"Steve Kavanagh" wrote in message
om...
A year or so ago I was working on a microwave local oscillator (at
about 2.5 GHz) multiplied up from a crystal oscillator near 40 MHz.
The output was found to jump in frequency by tens or hundreds of Hz
many times as the LO chain was warming up. I was able to reduce this
jumping by replacing all the dipped silver mica capacitors [...snip]

The capacitors used in both cases are from unknown sources and were
probably manufactured in the early 1980's.
Has anyone else experienced this behaviour ?
Steve (VE3SMA)

Steve,
Although I didn't figure it out at the time, my Knight-Kit Space Spanner
circa 1960 had terrible microphonics - very noisy. I cleaned the entire
chassis & rewired it to no avail. Today I suspect a mica cap, the old
square type, since I heard of same thing this some time ago.