LIPD Beacon

Following on from Simple Radio Beacon (HF):
This is a modulated VHF low power beacon in an LIPD spectrum assignment (36.625MHz).
(LIPD = low inteference potential device) see AMCA document:
Radiocommunications (Low Interference Potential Devices) Class Licence 2000

LIPD frequency assignments (from ACMA documentation)
Frequency range (MHz) Max' Power Notes
29.7 - 29.72 100mW
30 - 30.0625 100mW
30.3125 - 31.00 100mW
36.6 - 37.00 100mW 36.625 in this band
39 - 39.7625 100mW
40.25 - 40.66 100mW
40.66 - 41.00 1 watt


Will run from one 1.5 volt cell.
Measured current drain 11mA @ 1.5 volt (15mA @ 4.5 volt)
However 3 or 4.5 volt battery supply makes for a stronger RF signal



I used a quartz crystal salvaged from a defunct 2 metre ham radio: 12.20833 MHz
Orignally frequency multiplied by 12 would give 146.5 Mhz
Repurpose in a JFET type xtal oscillator with the collector LC (tank) tuned to 3rd harmonic i.e. 36.625 MHz (12.20833 MHz x 3)
A 700Hz multivibrator provides audio modulation, and is gated on/off by 2Hz multivibrator.
Once again I had to use all discrete components, as they are the only circuits which work with a low supply rail like 1.5 volt
Audio is AC coupled into a tap near the earthy side of gate-source resistor (4.5%)
Off-air reception indicates both AM and FM modulation!

FM, then AM then USB reception



I have returned to "cardboard-tronics" for this construct!
Components are physically mounted on white cardboard,
where a white card "substrate" allows folding around corners!
Discrete component ends "pushed-thru" small holes
and all connections are soldered into "quigg’s"
(pigtail spirals formed by winding small gauge wire around a small drill shaft or sewing needle etc)
into which all connections are inserted and flowed with solder.
A reed switch activated by an external magnet serves as an on/off switch.
Compact assembly fits inside a piece of 50mm PVC tube.





See also: pocket metal detector (cardboard-tronics)