"Beeping" Tracking Transmitter Kit

(two sizes...FM108K and FM108KS)
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With these Kits you can build a very small tracking transmitter that can be tracked using a FM broadcast band radio receiver (105MHz to 108MHz). The transmitter can be powered from any 5 to 12 volt direct current battery or power supply. They have a range of 1/8 mile to 1/2 mile depending on battery voltage, height above ground, receiver sensitivity, and antenna length. Under certain conditions distances of 1 mile have been achieved. The kit comes in two sizes.  "FM108K" is 1/2" by 2 3/4" and uses "through-the-hole" standard sized components.  The "FM108KS" uses one surface mounted integrated circuit and 3 resistors mounted on the foil side of the circuit board and is 1/2" by 1 3/4" (including the battery). The "FM108KS" requires an experienced builder due to the very small size of the surface mounted IC. These circuits are designed for model rocket locating, however, it can also be used as a beacon on cars, boats, kites, balloons, and people.

Free Plans...



FM108K Beeping Tracking Transmitter 108 MHz Kit (FM broadcast band)... $15.00 USD
FM108KS Small Beeping Tracking Transmitter 108 MHz Kit (FM broadcast band)... $15.00 USD 


Frequency  105MHz to 108 MHz adjustable
Mode  FM
Transmission beeps
Size (large)  2.75 x 0.5
Size (small)  1.5 x 0.5
Weight (large)  16.3 grams (0.6 oz) includes battery
Weight (small)  10 grams (0.4 oz)
Battery life (using 23A battery)  5 hours
Range without counterpoise (5 feet above ground)  300 feet
Range with counterpoise (5 feet above ground)  1320 feet (Air to ground ranges of a mile have been reported)
Receiver  common FM broadcast band FM radio or VHF2 receiver *
  *All range tests done with VHF2 receiver
Use  Model Rocket and model aircraft locating
Other  standard through-the-hole components

* It is recommended that this transmitter be used with FM radios that can tune continuously across the dial. The better the receiver and receiver antenna system the greater the practical range of the transmitter. Functionality can vary widely depending on the radio used. The VHF2K receiver kit was developed as an inexpensive high sensitivity receiver to be used with these transmitters. The VHF2 receiver works better than the standard commercial broadcast band receiver for the following reasons:

1. It can receive weaker signals ( more sensitive).
2. It does not have an automatic gain control so, the closer you get to the transmitter or when it is pointed most directly, the louder the signal.
3. The shielding of the receiver and the nature of the regenerative receiver makes it much better at direction finding and makes it possible to achieve good results with a small antenna.
4. The receiver is very wide band and receives both AM and FM modulation concurrently.
5. The VHF2 plans are free and a kit is available.

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Copyright ,Jerry Baumeister