What I used to like about Tandy (pre Woolworths) is that they provided an alternative range of components to DSE stuff, especially things like switches, relays and bezels.

Altronics still sells valve sockets and some valves --- mainly those for guitar amps.

I have emailed the article to Maven & Tinkera123

Yell if anyone else wants it. (approx 1mb .zip)

ben

Ben,

Received .... thank you.

Ian

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Cheers, Ian

Me too.

I've compressed Redxm's files one 5-page PDF at about 480kb if anyone would like me to pass it on.

I've collected 6-7 circuits now, ranging from Wa2wise's top-of-the-line 5-valve job and the HRSA complex solid-state design down to one that uses nothing more than an audio transformer, a 1meg crystal oscillator, and a 9volt battery.

Still studying and weighing up options and cost-benefits.

Maven

My study of many options was cut short by a kind member of this Forum offering to send me a Silicon Chip 1993 Fleapower transmitter that he had built from kit and was no longer using.

It came beautifully packed, minus the coil, but I found that the Jaycar 200uH toroid that I had used while failing to build one of the other circuits did the trick, and I have a fully functioning Fleapower.

With that gift, I turned my mind to packaging. It came in the standard jiffy project box. My aim was to build a "Trannymitter" into the shell of a transistor receiver. The sacrificed model is a cheap Chinese-made Pye from about 1990, courtesy of K-Mart if I remember correctly.

I gave up the idea of using the receiver's tuning condenser to make the transmitter fully tunable. The SC Fleapower is tuned at around 770kHz with a trimming circuit that gives about 10kHz leeway - enough to dodge strong local stations.

The photos show that the Fleapower PCB fits into the battery compartment of the Pye receiver, which gives convenient access to the trimmer and to the post-and-socket connections that I made to connect the Fleapower to the interface of the Pye case.

Audio In uses the earphone socket on rear of the case.
This passes via the old receiver's volume potentiometer, to regulate audio input. The same pot switches power on-off, switching the ground side of the 12v circuit.

I wired in the radio's original power LED as well, adding a 47k resistor since the working voltage is bumped up from 6 to 12v.

The radio's AC power supply transformer had failed years ago, though the half-wave rectifier is still there and works. I decided it was cheaper and safer to use a 12v DC wallplug than to buy a new 240-12vac transfomer to revive the receiver's PSU.

The tranny's telescopic antenna works fine at a range of a couple of metres, which is how it will be used. For a perfectly clean signal reception I can just run a loose wire from the Trannymitter's antenna to the receiver's antenna. No longer "wireless", but none the less still AM modulated.

Thanks again to all who offered advice, circuits and encouragement.

Maven