Spy Circuits

VHF spy circuits or Very High Frequencies circuits can transmit for a long distance. For that reason, you should check what laws you have in your country on fm transmitters. Here is the circuit, let's see how it is built:

http://www.zen22142.zen.co.uk/Circuits/rf/davidtx.htm

Building a wearable microphone is nothing more than building a small fm transmitter circuit. This wireless fm mic is an fm transmitter and can transmit about 100 meters.

That's not too bad of a transmission range. It is fine if you are close enough to the person wearing the microphone.  This has very few parts and can be built relatively quickly.

(source  - http://www.flashwebhost.com/circuit/fm_wireless_mike.php)

This spy circuit only contains 5 components which makes it very simple to build. For a listening device, this is very tiny but given that it is tiny, it can only transmit a limited distance.

1 - 10nF, ceramic. Preferable NPO type
1 - 20pF adjustable trimmer cap
1 - 74LS13
1 - A crystal mike
1 - Small wire for an antenna
 

Shoot, you are probably thinking, where do I find those parts? For the 74LS13, I would try getting it from Digi-key. Here is a link to a search I did there for it: 

Creating a telephone bug is not all that difficult. The idea is twofold, you must create a transmitter and you must allow the phone signal to continue. If your transmitter is noisy or has a lot of static, then listeners are going to hear that. So you have to get the signal but not interfere with it on its way and then you have to get it somewhere else and not have it easily detected. This FM telephone bug is a simple start in that direction. Remember that this is just for the radio theory. This has many applications which are not illegal.

Creating a listening device that can transmit conversations or sounds for a longer range can be valuable in surveillance. This FM bug can serve a variety of purposes from listening to sounds, conversations, nature sounds, and other things. Building a listening device is rather easy to do.

If you are looking to transmit audio transmissions for a good distance but need something small to do it, then this micro spy circuit would be a good one for you.  This very small spy circuit takes very few parts.

This micro FM bug is fairly small. About the size of a small matchbox and it is a neat little project to work on because it uses surface mount componets. Surface mount components are smaller. If you are working on them, buy a good soldering iron. I recommend a Hakko soldering iron. They are great and then you can get a special tip for doing surface mount soldering. Here is a link to the transmitter. It costs about 14 dollars. Alternatively, you can source the parts yourself and then make your own circuit board.

I saw this facinating idea where to transmit a phone converstation an unlimited distance another phone was put inline with the first phone's phoneline. Then when a call is made on the outbound phone, the second phone dials you or someone else and allows the original call to go through.  It's expensive though, so pretty much out of reach for the common person. I guess though if you could program a cell phone to precall a certain number, that would work though but it would take some programming.

http://www.advanced-intelligence.com/telephone.html#!au488

If you want to check out a circuit that is already built, consider this small device off of Ebay:

http://cgi.ebay.com/Inline-FM-Telephone-Bug-~-Inside-DSL-Filter_W0QQitem...

However, remember to check the laws in your area before proceeding with using a device such as this. And if you were to use a device like this, you should inform those listening that you are transmitting their conversations.

This FM telephone bug is somewhat compact. It is however, on the FM band, so that's a consideration to make when building it. Wouldn't it be bad luck if you bugged someone's phone and they happened to hear themselves talking while their radio was on. Of course, bugging a telephone is illegal in most areas so this is just for the theory of it all.