LIPD frequency assignments (from ACMA
Frequency range (MHz)
29.7 - 29.72
30 - 30.0625
30.3125 - 31.00
36.6 - 37.00
36.625 in this band
39 - 39.7625
40.25 - 40.66
40.66 - 41.00
run from one 1.5 volt cell.
Measured current drain 11mA @ 1.5 volt (15mA @ 4.5 volt)
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
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
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.