In article , Phil Allison
writes

"gary"

My Fm4 has a strange problem, I have replaced the back up battery and this
is working, if I store a station at 88.10 mhz when I switch it back on the
frequency comes up at 88.00 mhz for the first 5 - 10 minutes, it then
slowly creeps up to 88.5 then 88.10, it does this on all stations stored.

Does anyone have any ideas about this


** I take 88.5 should be 88.05 ????

So the tuned frequency drifts up by only about 100 kHz as it warms up -
NOT 500 kHz.

Despite appearances, the FM4 is NOT frequency locked with a digital
frequency synthesiser, like most other tuners with a digital readout.

Tuning frequency is controlled by analogue circuitry via "varicaps " - so
cannot be entirely drift free.

What is that locked to if anything, or is it free running with AFC?.

Doesn't seem to be an FM4 circuit in the web anywhere.....

However, the digital readout shows the ACTUAL operating frequency of the set
with high ( ie crystal ) accuracy.

There is likely NOTHING wrong with your FM4 - so leave it alone.

Please disregard my earlier post.




....... Phil

--
Tony Sayer