"Per Stromgren" wrote in message
...

One last one, while I have I have you guys on the line: will the drift
"amplitude" of component values grow with age as well? Otherwise, it
would just be a matter of re-tuning, but that does not seem to help in
the normal case. These radio set drift away happily while listeing.

Yes, probably.

Also, a more serious problem is that the parts are drifting away from each
other. Thus, initially the radio had everything right in the center of the
desired range, and there was lots of tolerance for drift. Now, parts have
already drifted apart so that the working range is very narrow. That is, if
one IF stage goes up in frequency and the other one goes down, the range
where they overlap is much smaller than before -- so if something else then
drifts, it will be much more likely to have a noticeable effect.