TechStuff Goes Transmitter Hunting - Part Two

transmitter hunting. Our our friend, my coworker, Joe McCormick joins us to talk about this interesting use of technology and how it's been turned into a sporting event, something that you can participate in if you have the desire, So let us rejoin the show. We need to move into more of a discussion about radio specifically, because even though radio is a subset of electromagnetic radiation, it covers an enormous range of frequencies and therefore wavelength and not all

frequencies behave the same on Earth. True. Yeah, so you've got different bands you might have You've seen terms like HF for VHF you HF. These are specific sub bands of frequencies on the electromagnetic spectrum, all what we would call radio frequencies. But um, so yeah, you've got like high frequency, very high frequency, and a lot of what we're gonna be talking about today is going to be in the VHF part of the spectrum, that very high frequency.

So yeah, this radio spectrum is pretty broad, and it goes well beyond the types of radio that that the typical person can listen into, unless you happen to be one of those folks who you know, maybe you operate a maritime radio to help with navigation, in which case

you are using frequencies most of us don't touch. But or maybe you're are a doctor working with experimental medical imaging equipment, in which case you're using radio frequencies on the opposite end of the spectrum, because maritime radio uses very low frequency UH radio waves, whereas medical imaging uses

extremely high frequency radio waves. So the range goes from the bottom is at like three hurts, which means you get three waves passing a given point in a second, all the way up to tremendously high frequency, which is three thousand giga hurts or three trillion hurts, meaning three trillion waves pass a given point within a second. Actually like extremely low frequency. More because the acronym is elf so elves, elves communicate kind of like nts, very long

wave forms. The elves at the bottom of the ocean yeah, that's where we've stuck them. So again, you know, we talked about how all these waves are traveling at the speed of light, so it's really just the number of waves that pass a given point in a second that tells you a frequency, not speed of transmission, because that's going to remain the same no matter what. So, um, a three hurts frequency wave, we'll tell you that the wave length or that particular wave has to be a

one hundred thousand kilometers in length. That's a long radio wave hundred thousand kilometers. Meanwhile, in the opposite ind of the spectrum, if you go all the way to that three thousand giga Hurts wave, you're talking about a hundred micrometers in length. So teeny tiny micrometers are very tiny, huge difference obviously in the length of these waves. Um. So that's why you know, the whole frequency wavelength relationship is important. So we use the different frequencies for very

specific purposes. It's also important to point out that this is not universal. The There are usually some sort of governing body within a country that designates what frequencies can be used for what purposes. In the US, we have the FCC, uh, so if you're looking at the terror hurt side of things, that's that ultra ultra high or terribly high frequency as is some sometimes referred to. It's for medical imaging, that that kind of stuff also molecular

dynamics measurements and other high tech information. Uh. The extremely low frequency would be like radio communication with submarines. You can't you can't use very high frequency when communicating with stuff that's underwater. The waves attenue are the radio waves get attenuated by the ocean water, and that creates problems with communication. But it's less of a problem with with

extremely low frequency and very long wavelength radio transmissions. What about the kind of radio we think of as standard radio, as in radio accessible to the average consumer AM FM, That kind of stuff, so AM would be in the medium frequency. Medium frequency ranges from three killer hurts to

three thousand kill hurts or three mega hurts. If you prefer AM radio specifically in the United States is in a even more narrow range than that, right, that's all of medium frequency AM radio in the US goes from five killer hurts to one thousand, seven hundred kill hurts or one point seven mega hurts. UM if you wanted to talk about shortwave radio. That's from five point nine

mega hurts to twenty six point one Mega hurts. CB goes to twenty six point nine six mega hurts to twenty seven point for one mega hurts, and so on and so far. So so FM radio is gonna be that's mega hurts, right, So it's going to be around around MEA hurts exactly. So yeah, because power nine and nine that would be at ninety nine mega hurts right one I think originally maybe high thing, yeah, and goes

up to like one oh seven I think somewhere around there. So, uh, Different countries of allocad their broad broadcast spectrum in different ways, so not everyone follows those exact same rules. There's usually some overlap. Um. Now, when you know something about the wavelength of the radio frequency, that tells you what you need how you need to build your antenna right, Because the length of your antenna is dependent upon the frequencies

you're looking for. You want your antenna to be the right length to resonate properly with the radio frequencies you're searching for. And there's no such thing as really a perfect universal antenna that can equally pick up all frequencies across the radio range. Now you might wonder, how can you have like a pocket AM radio, because if AM radio is broadcasting in the medium frequency and has pretty long radio waves, and you need to have an antenna

that is the right length to pick that up. Typically we're talking about half the length of the wavelength of the radio frequency you're looking at right, So if you're talking about like a a wavelength that's a hundred meters long, then you're looking at our radio antenna that's between forty and fifty meters. How the heck do you fit that on like that? That seems ridiculous. Well, the antenna for a M radios are typically wire that are UH and

that wire is wrapped around the core. Because it doesn't matter if the wires straight or not straight or whatever. You can you can coil it inside a device and have it completely housed within the radio. So if you were to open up an AM radio, chances are you'd find a wire where one end is not attached to anything and it's just wrapped around around around around around a core of some sort. That's the antenna. It's it's

not like it's providing any sort of electrical uh. Stimulation apart from conver you know, pulling in radio waves and having that induce an electric current. So, uh, that's why AM radios don't necessarily have a visible, incredibly long antenna um. And this is important when it comes to things like

transmitter hunting. Yeah, because if you look at transmitter hunting sites and we'll get into the specifics of the sport here in a minute, you see a lot of jargon that obviously has to do with stuff about like antenna length and frequencies and stuff like that. One of the common things you'll see is like the idea of a two M hunt. The the the two M arena is

often considered the sweet spot for for transmitter hunting. Now, what does that mean When a HAM radio enthusiast talks about two meters and they're telling you specifically about the size of the antenna that they are using. The two meters is a pretty decent sized antenna, right, like you know, a meters. Like here in the United States, we don't necessarily think in terms of meters that frequently because we're

not on the metric system. But yeah, that's the reason is because the frequencies that are being used by HAM radio enthusiasts are falling in the VHF radio frequency band, that very high frequency. Now, that frequency band goes from thirty mega hurts to three hundred mega hurts, and the radio wavelengths go from ten meters down to one meter. And we're using descending sizes because remember as frequency increases,

the wavelength decreases. Right, So if you if you're hunting for a radio signal that's somewhere and that uh, that four to five meter range, you need a two meter antenna in order to pick them up effectively to to have it be particularly sensitive to those transmissions. Now, the specific range within VHF designated for amateur radio use is in the United States a hundred forty four mega hurts

two hundred forty eight mega hurts. It's a little different than Europe where it's one forty four to one forty six and not quite as wide a range. Give us our two mega hurts. Come on, yeah, and well, to be fair though, it's not the only band for amateur radio. Amateur radio actually has bands and several different frequency ranges. It's just for the VHF frequency range. It's this specific range of frequencies from in the US six in Europe um.

But you can also find amateur radio frequency bands in low, medium, and high frequency as well as all the way up to like terribly fast terribly high frequency. You can find them up there too. Now because of the wavelengths involved, that two meter antenna is best able to pick up those transmissions because it resonates more readily with transmissions in that frequency, Like it can pick up stuff outside of it, but not as effectively as the stuff it was designed for.

It's that's the sweet spot. So you can build your own if you want to do. There are a lot of different resources, both online and in libraries that will teach you how to build an antenna. I watched one that actually was so cool that I think I might do it as a project here and how stuff works and do a video about it. What kind of antenna was it would be? It would be a quad antenna, but I'll talk about a little bit a little bit later. Mostly because I've been thinking about trying to build a

Yachi antenna. Yeah, well that would be great, some of them, as some of the Hams pronounced it, yagg Yeah. I think that that project would be really kind of fun, and also I like the way a quad antenna can look. I'll talk more about that in a little bit. Anyway, well, I will I challenge you to an antenna build off. That sounds great, Yeah, let's do it solely. Do it to be fair, It's way easier to do it now than it was in the old hobbyist days where you

had to do all the calculations by hand. Now there are so many online tools that will allow you to just plug in what you're what you're attempting to do, and he'll tell you exactly how long each element. I've been to exactly one of these calculators. I found one online that says like, Okay, here's the frequency I want to look for, here's the decibel gain I want um, and then it will tell you the relative size of

your of your elements for your antenna. Yeah. So, if you are a transmitter hunter, chances are you have multiple antenna or as I put, a veritable array of antenna perhaps a literal array of antenna's, depending upon what you're you're depending upon how much in time you have to put into the hobby. But then we also have another

element that that you put in our notes a question. Yeah, so sometimes you'll hear or you'll read about people in the transmitter hunting community talking about harmonics, you know, so they'll say, maybe, oh, I got very close to the transmitter and I was I was overwhelmed. What could I do? You know, I I suddenly I couldn't isolate the direction of the signal anymore. And somebody else might say, well,

try looking for the third harmonic. I love that because it sounds very cryptic, and in the know it sounds a little Star Trek esque in a way. So harmonics are into drum multiples of the fundamental frequency, which is a fancy way of saying you start with whatever frequency you're looking for, because generally speaking, transmitter hunters there's a specific frequency that they know they are searching for, otherwise

it would be needle in a haystack, right. Plus they're limited anyway by the range that amateur operators are allowed to use. So you start with whatever the target frequency is and you multiply it by integers in order to get the harmonic. So the first harmonic is the fundamental frequency because you just multiplied by one, got it. So third harmonic you multiply by three, fifth harmonic you multiply by five. Both of those are particularly useful in transmitter hunting.

So the typical frequency you'd be hunting for is one forty six point five six five mega hurts. Now, if you want to find the third harmonic, you multiply that number by three. That gives you four d thirty nine point six nine five mega hurts. The fifth harmonic you multiplied by five. That gets you seven two point eight to five mega hurts. Now, each of those harmonics has a weaker signal than the fundamental frequency, but it would be related to the fundamental It is related to it,

but it is a weaker signal. Now, if you're when you get close to one of these transmitters, chances are the signal strength as such that you are it's hard for you to get any useful information right, Like you might if you have a directional antenna, which we'll talk about in a minute, you might be sweeping it all around and you're just maxing out your receiver no matter what direction you pointed in right because the signal it's not like you're right on top of the transmitter, but

you're close enough where the directionality is no longer useful. It's kind of like you can hear someone yelling off in the distance and you're blindfolded, so you know generally what direction they're in, But as you get really close and they're yelling and it's an echoe area, you can't really tell where the noise is coming from necessarily. It's

kind of like that as an analogy. So if you're able to switch to one of these harmonics because it's a weaker signal, you can get a little more precise with that directionality you can use if you have an antenna that can switch to one of these signals, or you have an antenna specifically made to detect those harmon necks, then you are able to switch to a weaker signal which is not going to overwhelm your antenna so quickly, and you can hone in on the direction a little

more precisely than you would if you had to rely on your your chief two meter antenna. Right. So that's why harmonics are important. Uh, and we well, we'll talk a little bit more about the Yaggy antenna's in a second. Yaggy antenna more formally is the Yogi Uda antenna, which sounds like it should be a Star Wars character. Right, Oh,

you seek yagi Uda. It's a directional antenna that looks kind of like one of those old TV antenna's, like the old arials that you would see on top of houses, typically in the movie like Uh Willy Wonka and the Chocolate Factory. Yeah, it has It has one long boom in the middle as well for two a central poll on which are mounted parallel elements. These elements are does the shaping and receiving of the signal or transmitting. You can have a transmitter or receiver. Sure, yeah, antenna they're

meant to be both transmitters and receivers, right. Typically the antenna that that I use and most people use, I would imagine are simply used as receivers, except when you get into things like phones and stuff. Obviously, any any phone type device has both a transmitter and a receiver. Otherwise it's just a radio, so not terribly useful if you want to make a call. Anyone does anymore, But

I digress. Well, anyway, we'll talk about the specific sent a minute, but the the point of these parallel elements on the Augie antenna is to create this directional effect where a signal is detected if you are pointing right at it, but it is killed if you are pointing perpendicular to it right right. So the idea being that if you turn to your right and the signal suddenly drops out, you know that the direction to the right is not the way to go used to turning to

the left. And you find where the signal drops out, you can eliminate that. It narrows down the range where the transmission can actually originate. And since transmitter hunting is all about finding that transmitter, that's important. And we're gonna talk more about transmitter hunting and really dive into the hobby and the sport in just a moment. But first

let's take another quick break to thank our sponsor. Alright, we're back, and Joe, I want you to tell me more about this sport of transmitter hunting, a sport I did not know existed until you brought this topic to my attention. Uh. Yeah, so I at some point I want to try this. I've never done it myself, but I've been reading about it over the past couple of months, and I've watched a few videos of people trying it out on you tube, um, and it looks very interesting.

So the sport is known as transmitter hunting also t hunting or fox hunting. UH, And a standard game goes like this. You've got one participant who is the hider. This is sort of the dungeon master of the fox hunt, and the hider puts together a radio transmitter appropriate for the scale of the hunt. So you might use a small handheld transmitter stashed inside an old ammunition can for a small scale hunt on foot or in a you know,

small several mile mile area with cars. And in this scenario, you would set the transmitter to repeat a signal at steady intervals, so it might be like BP beep, bpit beep, beep, and then you hide it somewhere, maybe in a public park or another reasonably small search area. For large scale hunts, you can actually build a powerful antenna capable of insmitting

miles and miles across state lines. There are people who do this in you know, these long all day car hunts where they're going a really long way to try to find a transmitter somewhere out in the desert or something. It looks like a lot of fun, and you use it. You hunt it using cars or maybe fan boats, you know, so you can you can do this in the Everglades. I would that's just the way I would like to do it. I just all I can imagine is now we we talked earlier about possibly making a movie that

this movie would now have to star Bert Reynolds. But if you are hiding a transmitter, there are some social and safety concerns you probably want to keep in mind. Makes sense. Imagine, for example, you are out at a public park with your children and you see some creepy loaner with an antenna attached to their van pull up beside the park and then put a bunch of electronics inside an ammunition can and hide it in the bushes next to the sandbox. I would say that would raise

at least one, possibly two red flags. Right, So you probably first of all, need to be careful where you hide your transmitters. You need to uh, if it's you know, in a place where you would need permission, get permission first.

In any case, if you're doing transmitter hunting, I've I've heard that it is a good idea to notify the police ahead of time that they're going to be people running around with antenna's and that you're gonna be hiding a thing and let let the police know where you're hiding it so that it doesn't get mistaken for a bomb or some other nefarious device. Yeah, it also looks like it's a good idea to put some writing on the device warning people that it's not dangerous, although honestly

you wouldn't believe it. Yeah. I mean like if I were, if I were the type to make a device that was intended to be harmful to people, I can't imagine that I would have the ethics to avoid writing this totally will not harm you. It's like, I'm pretty sure a box of hot pocket says this is not dangerous on it. Yeah, I mean it all but but but definitely go to that extra effort. Lah. We we were talking offline about this before we came in here to record the episode, and the world is a very different

place than what it was when. Uh. Transmitter hunting was really one of those hobbies that that that people could essentially go anywhere and play. No one really noticed because they didn't even It was just beneath the public consciousness.

Joe found a book and lent it to me that I got to read, and in it they describe a situation where one person who was hiding a transmitter didn't have the time to actually do it himself, and so entrusted the transmitter to two other people who said, oh, yeah, we'll totally hide it where you told us, and instead they went and hit it under an overpass. And I thought those days are over. You would get into so much trouble now because you were hilarious prank back then.

Now freaks people out. Yeah, you remember the Moon and Knights. Those are characters from Aquitine Hunger Force, where they they Cartoon Network had done this promotional stunt where they put very simple led displays of the moonaites over certain bridges, and it freaked people out. They thought perhaps it was like a weird warning about an explosive that had been attached to said overpasses. Turned out, of course, no, it was just a promotional stunt, but no one knew that

at the time. And in the world that we live in today, it's probably better to take those extra precautions and to uh to let whatever authority oversees the area that you're planting the transmitter in to know about it ahead of time, get approval that kind of thing, and take these extra steps to make sure you don't inside a panic. By the way, you mentioned this book, and I just wanted to throughout the name of it because as I was looking at this too. It's a book

I order called Transmitter Hunting Radio Direction Finding Simplified. It's from the late nineteen eighties and it is a radio hobbyest manual by Joseph Moel and Thomas in Curly. An exhaustive hobbyist manual. Well, they've got a lot of projects and stuff back then for building different antenna types, but also just sort of an overview of what the sport

looks like, you know when people practice it. Uh So, when you when you get into a transmitter hunt, you've got the transmitter hidden somewhere and you've got some boundaries established, and then the players are set loose. They're like the dogs on a fox hunt, which I assume is where the name comes from and not some other counterintuitive naming scheme. Uh. But they know what to listen for, so they've got the frequency established, they know what the signal is, but

they've got to somehow find the physical location of the transmitter. Uh. Now, once you think you have isolated the direction from which the signal is coming, and in just a second, we'll talk about ways you could do that, some different equipment you could have, but typically you'll have some kind of antennae or device that gets you a bearing. So you've got a line to where you think that the signal is coming from, and then from there. There are a couple of primary ways you can hunt. One is the

simple way, which is just chasing the bearing. Even this is not as simple as it sounds. It is that you found you found a direction and you're like, okay, well the transmission is coming from the southeast, so let's just get in the car and travel as close to southeast as we possibly can for a while, and then we'll jump out and check again. Yeah, so you just follow it and then keep checking the signal. The other

way would be what's known as triangulation. And so there imagine you would need a map for this, an actual physical paper map would probably you can make marks on as accurate distances and measurements. Uh. So you get a bearing from one known location, You know where you are, You mark your location on the map, and then you get a bearing. So you draw a line on the

map saying okay, it's coming from this direction. You go to another place on the map and you mark your location there, you get a bearing again, you say, okay, it's coming from this direction. Draw another line. Then you go to a third place, get a bearing again, and maybe do that another time. So, if everything is working correctly, those three or more lines should begin to intersect the location of the transmitter. There should be a convergence around

the general area. Now, it may be because of geography and buildings and such that the signal you're picking up is a reflected signal and not not really indicative of the actual source of transmission. Right, Like, let's say that the source of the transmission is off by a few

degrees from where you get your bearing because of this reflection. Well, as you do your triangulation, you might notice that that the this intersection is a little weird, like not all the it's not like all the lines are converging on a single point. It might be that they create a

trapezoid of possibility. And then the idea is that, all right, well, now we're gonna need to get further closer to that trapezoid because we know that the transmitter is most likely within that area somewhere, but we have to narrow it down from there. Either way you go, if you're just homing in on a bearing or if you're trying to

do triangulation. It's not as easy as it sounds, because, as you alluded to, the propagation of radio waves can be affected by all kinds of stuff, many variables like terrain, uh presence of water, reflective obstacles like fences, power lines, or even concrete buildings. So a hill can block your line of sight to a transmitter. Yes, so if the hill a hill can be in the way, you might jump out of your vehicle and you're trying to pick up the signal and you can't pick up anything or

or whatever. You so weak that you can't really get a reading them where it's coming from. And instead of freaking out, it just may mean that you have to travel a little bit further to get the hill all the way. Also, apparently, sometimes water and shore lines can change the apparent direction from which the signal is coming. So if the signals coming at over water and then there's a shoreline, it can sort of shear the direction

of it. Um there are some thing obviously, things like metal fences, power lines, buildings can create these reflective surfaces. That will bounce the signal around. Some environments, like cities, are absolutely jammed with radio reflective objects. So if you're in a city, the very buildings around you are just like bouncing the signal back and forth like a pinball, and this can create what's known as a multi path environment.

So multipath is going to be one of the biggest problems to overcome if you are looking for a hidden transmitter, especially in a city or other you know, area crowded with reflective obstacles, and it just means that you're getting the signal, you're tracking from multiple different directions, and you've got to have some experience and knowledge of of how

exactly to work around problems like that. So a good hunter needs to have experience and skill, but they also are going to need, uh not necessarily need, but it really helps to have some specialized equipment, including special antennas

and receivers. Now, as the the authors of that book Joe mentioned point out multiple times, and experienced and skillful hunter can use seemingly inferior equipment and still produce a better result than someone who has lots of money and has dropped it on a bunch of high tech equipment but has little to no experience actually using set equipment. So there is a lot of art to this. It's

not just science. There's a bit where, you know, knowing kind of having an intuition about how radio waves work and the geography that you are in and kind of getting an idea of how that could be affecting what you are are receiving might be way more helpful than just a high tech antenna that is the cost a lot of money. Yeah, um, I I have read all the authors of this book say, and it does seem true to me based also on other things I've read that one of the most important pieces of equipment in

a transmitter hunt is a map. It's having a good map, especially like a topographical map that includes surface features and buildings.

And they also say that, you know, it can become incredibly challenging because the the game doesn't necessarily confine itself to the area of any given map, so you might need multiple maps, and that also becomes a bit of a challenge because unless the maps are both produced at the same scale, you can't just overlay them, you know, and and tape them together or whatever it may be. That it requires a lot of math on your part,

So that's strike against it for me. Well, let's do a real brief overview of some of the main types of antennas you might encounter absolutely transmit on. So we've we've mentioned by names several times the yaggi or yaggy antenna. Um, So this is a directional antenna. There are a couple of major kinds of directional antennas, but a directional antenna, as we've said, it is designed to isolate the directionality

of the signals. So if you point it at a right angle to the signal, you shouldn't be getting much of anything. If you pointed in the opposite direction, most of them should say you know nothing or not much. But if you finally find the direction of the signal, the strength of the signal that comes through the antenna to your receiver should spike yes. And so a yaggy antenna is made of a series of metal elements arranged

in parallel. So if you're trying to picture this, think of one long pole could be like a broom handle or PBC pipe or whatever, and then there are metal rods or wires of varying lengths, and the lengths are very specific and very important. Yes, and they are determined by the frequency of the signal that you're looking for. The relationship of the links of the various elements are very important depending upon what the what their job is. Yeah. Uh,

So there is the most important elements. The main one is the driven element, and this is the electrically active part. Uh. This is the one that connects to the wires that go down to your receiver handheld radio receiver. This is this is what is resonating with that frequency. But then there are these other elements that are known as the parasitic elements, and they're not connected to the receiver, but they're there to manipulate the types of waves that the

driven element receives. This is this is what gives these directional antenna their directionality. Yeah. So the the there's a reflector element that goes behind the driven element. So if you're pointing at the signal source, the reflector elements should be closer to you and behind the driven one. Uh. And it reflects the signal back and focuses is the reception field to the direction that the antenna is pointing.

And then there may be multiple director elements, which are more elements in parallel ahead of the active element to help manipulate the shape of the wave forms and enforced directionality. So if you're looking at these different elements, um, first of all, if you're trying to envision this in your head, imagine that broomstick, all right, the broomstick you are you are holding out from yourself. These elements are perpendicular to

the broomstack stick, but parallel with each other. Right, So at at the closest endto you, you you have this reflector element. It's going to be the largest of those elements. Then you have the just slightly not just slightly and not by a whole lot, and it sort of is acting kind of like the dish in a satellite dish antenna, sort of in that same style. So it's it's slightly larger than the driven element. That's the one that you were you know, is actually hooked up to the sir

so that it's it's pulling in the signal. And then at the far end you have the director elements. These are the shortest of the elements, and again it's not dramatically shorter, it's just a little shorter. All of the size sizes of these depend upon the frequency you're searching for.

I mean, if you want to build a YAGGI for a very specific purpose, you would look at the frequency you're looking for, and there's a mathematical formula you use that gives you the ideal uh driven element size, reflector element size, and director element sizes, and you just it's it's essentially you take a number and you also also their distance from each other. That is also. Yeah, the spacing is also important. The spacing between these elements is

very important. You can't just put them anywhere along that broomstick. You need to have them spaced out properly. So both of those things are very important in order for you to get an antenna that is going to resonate proper with the frequency you want and therefore help you narrow down its direction. Yeah. Uh So then there's another very popular form of directional antenna that is accomplishes the same goal but with a different type of construction, and that's

the quad antenna. Yeah. They they're also typically used to detect frequencies and the high frequency are very high frequency ranges. Uh So they consist of the driven element just and the the direction and reflective element or a directive elements, I should say, uh, just like the yaggi is, but they're arranged in a slightly different way. They use loops of wire. Uh, these loops that are not necessarily in

a circle, they just need to be closed off. So the the example I saw was a cubicle two element quad antenna, and actually it's technically a three element, but because you've got the driven, you've got the reflector, and uh, you know, the direction one, the directive element. I liked it because it kind of looks like a tie fighter. Oh yeah, they look like tie fighter wings loops. Yeah, now that's just the cubicle version. There are other variants

of the quada antenna. Uh. These are these are slightly different look, I mean a very different look from the yogis. Uh. They have a very sensitive directionality to them, and they also tend to have a slightly higher gain than yogis by about two decibels decibel as a sliding scale. By the way, it's logarithmic scale, not so two decibels on its own means nothing. You need to have another point of reference for you to understand what two deciples. But if you've got a weak signal and you need to

amplify it that that could be important. Yeah. So, so quad antennas are a popular way of trying to track down um A signal, especially if you need a little bit more sensitivity than you would with a yogi. Uh So, both of these are popular. They also come in different sizes. I mean, obviously it depends upon what frequencies you're looking for. Uh The quad antenna is interesting because the length of the loop is dependent upon the frequency you're you're searching for.

So the squares in the tie Fighter, like the wing size of the Thaie Fighter, are dependent upon that frequency. And the reflector is actually gonna be slightly larger than the other ones. Uh so. Uh. I was watching a video on how to make this, and that's when I said, I kind of want to make one of these. Um And you know, the mobile ones are slightly smaller than the ones you might mount at your house if you happen to live out in the country and you can

have a forty meter tall antenna in your backyard. Um but they are and it definitely doesn't look like something that's easy to carry around. I mean, they're not they're not small. A lot of people who are serious about this hobby. They have, uh, they have mounts. Yeah, so you'll see vans with these things attached or jeeps that kind of thing, with these things attached to the vehicles themselves mounted on them and they're not meant to be taken off. So uh, that's another popular one. Another one

is the Doppler direction finder. Now this is going to be somewhat different than the directional antenna's. It's still ultimately establishes directionality, but it makes use of the eponymous Doppler effect, named after a Christian Doppler who was known for running down the hallways going E got Dylan laughing on that one. It's just so absurd that Dylan Stern laughing. It's rare that I get our producer to laugh at something, but

that was one of them. Uh No. So Doppler was a nineteenth century uh physicist apparently in my world, slightly absurd one, and he came up with the equations to describe the apparent frequency shifts we perceive that happened from the relative motion of a cinder of a of a signal and the receiver of a signal or a wave. Now you've heard me talk about this before, you probably experienced it. The easiest way to to give an example

is with sound waves. So if you've ever noticed a siren on an approaching emergency vehicle being much higher pitched than it is when it passes you, so it's coming at you, it's a higher pitch noise, it passes you, it's a lower pitch noise. Or if you happen to be next to it and the two of you are either motionless or you're moving at the same speed in the same direction, it may sound like a pitch that's

somewhere in between. That's because of the Doppler shift. When the vehicles moving towards you, it is effectively compressing those sound waves, So it's increasing the frequency, which we perceive as an increase in making the pitch go up. When it's moving away from you, it's elongating those sound waves, and so our perception of that is that it's a lower frequency and the pitch goes down. Same sort of

thing is true with electromagnetic radiation. Actually it's also true with light I mean, which technically is part of electromagnetic radiation, but it's not rad you waves. The same thing is true for all of these things exactly. Yeah, that's how we measure how fast we're moving away from or toward other galaxies for example. Uh So, using a very special type of antenna, you can take advantage of this this

property of physics. So Toppler direction finders typically have several rotating elements and it's usually between three and eight vertically oriented antenna. The antenna pick up the signals that then are sent to a processor that determines where is the signal really coming from? The incoming signal, where is that

coming from? And typically there's like a circular display um that's just a circle of LED lights is the simplest version, and whatever direction the signal appears to be coming from with respect to the front of your vehicle, a little pop up. So it's not telling you that, oh, you need to go northeast. It will tell you, oh, the signals coming this many degrees to your right, or this many degrees to your left, or it's actually coming from

behind you. That kind of thing. So if you were driving due west and the signal at the three o'clock position or the light at the three o'clock position on your little circular display lights up, that would tell you that the signals actually coming from the north, because to your right would be true north if you're going due west.

So you look at this signal the circle of lights, and whichever one is lit up, that's telling you, all right, well, we need to start changing our bearing toward that direction if we want to head in the direction of the transmission itself. Now, another type of direction finder that you could use would be something that's known as time difference

of arrival antennas. And this is another interesting thing. So it it has multiple receiving elements arranged in a pattern that passed the signal along to an electronic computational core that compares the time delay between when the different elements received the same signal pattern. Now this is crazy because remember these signals travel at the speed of light, so the differences are not detectable by humans, right, Like, there's no way that we humans would be able to tell

the difference. And there's obviously easier if you have you know, something where they are multiple elements that are very far away from each other, like installations. Um, but yeah, so you can use time difference of arrival. Since we know the speed of radio transmission is constant, we know exactly what the speed is and we know the difference between the different elements, we can use the time delay between when they receive the signal to calculate the direction the

signals coming from. All right, So we've talked a lot about antennas, and we've we've mentioned receivers quite a few times. Now. Some people listening maybe thinking that what you're doing is you've got a pair of cans on your ears and you're listening really carefully for the beat beat beats. But as it turns out, most of the time we're actually talking about a piece of equipment that indicates when it's receiving a signal and giving you an idea of how

strong that signal is. Let's talk about that for a second. Well, so it is going to be a receiver radio receiving radio receiver you might be familiar with, but the most useful ones, obviously are going to be ones that are equipped with what's known as an S meter. So you've got your antenna and you've got a wire running from your antenna to the receiver or wires running from the antenna to the receiver, UH, and the receiver should be able to translate the signal into something you can make

sense of. That might be sounds, or that might be a number, and in the case of an s meter, it would be a number. It's a gauge that gives you a direct reading in a numerical value of the strength of the signal. So you're not just relying on you know, subjective and sans from listening or some other method. So you just find the direction where the number on the estimeter is the highest. This makes it a lot easier, and the signal strength is going to increase the closer

you get to the transmitter. There's actually a very specific amount where you can sit there and say, like, all right, I look to see when the the strength of the signal has doubled. That gives me an idea of how much closer I am to the transmitter. But using you know, describing that requires lots of calculations and variables that I don't really have the time to go into right now.

But just general rule of thumb, you know, you're you look at that signal strength, and that gives you an idea of how much closer you are to the transmitter without actually giving you any sort of units, Like it doesn't tell you, oh, it's a mile away or it's a thousand yards away or anything like that. It just tells you, oh, you have had the distance between you and the transmitter. Whether that distance was ten miles or one mile, who's to say, It all depends upon the

strength of the transmitter. So yeah, uh, so you mentioned when you get close. Another important factor is going to be that most of your equipment is going to be attuned to weak signals. You want to be able to

detect a signal coming from a long distance. But when you get close to something that is uh you know, you you is no longer a weak signal, it can overpower your equipment, right, so you might suddenly you've got your receiver and you've got your directional antenna and you can point it around in a circle, and no matter what direction you pointed in, your smeter is maxed out

because you're just you're just too close. It's it's it's like, you know, the water is completely around you, so detecting where the water is coming from is not easy to do, right, So in this case, another piece of equipment that some people might have that would make a big difference would be known as an attenuator. And so yeah, in in this case and attenuators an electronic element that can help you knock down the power of the signals, sort of

the opposite of an amplifier. Uh, and so that your equipment can tell which direction the signals strongest and not just be maxing out at the top of the esimeter. Right. This is also when the harmonics can come into play, because if you can switch to the third harmonic or the fifth harmonic, then you're using weaker signals and it is less likely to overwhelm your equipment. Now we've been talking about, you know, antenna types and stuff like that.

If if you are a HAM hobbyist and you want to build something, or you want to spend some money in order something on the internet, you can have these uh, these interesting setups that will give you a big advantage. But people, some of these hams will talk about how you don't actually have to have something like that to do ham hunting, ham hunting, transmitter hunting. You are the HAM.

I've I've hunted ham before ham The most dangerous game it was there was, Uh, there was this time where I spent with a bunch of my school friends on an island hunted HAM. I don't like to talk about it though didn't turn out well to serve Ham. But one example of an interesting hack for crude tea hunting. If you don't have a directional antenna, but you've just

got a standard receiver handy talkie. You know, uh, is this thing that I read about called body blocking or body fading, which doesn't involve tackling somebody, you know, But this is a really interesting idea. So let's say you've just got a little handy talkie. The antenna on this

thing is omnidirectional, right, like a standard radio antenna. It directs, it listens to all directions equally, right, So if you're picking up a signal, you can't tell where it's coming from, just you just know that you are within range of that signal. But here's what you can do. You take your regular omnidirectional antenna and press it tied up against your chest, hug it to your body. Now stand in place,

and rotate your body slowly. You should find, actually that your reception will be fine in most directions, but that it will deteriorate when your back is facing one direction. And that's because you're suddenly that's the direction where you're putting your body directly between the transmitter and your receiver. So it's called body blocking because you are physically blocking

the signal from getting to the radio effectively. Yeah, sort of the opposite of a directional antenna here, because you instead of saying go to where the signal is strongest, you find the direction where you are most able to block the antenna from receiving the signal, and then you know that your butt is facing the transmitter, as is always the case with me. Yeah, I like this idea. I like the idea of actually holding a competition that only allows for that sort of transmitter hunting. I think

it could be really interesting. It would also be really interesting to see it from afar, like being able to see at least three or four Like you're just seeing these people turn around very slowly, stop and then immediately do a one E D and start running in that direction, all passionately embracing their little handy talkies. Yeah. Yeah, and again, like before you brought this topic up to me, I had never I'm not a ham radio operator. I've never

gotten into amateur radio. I think it's fascinating, but i've never it's just not that's never been a world that I've explored, so I didn't even know that this was a thing when you brought this up and learning about it, I'm like, you know, this is it does appeal to me because just as geo cashing and letter boxing and those other forms of of kind of using technology to help hunt down something. It's kind of cool because that, you know, it does had that relationship between technology and skill,

and that that desire for us to uncover secrets. I mean, I think that's something that's kind of innate in humans, right, This desire to to the scavenger hunt is very powerful thing because it's just it's fun to go through that experience and to uncover mysteries and stuff. And they're all sorts of different variations on these uh these these competitions, Like one of them I would read about everyone starts

in the same location. Everybody starts there, and everyone gets their initial bearing and then it's up to them to figure out how to get to Usually a sequence of transmitters, with each transmitter sending out a slightly different variation of the signal, and typically they would do this over the course of several minutes, So like on minute one transmitter one is transmitting its signal, then it shuts off, and then transmitter two emits its signal and then it shuts off,

which means that if there's like five transmitters that you have to find by the end of the day and you have just missed, like you hop out the car. Yeah, if you hop out of the car a minute too late, then you have to wait another five to ten minutes before your transmitter comes back online. So you could could It's it's you know, time management, it's it's orienteering, it's

all this sort of stuff. And I'm like, wow, what a neat idea, And I would love to to participate in one of these, But I think we should do it as like a small group of us and shoot it on video and do it kind of like how some of our car stuff buddies did an interesting project not too long ago. Oh wow, yeah, be kind of neat. Of course they probably first tea hunt. It will mostly end up with all of us yelling at each other,

but that could be entertaining to watch. Joe, thank you so much for coming on the show and bringing this topic up. It was a lot of fun to look into. Um, why don't you let people know where they can find your work here at how stuff Works. Well, you can come and listen to the podcast that I do, Stuff to Blow Your Mind, with my co host Robert Lamb

and Christian Seger. We are a science and weirdness podcast here in the How Stuff Works family, trying to pull back the curtain on the oddust corners of the universe. And so yeah, come check us out Stuff to Blow your Mind. We've got a website, stuff to Blow your Mind dot com. And of course I also write for video here at how Stuff Works. If you check out our channels like brain stuff, you'll see some of my intolerable work there. And Jonathan, I hope to come back

on the show sometime again soon. Absolutely, it's always fun to have someone else in here. Uh. It breaks up the narrative versions of the tech Stuff podcast, which is nice for me and I'm sure my listeners agree. Guys, if you have any suggestions, questions, anything like that, you want to send me a message, you can do so via email. The address to send it to is tech stuff at how stuff works dot com, or you can

drop me a line on Facebook or Twitter. The handle I use at both of those locations for this show is text stuff. H s W and I'll talk to you again really soon For more on this and thousands of other topics. Is it, how stuff works? Dot Com Want