13

IMO, your question is too general to give a good, specific answer. Also, it would help if you elucidated the motivation for the question. I am a semi-retired electrical engineer, not a security or RF expert but I'll give it a go anyway. The first assumption is that the transmitting equipment is hidden from plain sight and other non radio-related detection. ...


12

The best way is to get a high gain antenna, and figure out what direction it's coming from. Do this from 2-3 points. Take a map, and draw lines from each of the point of origins from the direction you heard the signal the strongest. That should give you at least an idea of where the signal is coming from. Once you have a rough idea, the next step is to go ...


11

Another possibility to look into is meteor burst communication. This is a well-established technology. You beam a VHF signal up into the sky, it bounces off a meteor trail, and your recipient picks up the reflected signal. Since transmission is upwards, picking up the transmitter's location would require being above the transmitter at the time (making ...


7

There was a similar problem in the US a few years ago and it turned out to be a new shop sign that had a defective ballast that emitted a wide RF spectrum. Most key fob systems operate at frequencies of 315 MHz for North American made cars and 433.92 MHz for all others. The direction finding equipment would involve a programmable receiver or a portable ...


5

As discussed, yes it's perfectly legal to receive anything. It's the transmitting that is regulated. One easy solution is to not use a transceiver at all. Since the transmitter half of the device is your problem. So take the transmitter out of the transceiver and you end up with just a receiver. So what can you use as a receiver? The simplest thing to ...


4

Here is my dumbed-down experience. If you are looking at T-hunts. I have always made sniffer loops about 1/10th or less then actual wavelength. Many times we would add a trimmer-cap across the antenna feed point but most the time would not. Even before I was a serious ham I did this quite successfully on the CB band for "Skunk Hunts" where we would all ...


4

Essentially this involves using your body as a barrier to fade the signals. Holding the HT close to you, and rotating until you get the weakest signal, then the source of that signal will be on the other side of you. In an answer to a different question, WPrecht - AB3RY quoted the following Handie-Talkie Tricks tip from Joe Moell, KØOV's Homing In website: ...


4

In general, reception of radio signals does not require a license. (Even if a government wanted to try, it'd be nearly impossible to regulate - after all, there's inherently no emission from a reception-only station, so there's no way to tell it's even happening.) A license is only required for a transmitting operator. The HTs you're using for the hunt are ...


4

at least in the world where I come from Assuming this is the world of arrogant computer security experts (sorry I'm a bit allergic to this): Well, unlike computers, physics wasn't designed by humans. So, any signal that contains significant information needs to contain significant power (that's a direct result of Shannon capacity), and if it has significant ...


3

I suppose that a very rough estimate of the general location of the transmitter could be made by comparing signal strengths of several receivers with omnidirectional antennas without knowing exact details of the antenna systems of the receivers, but the estimate will be very approximate. That's not a very practical technique. A better technique is to have ...


3

In my club we do many things to make sure the fox is not stolen / thought it was a bomb / hide it. Here are a few things. Our main fox is inside one of those old surplus 50 cal. ammo cans. It is pretty large making it very visible. A good thing about though is it is (custom) painted with a camo pattern that fits our area quite nicely. We also have someone ...


3

I would bend the tips back, twisting the free end around the standing end so you make a loop with good electrical contact between them. Measure from the base to the end of the loop for the purposes of calculating the length. The loop is almost entirely cosmetic and won't affect the electrical length of the antenna much. If you were to make the loop bigger, ...


3

There are two kinds of "loop antennas". There are resonant loops, which are loops where the length of the loop is long enough to be resonant. These can be considered folded dipoles, which have been folded into a loop. A quite distinct antenna is the small loop. These antennas have a perimeter that is electrically small, meaning less than one-tenth of the ...


2

Yes they can. You are right that the cheap HTs don't have much of a useful meter (I own a couple). Two easy solutions are 1) body fade and 2) directional antennas. Body Fade Hold your HT close to your chest and turn around slowly, looking for the direction where your body blocks the most signal (the signal null). Now you know that the signal is coming ...


2

This should work fine. These cheap Chinese HTs don't have many bells and whistles, but they are decent radios especially with non-stock antennas. For beginners I would start with some real simple scenarios and fairly open terrain. You don't want a ton of multi-pathing scatter to confuse the new hunters. See my answer to your other questions for some ...


2

Prior to having your event, contact the police who cover the area where you plan to place the unit. Explain that its a Training Aid for rouge signal detection. Offer to bring the unit in to have them examine. Explain the placement and the time that it would be located there. Its mounted the way it is to both protect and hide its location from your searchers....


2

You can build a special rig that will give you direction finding capability with a standard radio here: How would a time-difference-of-arrival receiver with two antennas know which side the signal is from? It works by switching between two antennas, located less than a wavelength apart. If the two antennas are exactly the same distance from the ...


2

Would this help? A cheap and simple yagi that's been used for fox-hunting before. http://www.arrl.org/files/file/ETP/The%20tape%20measure%20antenna.pdf Here's a youtube vid from AmateurLogic.tv https://youtu.be/PqTH42NRMck?t=30m8s As far as the payload you lost - does it currently have the micro-fox installed? If so, have you tried taking a 2m HT out to ...


2

First the answer: When I worked for the forest service I built single-transistor transmitters where one of the leads of the transistor was the antenna. It doesn't get any more simple than that. They used hearing aid batteries. Then we could enclose them in beeswax so we could stuff them down the throats of animals, even snakes. The batteries would last ...


1

I remember an episode of the live action TMNT series in which Mike had a pirate radio station. To make detection harder, the transmitter was in his truck. I believe everyone here has been thinking about stationary radio sources so far. By keeping your transmitter moving, and going dark as needed, you may avoid detection for a while longer. They will only be ...


1

There are several techniques. first physically hide the transmitter and antenna. While this is hard for large antennas, it becomes more feasible at higher frequencies. I read a story about a HAM radio fox hunt where the fox (transmitter / antenna) was hidden in a coed's swim suit as she was sunbathing in a park. The hunters knew the transmitter was in the ...


1

If the reason you're having trouble with body fade is that you can hear the signal no matter what, then you need to make the signal weaker, so that you can hear the difference in how well your receiver is picking it up. To do this properly, you use an attenuator between the radio and antenna. But of course, that's also equipment you need to buy or make (a ...


1

I would make something discrete, as sudden changes are easier to detect than large ones. Stick into the middle of the hearing range (Many Hams are older, and tend to lose the extreme hearing range with time). I would choose a random sweep of tones in the 1000-1500 Hz range, changing the tone 2-5 times per second (Random time intervals might also work). This ...


1

If a simple magnetic loop antenna is what you want, you should have a look at http://www.m0ukd.com/Magnetic_Loop/ The loop he constructed is about 10cm in diameter (which is approx. 4 inches) which is not that much to carry around. For 70cm you might want to go for a small Yagi design since it provides you with some additional gain. For a 4-Element yagi ...


1

I take part in four main activities as an activator: Worked All Britain World Wide Flora & Fauna Castles and Stately Homes on the Air (affiliated to the World Castles Award) Summits on the Air (although this one has become rarer) For all three activities, I've ended up in parts of the UK that I would probably not have visited, and seen places I wouldn'...


1

For me, the ability to interact in real time with a person on the other side of the planet and get to know them a bit has been lots of fun.


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