Transmitter Question(s)...

[seebic]

Okay, quick outline first... I am wanting to transmit a tone or voice signal at 50 Khz. As in, I want to broadcast on the 'radio-station' 50Khz (I know that I can't transmit on that frequency without a license over a distance of 10 feet... : D not a problem). I just need to find a transmitter design that can be modified to broadcast at that frequency. <p>I also need a design for a receiver... at the same frequency. You had to see that one coming!<p>Does anyone have any ideas as to where to find such designs/schematics?

[russlk]

You will find an oscillator schematic here: http://www.electronics-tutorials.com/os ... lators.htm
To modulate the oscillator, connect the drain to the collector of your audio amplifier instead of to +12VDC.
You can modify the local oscillator in an AM receiver to pick up 50kHz. Connect a capacitor in parallel with the oscillator coil. You may have to experiment to find the right value, try 1000pF to start.

[Dean Huster]

Down in that vicinity, there are a lot of license-free bands. Can't transmit over 10 feet? No. You can transmit as far as you want as long as you don't interfere with licensed stations. The 10 foot thing is antenna length. On those license-free bands, the length of antenna PLUS feedline must be less than 10 feet and your power level is limited. There's a really neat low-frequency book out there, but I'm not sure if it's still in print. It was a vanity press or privately done publication and my copy is in storage where I can't get at it at the moment.<p>Dean