On Thursday, July 11, 2013 12:41:11 PM UTC-4, dave wrote:
On 07/11/2013 09:38 AM, Michael Black wrote:

On Tue, 2 Jul 2013, dave wrote:





You forgot to turn on the BFO. BFO level is frequently too low for

demodding SSB hence the need to reduce RF gain.



No I didn't. It should be a given that you need the BFO. I was making

the point that it's one of those radios of the time that didn't have a

product detector, so you had to do what all the books said to do. A few

years later, most receivers did have product detectors. Indeed, the

GPR-90 came along right at the cusp, so you could get an external unit

that added a product detector (and I think some extra selectivity) and

some really fine tuning. The receiver has the an IF output jack on the

back, even has a jack for feeding audio back into the receiver (though

the TMC adapter had a built in audio amplifier). Other receivers had

similar units. The R388 and the R390 didn't have product detectors,

though they are considered some of the best receivers from the time (and

perhaps for all time).



But with that level of receiver, turning down RF gain wasn't a real

issue. I had no problem receiving SSB, even on six meters, on the SP-600

I had forty years ago.



ON the other hand, that Hallicrafters S-120A (the transistorized model)

that I got in the summer of 1971 had a horribly weak BFO, so by the time

I'd attenuated the incoming signal (a pot between the antenna and the

receiver), there weren't many signals left strong enough to receive.





I've had a couple R-390As. I used to leave them on 11175 upper with RF

gain low, carrier sliced off with 2 or 4 KC mechanical filter by

slightly tuning off center, BFO on about 1200 cycles. It was dead quiet

unless someone spoke, like dolby FM. It would stay perfectly tuned for

days, with the ovens off.



I can't afford electricity to waste on old radios.

My R-390(not A)got drowned in seawater last year, during the storm called Sandy . Now I don't know what to do with it...