The Ten Dollar Bug
by Thomas Icom

For those whose surveillance budget is less than that of a third 
world nation and don't care about sophistication, this little gem 
will do the job at the bargain price of $9.99 plus tax.

The device is the Radio Shack FM wireless mike kit (28-4030). 
Soldering will be required. It operates on the FM band between 80 
and 106 Mhz, and according to Tandy's catalog will run about 40 
hours on a 1.5 volt "N" cell.  The instruction sheet states that 
it's range is 45 feet.


My Observations

All things considered, it's a decent unit for the price. The mike 
sensitivity is a bit lacking, but it lends itself to some 
interesting modifications.

The circuit design is capable of running off of more voltage than 1.
5 volts. Doing so will also increase your transmitting range. I ran 
one off of a 9 volt battery without any problems.  At 13.5 volts the 
unit still held together, but what stability the unit had went to 
hell.

The heart of this unit is a 2SC1923 transistor (a/k/a ECG107). This 
transistor is usable to 800 Mhz. By changing the component values 
for capacitor "C4" and coil "L", you'll be able to move the unit off 
of the FM broadcast band for increased security.

Even Cheaper

If you're so destitute that even ten bucks is too much, the Radio 
Shack kit is comprised of about eight dollars worth of parts. The 
design is such that you'd get away with constructing it using point 
to point wiring, provided you stay on the lower frequencies. 
Personally, I think that when one takes into account the time of 
waiting to get the parts from a mail order house, the typical $20 or 
so minimum order that most mail-order parts dealers require, and the 
time and the fact that the Radio Shack kit has a nicely laid-out PC 
board all ready to go for you; that you'd probably be just as well 
off spending the extra two bucks and getting their kit.

Final Analysis

It's no crystal controlled Deco unit.  Then again it doesn't cost 
$70 a pop either. At $10 it definitely falls into the throw-away 
category. I use mine for a few internal applications where security 
isn't a concern, like wiring it to the speaker jack of one my 
scanners, so I can use an FM radio to listen in while working around 
the house.  The unit is easy to put together, and lends itself to 
experimentation.