UHF Set-Top Converters for early UHF broadcasts

[Robert Grant]

I saw many of these at secondhand stores and hamfests in the early 1980's, and used one regularly back in those days.

They actually found new popularity after the all-channel act was passed, as new UHF stations came on the air and people were stuck with VHF-only sets.

Most UHF converters had a very simple circuit. A power supply powered a 6AF4 oscillator (in later models, a transistor or tunnel diode) which, 76 or 82 MHz below the frequency of the desired station, mixed, in a germanium diode with the station's signal, converting the UHF station to channel 5 or 6.

As one might imagine, this essentially passive conversion took a LOT of UHF signal to produce a usable picture.

One good question: Is it legal to possess a UHF converter today, post-ECPA? (since it is a device designed to receive frequencies that have since been reallocated to Part 22).