"Per Stromgren" wrote in message
...
On Thu, 12 Aug 2004 05:01:01 -0500, "Mark D. Zacharias"
wrote:

Many radio's suffer from alignment problems as they get older. This
applies
to digital models also, but not so much, since they have fewer
adjustments
and are somewhat self-compensating. Station frequency, for example, won't
drift, but component values do somewhat, meaning VCO and discriminator
alignments may need to be re-done.

I probably won't do that, these sets are selled by the dozen, but out
of curiousity: what components values can drift with age?

All component values drift with age. Your problem seems to be temperature
sensitivity or voltage sensitivity. For example, if the supply voltage to
the local oscillator drifts then the frequency will be affected. When you
are listening to an FM station at 100 on the dial, the local oscillator is
running at 110.7 MHz and a drift of only 0.1 % will throw the tuning way
off. That's why older receivers used AFC and newer ones use PLL frequency
synthesizers for the local oscillator.