Cheapest, Easiest throw away audio link.

[XXL]

Iv heard it done before. Just not sure how easy it will be. I doubt You’ll be able to link very far. The signal would have to be very strong.

[Polecat]

Yes distance is an issue but it's cheap and has one big advantage - the source isn't associated with the tx. Thanks again for responding

[Albert H]

I know a couple of stations that just "walked the receiver" a little out of band, and linked with a couple of hundred milliwatts on 108.3 MHz. It's not actually in the airband, but can't be received by ordinary receivers.

My favourite - used very successfully and safely for many years - was the mains link. If you were in the same building, ideally on the same mains phase, you could get superb quality through the mains wiring. The transmitter was a VCO running at around 140 kHz, through an amplifier stage and a coupling transformer to put 140 kHz FM into the neutral and earth. Upstairs, the receiver was a coupling transformer feeding an amplifying filter stage then a squarer, so the signal became a FM square wave. This went to a PLL demodulator which gave recovered audio to feed to the rig.

My clients using this set-up then wanted to go stereo, so I had to build another mains link at 350kHz with much wider deviation. The stereo coder was at the studio end, so the signal going up the mains was multiplex modulated 350 kHz FM. The receiver was the same sort of circuit as above, but the resultant output was composite MPX!

The mains links cost <£20 at 1980s prices.