4 ms·
The Wadley Loop (2019)
- mikewarot 6y agoThe National Radio HRO-500 used an HFO to generate 500 kHz steps, and a separate fairly linear VFO for the last 500 kHz of tuning. The use of a manually tuned pre-selector stage helped greatly with image rejection. It had a variable frequency first IF, which then tracked the VFO tuning, and the second IF was at 230 kHz. It came out about 1962, and I helped a friend repair a few of them in the last few weeks. All the transistors were in sockets (Germanium transistors, which do seem to age and get "weak")