Browse over 10,000 Electronics Projects

Transistor Radio Series – The 7 MHz Scratch Synthesizer

Transistor Radio Series –  The 7 MHz Scratch Synthesizer

[Section Five — Photos]

Above — All 4 boards were built in re-purposed Hammond boxes.

A PIC-based counter sits on top of the offset mixer. I build modular gear and this allows modification and fosters experimentation. When I build a final transistor radio receiver, I plan to place the offset mixer, PLL circuitry and VXO on the same board inside the radio with some shielding. My VCOs always go in a RF tight container. A 0.0033 µF feed through capacitor connects the VCO varactors to the outside world.


Making this project I learned much and like my VCO + mixer, the sublime loop filter and also avoiding toggle switches by running local MOSFET switches. I’ve already extended the MOSFET switching technique in a more complex PLL for a scratch UHF synthesizer.


— All 4 boards on my bench

Above — Main VCO output in a DSO.

Pages: 1 2 3 4 5 6 7