your home. Don't run antenna feed lines overpower lines or service drops from a transformer to the house. Here's some standard wiring conventions. Standard wiring for outlets, one hundred and twenty and two hundred old AC plugs and receptacles. It's crrectally important to follow

the correct wiring techniques for AC wiring. The white wires neutral green wire is ground, and the red or black wire is the hot lead. Note that two hundred and forty volt circuits may have two hot wires and the ground, so be careful when you wiring things are hooking things up, observe the wire colors and the correct connections. AC wiring most common sizes are number twelve gauge for twenty amp

circuits and fourteen gauge for fifteen amp circuits. Use fuse or circuit breakers for the hot conductor for one hundred and twenty bolt circuits on both hot and use them on both for the hot conductors. On a two hundred and forty bolt circuit which uses the three or four wires. All right, here's the here's some current capacity ratings for some common wire sizes. The rating of a wire to

carry current is called this opacity. When you are finished wiring the job, verify that you have the connect correct connections by using an AC circuit tester. So make sure you follow the right proper wiring sizes for the right conductors, all right. Fuses and circuit breakers are used to interrupt excessive current flow. Fuses do so by melting a short length of metal. Circuit breakers act like a fuse, but trip when current overloads occur. Always use properly sized fuses

and circuit breakers. When installing fuses or circuit breakers in an AC circuit, be sure to replace them only with the correct ones, never in the in the correct lines, never in the neutral or ground lines. Be sure there's a fuse or circuit breaker in the hot conductor for one hundred and twenty bolt circuits and both conductors for two hundred and forty bolt circuit round fault interrupted circuit breakers are used in AC power circuits to prevent electrical

shock trips. It trips if unbalanced is since in currents carried by the hot and neutral conductors. Sensitivity is just a few million amps of a balance between the hot and neutral, well below the threshold for electrical injury safety interlocks. This is a switch that prevents dangerous voltages or intense RF from being present when a cabinet or enclosure is open. You'll see these a lot if you have a high power amplifier, especially two amplifiers. When you take the top off,

there's usually a switch that disables all the voltages. So if you're working on it and you know if you've got to bypass that, be real careful, all right. Several types physically disconnect high voltage RF when activated. Those are the switches I was just talking about. Usually take the chassis apart. There's usually a little rocker switch or some kind of switch in there that senses that shorts or ground high bolted circuits when activated, possibly blowing a circuit

breaker or fuse, and the power supplies. Which wire wires in a four conductor to forty vowl AC circuit should be attached to fuses or circuit breakers? Okay, only the hot wires A you should not fuse The ground or circuit should not fuse The ground wires according to the Natural Electric Safety Code. What is the minimum wire size that may be used safely for it twenty amp circuit? That would be the twelve gate wire. What size a fuse or circuit breaker would be appropriate to use a

circuit that uses a twenty A fourteen gauge wire. That would be the fifteen amp circuit breaker. Which of the following conditions may cause a ground false circuit interrupted? To disconnect AC power current flowing and one or more of the hot wires and the neutral or the hot wires to ground over voltage of the wires. It would be current flowing from one or more of the hot wires directly to the ground. B Which of the following is covered by the National Electric Code? That would be the

electrical safety of the station. What is the purpose of a power supply interlock? Let's see it would be to ensure dangerous voltage or mirder moved from the cabinet when it's opened. That would be c okay. Some generals, some generator safety, fueling and ventilation problems cause more injuries associated with generators than from any other cause. Install generators outdoors, use them outdoors, Carbon monoxide and exhaust and quickly build

up to toxic levels. We're using generators regularly. Installs carbon diox carbon monoxide detector alarms in living and working areas. Generator output connected directly to the homes. Wiring system must have the ability to disconnect power service from utility lines. Generators should always be shut off when refueling to avoid igniting fumes or splashing liquids from the spark flobe. A fire extinguishers should be kept near the generator and separated

from the fuel. Here's some practice questions. Which of the following is true of an emergency generator installation. Generator should be operating, well operated and it's insulated from ground. It would be a should be operated in a well ventilated area. Lighting lightning goals of lightning protection. You should provide fire prevention for your home. It should it reduces or prevents electrical damage to your equipment. Use metal heavy use metal

entry panels where signal control cables entered the house. Panels should be grounded nearby with a heavy metal strap. Ground rod must be bonded to the AC service entry ground rod outside the building with the heavy conductor and lightning arrestors should be installed at the entry panel where the feed line enters grounding wires and straps should be as short and directly and direct as possible. Do not use solder or to make ground connect ground connections. Solder joints

could melt if hit by lightning size current. Use medical clamps, braising or whaling so you know. Never use a solder connection for your Whever you use solder to make ground connections, where you can have lightning compete, All towers, mass and antennas should be grounded. What should Why should solder joints not be used in lightning protections because a solder lightning

will likely be destroyed by the heat of lightning. A. Where should the station's lighting lightning protection ground system be located? It should be outside the building of force. Which of the following is required for lightning protection? Ground rods lightning al must be connected d They all must be bombed together with all other grounds. Where should lightning arrestors be located? Where where it enters the building? They are exposure at

high power levels. For some frequencies, the amount of energy that the body absorbs can be a problem. The maximum permissible expose your MPE is maximum intensity is the maximum intensity of r radiation to which a human being can be maybe exposed. Factor to consider when estimating MPE, that is, transmitter power level, density, frequency, average exposure time, and duty cycle of the transmission. Power density and frequency are primary ones.

Those are things that you should think about. How much power you putting out? What's your frequency? What's your exposure time? In the duty sizet. Stations with a time average transmission of more than one milli a lot are subject to the FCC's ARF exposure rules. If your station exceeds the exemption criteria, you will need to evaluate it and according to the FCC OEt bulletin sixty five, So what does

that mean? So talk about that in a minute. Power density is heating from exposure to RF signals caused by the body tissue absorption of r F energy, measured in milliwats per centimeter squared. R F field strings can also be measured in volts per meter and amps frem or milliwatts centimeter squared is the most useful for amateur requirements.

Power density is highest near antennas and in the directions of which antennas have the highest gain, decreasing transmitter to power and increasing distance from the antenna lowers power density and vice versa absorption and limits SAR, which is specific absorption rate. This is the rate at which energy is absorbed from the is energy absorbed from the power to which the body is is exposed. It's best the best

measure of ARF exposure, but it's difficult to measure. SAR varies with the frequency, power density, average amount of exposure, and duty of cycle of transmission. SAR depends on frequency and size of the body or body part affected. Highest where the body or body parts are naturally resonant. Safe levels of STAR based on are based on demonstrated hazards have been established by the FCC in the form of

maximum permissible exposure limits or the MPE levels. Maximum permissible exposure MP limits vary with frequency because the body responds differently to energy at different frequencies. The controlled and uncontrolled limits refer to the environment in which people are exposed to the r F energy be taken into account the variation of the body sensitivities to r F energy at different frequencies. So you can see here that based on the frequency, the power density levels in a controlled and

uncontrolled environment UH at different frequencies. So in this particular case, the this is where the body is more most sensitive to RF radiation mm HM. The limits of occupational controlled exposure UH. These are the you've got frequency range, the power density UH controlled environment in the in the uncontrolled environment ranges, controlled exposures limits supplies to control. The controlled exposure limits apply to individuals trained in r F exposures,

such as the licensed amateurs. Uncontrolled environment is is those who is the general publics and their levels are just a different level, are just a different are are just a little higher. UH. The uncontrolled exposure limits apply to individuals not trained in r F exposure, so the general

public UH. And you'll notice here. So so these are the frequency ranges and their exposure levels and the average time you you're required as an UH, you're required to do a UH UH an exposure analysis for your station. There's an r F calculator at the A at the a dobr L that allows you to put in some of these things here, such as such as UH transmitting frequency, antenna gain, and it will calculate the safe distance based

on the exposure levels that you need to maintain. Okay, the things that control the duty, the things that are The things that control duty cycle UH and the uncontrolled environment are exposure RF energy, which is average over fixed time intervals. Time averaging evaluates a total RF exposure over a fixed time in two types of averaging periods are

controlled and uncontrolled. The controlled is where you're aware of your exposure and are expected to take reasonable steps to minimize in controlled environment examples transmitting the controlled environment examples transmitting facilities near antennas. Uncontrolled environments are like general public asset our general public access. People in an uncontrolled environment are not aware of their exposure but are much likely

to receive continuous exposure. Sure duty cycle is a ratio of the time the transmitter is on to the total time during the exposure. Maximum is one hundred percent, same as duty factor, but duty factor is expressed as a fraction. A lower transmission duty cycle permits greater short term exposure levels for a given average exposure. The less time the transmitter is on, the lower the average exposure, permitting greater

short term exposure levels for a given average exposure. Along with operational duty cycle, the different modes themselves have different emission duty cycles. Operating duty factors of modes commonly used by amateurs. For most amateurs, operating listening and transmitting time are about the same, So duty cycle is rare really

higher than fifty percent. Right. Calculating the average duty cycle power a station is using single side band without speech processing, transmitting listening for equal amounts of time and with transmitted power one hundred and fifty watch calculating the average outfoot power. Average duties power cycle is equal to the transmitted power times the emission duty cycle times of operating duty cycle.

So if you've got a transmitting power of one hundred and fifty wats and uh, and you've got a duty cycle for about twenty percent processing operating fifty percent of the time, then your average duty cycle power to be one hundred and fifty wats times twenty times fifty percent about fifteen watts. Let's see's back up at a section again here. Yeah, guys are talking. I know you guys are talking, but it's kind of affected me a little bit. No, no, no,

it's okay. I just want to just redo a section talking about we're going to go back to uh figure I mean, I mean you guys. Uh. Let's go back starting with RF exposure section nine point two slide thirty two. Okay, okay, so I'm going to start here and you got I know, you got to talk, but if it's sort of contract me a little bit. And I was okay, yeah, yeah, I just figured let me go back and do that section again. Okay, is this the last section? Yeah, this

is the last thing. We're thirty two sixty four at thirty two slides left and we're done. Ok But I was more reading. I was getting a little it didn't sound too good what I was doing. So yeah, well that's up. Let me look at this see if you got enough, if you got enough time, find you got thirty six minutes levels. Okay, I think I can do that. Yeah, so you all be on the same file. Yeah, okay, so we're going to start RF exposure again. Okay, okay, so you can find this chart and sorry about that.

I just want to make sure I just sounded pretty good. Okay, we're going to talk about our exposure. This has to do at at high power levels. For some frequencies, the amount of energy that the body absorbs can be a problem. Uh, there's a maximum permissible exposure called MPE, and that's the maximum intensity of r IF radiation to which a human

being can be exposed. Factors to consider when calculating your MPE are transmit power level or density, the frequency, the average exposure time, and the duty cycle of the transmission, which is power density and frequency are the primary ones here. Stations with a time average transmission of more than one milliwat are subject to the FCC's r IF exposure rules. If your station exceeded the exemption criteria, you will need to evaluate it according to the FCC, and it has

an OEt bullet in sixty five. The ABRIL has a online calculator where you can go calculate what the RF exposure is or how what's the minimum distance someone needs to be from your transmitting and transmitting antennum. And we're going to talk about there's two environments. We'll talk about power density first. U power density is heating from exposure to RF signals is caused by the body tissues absorbing r F energy. It's measured in wats per milliwats per

centimeter square. R F field strengths can also be measured in volt super meter or amps per meter, but milli wats per meter centimeter squared is the most useful for amateur requirements. The power density is highest near your transmitting antennas and the directions of which the antennants have the most gained. Decreasing the transmitting power that the transmitter power and increasing the distance from the antenna will lower the

power density, and vice and vice versa. The absorption in limits, there's a unit called SAR, which is a specific absorption rate. Is the rate at which energy is absorbed from the power from from power to which the body is exposed. It's it's the best to measure you are if exposure, but it's sometimes it's best to measure, but sometimes it's difficult to go back to actually do it. And it varies from with frequency, power density, average amount of exposure,

and duty cycle. All those are factors that come into the SAR. The SAR measurement and also depends on the frequency and size of the body and the body part affected. UH It's it's highest where the body and the body parts are naturally resonant. Safe levels of SAR are based on demonstrated hazards and have been established by the FCC in the form of maximum permissional exposure limits. So they've taken all this to effect and they've come up with the thing called the mp ees. M p E is

the maximum PERMISSIONBLE exposure. And these limits vary with frequency and UH. And they've they've come out and characterized the the the MPE based on frequency and power densities. And this chart here shows that. And there's two levels. There's a controlled environment in an uncontrolled environment. The controlled environment is where UH. The controlled environment is is is where the people are are aware of the are aware of r F and UH usually controlled by m can be

controlled by UH access. Let's see, I'm gonna do this chart again. Okay, we're doing yeah, you and milling them with respact to get up, doctor. That's okay, okay. Maximum permissible exposure or MP limits vary with frequency because the body responds differently to energy at different at different frequencies. The controlled and uncontrolled limits refer to the environment in which people are exposed to the r IF energy. These take into account the variations in the body's sensitivity to

r F energy at different frequencies. The limits for occupation and controlled exposure are shown here. The controlled exposure limits apply to individuals trained in RF exposure, such as licensed amateurs. Uncontrolled exposure limits applied to individuals not trained in RF exposure, so usually that's the general public. Okay. Exposure of r F energy is averaged over fixed time intervals. Time averaging evaluates that the total r F exposure over a fixed

time energy two types of averaging periods. There's the controlled and the uncontrolled. And the controlled averaging you're aware of your exposure and are expected to take reasonable steps to minimize Controlled environment examples include transmitting facilities near antennas. An uncontrolled environment would be like public access. People are in an uncontrolled environment are not aware of their exposure, but

are much less likely to receive continuous exposure. Duty cycle is the ratio of the time the transmitter is on to the total time during exposure. Duty cycle is expressed in a fraction instead of twenty five percent, So a lower transmission duty cycle permits greater short term exposure levels for a given average exposure. Called operational duty cycle, the less time the transmitter is on, the lower the average exposure, permitting greater short term exposure levels for a given average exposure.

So along with operational duty cycle, the different modes themselves have different emission duty cycles. Twenty to forty percent duty cycle if you're doing a single side van with AFSK or slow scan TV, that's one hundred percent single side excuse me, and voice amplitude like AM modulation is fifty percent twenty one hundred percent. AM modulation is twenty five percent duty cycle FM voice one hundred percent duty cycle

digital FM one hundred percent. So that all the digital modes that we use that we talked about are one hundred percent duty cycle modes like j like JTA. When your transmitters on is we consider it's one hundred percent duty cycle. Okay. Calculating the average duty cycle a station. If a station is using single side van without speech processing, transmitting and listening for equal amounts of time, and when transmitting power of one hundred and fifty watts, how how

would we calculate that average power output? So the average duty cycle power is the transmitted power times the emission

duty cycle at times of operating duty cycle. So in this particular case, we've got one hundred and fifty watts, where we've got an emission duty cycle for single sideband about twenty percent, and are operating duty cycle is fifty percent, So our average duty cycle power I got one hundred and fifty watts, but on times twenty percent of my mission duty cycle times transmitting fifty percent of the time,

I get fifteen watts if you want to. If you all fixed ameateur stations must evaluate their capability to cause RF exposure no matter whether they are using high or low power. Limits vary with frequency and PEP. You're required to perform the evaluation that your power exceeds the level

shown for any band. The r IF exposure evaluation is limited by three different methods during r F field strength with calibrated meters UH using the computer or model calculating to calculate your exposure or the easiest way is to use the a double r l's online calculator for r F exposure. So what you need to do to use the exposure calculator is what's the power of your antenna including adjustments for feed for for a duty cycle and feed line loss. UH. You got to know your antenna gain,

your high above ground, and you're operating frequency. And when you have those items, UH, you can go use the exposure calculator to figure out, UH what the exposure is around your antenna system. When when when you UH, what what I've done for my home is I've got I know what antennas I have, I know what operating modes I use, and I go run that calculation through that

a double r L calculator. I print those out and I've got those at my station, so I know uh how far or how close uh people can can can be to my systems. And for my home use, I'm in pretty good shape. I've got an unfenced backyard. But at the my my worst case is like ten feet from the end from from the end from the antenna, and all my intentors are ten feet above the ground. So my my RF exposure analysis shows on them in

pretty good shape. Whenever I go to a public service event, if we're out in the public like a field day, you should go to an exposure analysis of the antenna's that you're going to be used. And you should. And if you've gotten an area where the public can get close to antennas, then you're gonna have to use some barriers to market offer to keep people away. Okay, so here's some good practices for RF exposure. You know, locate and move antennas away from where people can be exposed

to excessive r F fields. Locate the antenna's a away from property lines and place fencils around the base of the ground mounted antennas. Don't point gain antennas where people are likely to be. Use beam antennas to direct RF energy away from the people. When using stealth, addict or indoor antennas. Make sure your MP limits are not exceeded in your living quarters. VHF and UHF. Place mobile antennas on a roof or trunk of a car to maximize

shielding of fasseters. Use dummy load or dummy antennas when testing a transmitter, and of course, reduce the power and duty cycle of your transmissions. Yeah, here's some questions. What's one of the ways that RF exposure can affect human body tissues? It can heat up the body tissue. That's what ARF exposure do is you can feel it as heat. You'll hear people talk about RF burns. Which of the following is used to determine ARF exposure from a transmitting signal,

power density, duty cycle? All of these are correct. All those affect how much your R exposure. How can you determine that your station complies with FCC RF exposure regulations? You can calculate it using the FCC OEt bulletin Computer modeling using fill screen. All those are are ways in which you can measure your compliance with RF exposure. What does time averaging mean when evaluating RF radiation exposure? See average amount of time powers applied by the transmitter average time.

It's a total time. It's a total RF exposure over a certain period. It would be d What must you do if an evaluation of your station shows that the artific energy radiated by your station exceeds permissible limits for possible human absorption, take action to prevent exposure to the fields? Filing it impact FCC Secure written permissions. It would be a take action to prevent human exposure in the excessive r F fields. What must you do if your station

fails to meet the FCC RF exposure exemption criteria? All right, so what must you do if your station fails to meet the FCC RF exposure criteria? So what you want to do is a perform an RF exposure evaluation according to those bulletins. Okay, what is the effect of modulation duty cycle on RF exposure? The higher the duty cycle creates let's see, ye, the higher the duty cycle from its greater power levels to be transmitted. That makes sense.

The more your transmitters on, the higher the RF exposure will be. Which of the following steps must an amateur operator take to ensure compliance with FCC regulations. Let's see POST a copy performer. Yeah, it's going to be C performer. Routine art exposure valuation to prevent access to any identified high exposure areas. Okay? And what type of instrument can be used to actually measure r F field strength? Let's see BB a calibrated field strength leader with a calibrated antenna.

What should be done if evaluation shows that a neighbor might experience more than the allowable RF limit exposure from the main lobe of a directional antenna? You can change the antenna height game use an antenna with the higher front the bank. Take precaution to ensure b C. Take precautions ensure that your antenna cannot be pomed in the direction when they are present. Okay, what precaution should you take if you install an outdoor transmitting antenna b C.

Make sure the MPE limits are not exceeded in occupied areas. Okay. What stations are subject to FCC rules on RF exposure? That would be d all stations with the time average transmission of more than one mili a lot. Okay, talk a little bit about it. Outdoor safety installing antennas, make sure you place all antennas and feed lines well clear of power lines. No part of an antenna system should

be closer than ten feet from power lines. When working on roofs, trees, or towers, climbers, helpers should wear appropriate protective gear at all times. Run through a safety check list every time, turn off and unplugged all AC equipment, locking circuits out and tagging them if possible. Transmitters should be off and it's connected from feed lines to avoid shock or excessive arf exposure. Belts and harnesses must be written, must be within their service life and attically rated for

the weight. Of course, check check the weather report, and of course take your time. Here's some practice questions. Which of these choices should be observed when climbing a tower using a safety harness. Confirm that the harness is ready for the weight of the climber and that is within its allowable service life. Be done Before climbing a tower that supports electrically powered devices, You should be make sure all circuits that supply powers to the tower are locked

and tagged out. Are locked out and tagged