This is a real problem in older 100Mc FM band radios. I had a Zenith that would drift after it was on for a while. I think I changed every component in the radio until I finally tried a new converter tube. Any similar experiences?

-- The Tube Man (vacuum@tube.com), March 23, 2002

Answers

In a tuner that I am currently engaged in designing, FM conversion will be done using a 12AT7 dual triode tube to help avoid this problem. In addition, the unused diode section of a 6H6 dual diode will be used for a defeatable FM AFC circuit. The other diode section is the AM detector-AVC. This should aleviate any problems associated with drift.

-- The Tube Man (vacuum@tube.com), March 25, 2002.