"Scott Dorsey" wrote in message
...
EADGBE wrote:
I went to a garage sale recently and couldn't pass up an old Technics
SA series receiver in great condition. (A Technics SA series receiver
was my first bit of halfway decent stereo equipment.)

Your notion of "halfway" is sort of optimistic.

The receiver's FM tuner works great and sounds very good, but I can
only get the "FM Stereo" indicator light to light up on one station,
even though the signal strength meter indicates VERY strong FM signals
on almost every station all across the FM band.

Odds are the stereo detector stage needs alignment or else it has some
other issue with it. Take it to a tech. The audio output of the
FM detector goes through a coupling cap into a second discriminator
stage. All kinds of things can go wrong with it.

I only have one of those little clear-coated two-conductor wire FM
antennas hooked up to it right now, but if I recall correctly, that
was all that was needed to get FM Stereo on virtually every station in
my area.

Could something be weak in the FM tuner circuitry, or do I need a
stronger antenna?

No, the stereo demodulation circuit is bad.

And whilst I'm at it, what is the functional difference between the
two 300 ohm FM antenna terminals and the grounded 75 ohm FM antenna
terminal, besides the obvious difference in resistance?

If you have a 300 ohm source, you use the 300 ohm input. If you have
a 75 ohm source, you use the 75 ohm input. Usually there is a balun
inside the case which transforms one to the other, and the balun is
a little lossy, so one of the inputs will have slightly better
sensitivity.
Which is basically academic since you will need the correct one for your
source anyway.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

To add to Scott's reply:- The 300 ohm input will be balanced twin feeder.
This is the cable with two parallel wires, spaced about 12mm (1/2") apart.
The 75 ohm input is unbalanced and uses coaxial (screened) cable. In the UK,
we prefer to use the 75 ohm input as screened cable protects the antenna
signal from interference, especially from mains wiring and/or metal objects
which could change the impedance of the balanced unscreened cable.

Having said that, Scott is right in that if you have a 75 ohm antenna, use
coax, if you have a 300 ohm antenna use balanced twin.

S.



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