On Thu, 21 Mar 2013, Brenda Dyer wrote:



"marc" wrote in message ...

Can you listen to a speaker in this BOX ? Do you need a computer for the
processed sound?

http://www.ebay.com/itm/TG37-SSB-BFO...em 2567fc55c1


thanks,
Marc
--


--------------------------------------------------------------------------------
--------------------------------------------------------------------------------

My best guess is that it outputs a stable carrier wave at the radio's IF
frequency, with the exact output frequency tunable by ~ +/- 3 KHz so that the
proper sideband can be tuned.

LIkely, and of course that sort of thing used to be relativelyc ommon, in
the hobby magazines as construction articles, and even as store bought
additions.

That said, the ebay description is so garbled that it's hard to tell.
They talk about an f connector, which initially I'd assume is the antenna
connector. If that's true, then the unit may put a signal on the signal
frequency, injecting at the antenna. Those had the advantage that if they
were well stabilized, they'd stay beated against the signal while the
receiver might drift, the receiver drift only cause attenuation of the
signal as it moves across the passband, while the BFO was still in the
right place in reference to the incoming signal. It also meant that the
BFO could be nice and weak, since it's amplified through the receiver,
just like the incoming signal. The disadvantage is that the unit has to
be stable or else you are constantly retuning it, and you may have to hunt
to get the BFO signal on the needed frequency.

The other thought I had wsa I think the 450 has an IF output jack? If
that's what the type F connector is, then they may be using the IF out
jack to inject the bfo signal into the receiver. That may not be the best
place to inject it, depending on where that IF out jack is connected, but
it means that one isn't constantly tuning the BFO since it is at the IF
frequency.

Of course, that IF out jack is for connecting some external detector, and
one might as well add a product detector as well as a BFO and then some
audio amplification. Or add a whole synchronous detector.


Or add a receiver that tunes 455KHz and use that for demodulating SSB. It
was good enough in the days of the Command Set receivers (that one with
the 85KC IF that tuned some low frequency up to about 550KC) adding
selectivity and a BFO, though if you had a receiver that did that, it's
probably better than the 450 to begin with.

Michael