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Cambridge Kits
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VLF Receiver
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Extend your coverage down to 10 kHz with this Very
Low Frequency Receiver, 10 - 150 kHz, direct conversion for morse, 50 k ohm input
impedance for 15 m antenna, needs 12 V at 10 mA, 4 x 7 x 13 cm, 250 g.
"very interesting to hear stations on VLF", FR in High Wycombe,
Bucks.
"excellent little set", THR in Worthing.
"neat and works very well", CGM in Jersey.
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This fun-to-build kit includes all parts, case, connectors, screws etc
as well as detailed assembly and operating instructions.
The kit includes a ready-cut piece of copper laminate
and full size foil pattern for easy drawing,
etching and drilling of the printed circuit board.
The board is 3.7 inches long, single sided with wide tracks
and generous spacings as shown here
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and the kit includes ordering details for etch resist pen and ferric chloride.
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If someone wants to offer a PCB (drilled or undrilled) for this kit,
then their contact details can be announced here. |
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VLF ATU
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Take the output from the emitter of T1 in the 100 - 600 kHz Converter,
via a 100 nF capacitor.
Add 33 mH in series with L3 to tune down to 15 kHz.
This works well with a short antenna.
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ULTRASONIC
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Use an inexpensive 40kHz transducer to the antenna input
to detect high frequency sound from gas leaks, bearings running dry or bats -
attract them by throwing a tennis ball high into the air at dusk.
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