[R-390] R-390 AProduct Detector

[2002tii]

Mark wrote:

> A forth [SSB option] is to add a separate SSB detector/BFO at the IF
> Out. Several Mil-Surplus detectors do this, as well as the Hammarlund
> HC-10. The latter has the advantage of providing notch filters and
> bandwidth filters, though it is expensive at about $300.

> The latter option just got a lot cheaper if you have access to a
> reasonably fast PC. A lot of Hams are playing with a little device
> called a SoftRock.

One issue with outboard detectors is that they often don't feed an AGC
signal back to the radio, so the AGC won't be based on the signal you
are listening to. This is easy enough to do with the 390A, and I
believe some of the Mil units do it. It's not necessarily a horrible
problem, but it's not optimal, either, particularly if the outboard
detector has its own IF filters.

I have always intended to design an outboard IF section with its own IF
filtering, selectable upper, center, and lower BFO injection, 2 or 3
tunable notch filters, a product detector with synchronous detection
capability, and an AGC feed. The ideal implementation would switch the
BFO offset with the IF bandwidth, so the upper or lower BFO would
always be just outside the selected passband. But I have always had
other, more pressing projects....

Best regards,

Don