A little something different for today’s article, and maybe something to play around with if you have some time this weekend. I’ve found you all some circuits and construction information for Video Transmitters, a 5V power supply, and a GPS tracker.

VHF Audio Video Transmitter – A really simple audio and video transmitter for creating your own video sender. The VHF band is typically available on older TVs, since most newer TVs are only able to tune into UHF signals.

VHF Video Transmitter – a more powerful, but still simple video transmitter circuit.

Vehicular 5V Power – a regulated 5V power supply capable of smoothing the spikes in a vehicle’s 12V power supply. Useful for many microcontroller projects which require a stabilised power supply so that you don’t fry the chip. Microcontrollers can be used for many security projects, such as remote control bugs, sounds activated bugs, controlling devices with relays, alarm systems, etc.

AVR based GPS Tracker – A location tracker using an AVR microprocessor that integrates a GPS module with a GSM module. You call up the GSM module, and then it replies by sending the GPS coordinates to your phone in a text message. Please note: the destination site requires free registration to access the information.

The Everyday Practical Electronics (EPE) Magazine is the number one hobby electronics and computer projects magazine in the UK. Their focus is on practical circuits and projects, and the magazine features a number of smaller useful circuits in addition to those featured on the front cover.

I’ve long been a reader of their magazines, and even collected most of them for a while. Foolishly, I gave most of them away a few years ago when I was clearing out. However, they do offer a back issue order service, so I can get any issues I really want. EPE recently started an online version of the EPE magazine which makes it easier and cheaper for non-UK electronics enthusiasts to get hold of.

They have a very helpful online forum called Chat Zone, where you can get help, advice and even help others too.

If you want to improve your knowledge of electronics for building your own spy circuits, or simply want to gain enough knowledge to hack your own spy gadgets, then I recommend EPE very highly.

GSM Trackers are great low-cost tracking devices, but they will only give you the location of the tracker within a 100 metre radius. So if you’re tracking something in an urban area, a 100 metre radius is a very large area indeed. A great way to solve this is to use a localised transmitter to track down the device within this radius. Think of a GSM tracker as being a coarse tracking device, and a localised transmitter as a fine tuning tracking device.

A localised transmitter is simply a ‘bug’ that transmits a continuous tone or beep. This can then be received using a radio scanner with a signal strength meter (such as the Icom R2 Radio Scanner). If you have a directional antenna, you can get even better results. The concept is simple, you move in the direction in which the signal increases in strength. As you get closer to the transmitter, the stronger the signal.

If you want to try your hand at a localised tracking transmitter, I found one that was recently updated. It may look complicated, but you get plenty of stability (as in the frequency doesn’t change as the transmitter warms up) without using crystals (which add lots of complexity to a circuit).

The site that hosts the circuit diagram features lots of other spy circuits. So you’ll enjoy looking around!

You know the films in which there is some devious labyrinth of laser beams which some hero has to get through in order to steal something of great value or to save the day (such as Mission Impossible or Entrapment), well how about making your own laser tripwire system?

The system uses a laser pointer type device, rigged up to a light-sensitive resistor, a PIC and an electronic security alarm. It’s a really simple system, but does need some basic electronic and programming skills (for the PIC). I can imagine the fun of setting up 10 of these with semi-visible lasers… it would be so cool to show off to friends!

While looking around on MAKE Magazine, I found a useful little circuit for a telephone bug. I know how much you guys love circuit diagrams!

The bug is a serial device, which meals the phone connects to the bug, and then the bug connects to the telephone line. This means that only that particular phone is bugged. Potentially, you could build the bug into the phone itself.

The design is suited to the US phone network, not sure if it’d work in the UK. You can substitute 4 1N4148 Diodes for the IN4384 Diodes too.

In a recent article, I discussed the difference between parallel and series telephone taps. In this article, I present a very simple and reliable parallel phone tap circuit useful for recording telephone conversations onto a tape recorder.

When installing a telephone tap, its advisable not to cut the telephone line in anyway. Cutting the telephone line for any time is detectable, and therefore series devices can be detected in this way. Parallel devices can be installed without cutting any telephone wires, and is thus harder to detect.

The diagram shows a simple circuit using just 6 very cheap and common components. To build the circuit, you’ll need some Veroboard or prototype board (whatever you favourite is), some wire, and a 3.5mm plug that will connect to your tape recorder’s microphone input socket. I’ve left it to the reader to work this bit out, as its very simple to do but quite awkward to explain!

To test the circuit, connect the telephone line wires to pins 2 and 5 of the telephone line. Then plug the microphone input into your tape recorder. Pick up the telephone and press record on your tape recorder. You should be able to hear a dialtone on the tape when you play it back.

If you’re curious to what goes on in the circuit, I’ll explain that now. The resistors act as a potential divider, and limit the voltage from the phone line that reaches the recording device. The diodes ensure the incoming voltage is rectified from an alternating current (AC) to a direct current (DC), which might otherwise damage your tape recorder.

The capacitors should be a ceramic type, rated at 50V or more. The emphasis is that the capacitors should not be polarised, which would stop the circuit from working properly. The resistors can be 1/4 Watt carbon or metal film types. As you can see, the components are very cheap.

The circuit is designed to work on UK telephone lines. However it should work in other countries too. You may need to adjust the resistor values to get the best volume. To increase the volume to the tape recorder, increase the value of R2. If the sound on the tape recorder is distorted, then try decreasing the value of R2 to decrease the volume.

If your tape recorder has a voice activated system (VAS), then you can set your tape recorder to record whenever the phone is used. You just need to adjust the recording to trigger when the telephone handset is lifted.

In a flash of inspiration, I thought visitors to SpyReview might appreciate circuit diagrams for various surveillance circuits. Therefore I have started a new category of posts on the site called “Circuits” (duh!).

To start things off, here are 3 FM audio bugs, designed to be powered by batteries. One is low powered, and 2 are high powered. The latter two, due to the 3 transistor stages, will be more stable and therefore will not drift in frequency as much as the 1 transistor version. The designer is a well-respected RF circuit engineer.

Audio Bug Circuits:

Wireless Microphone by Harry Lythall – a basic FM bug using a single transistor and common components. Can easily be made into a tiny package.

Wireless Microphone 2 by Harry Lythall – a low power FM bug with 3 transistors for excellent stability. It will probably eat batteries though.

40mW FM Transmitter by Harry Lythall – a 40mW high power FM bug with 3 transistors and relatively few components. This will eat batteries too.