In message , Phil
Allison writes
Ian Jackson wrote:


** Not really possible since the FM band is only 20MHz wide.

For a low side local osc:

88.1-10.7 = 77.4 = lowest local osc f

77.4+20.0 = 97.4 = highest local osc f

97.4+10.7 = 108.1 = higher f than any station.

I'm pretty sure that the local oscillator nearly always runs 10.7MHz
HIGHER than the radio signal.


** In the examples I have checked ( both tube and SS ), it was always
10.7MHz lower.

Then don't you get a lot of image trouble from the two TV channels below
the FM band?

Makes the LO more stable is one reason.

I would think the benefit would be pretty marginal.

While I'm sure there are exceptions, regardless of the frequency they're
receiving, there are probably very few 'normal' radios or TV sets etc
where the LO runs below the tuned frequency.





--
Ian