From FB group Vintage Transistor Radios
For the last few months, ever since I started experimenting with oscillators on the AM broadcast band, my attitude towards auxiliary audio inputs has changed. Earlier I thought that it would be convenient to have an aux input. But I was leery of making changes to the collectibles radio circuits that might affect their value.
Instead I use an AM oscillator next to the radio. I’ve built a few of the oscillators and they are cheap, easy to make, stable and can be easily modulated. They can be powered by a few AA or AAA cells or a 9V battery, and use low current so the batteries can last. The headphone output can be used to modulate (AM is monophonic only), or another transistor can be added to give the higher input impedance that an auxiliary input has.
