On Dec 15, 2:05�am, Phil Kane wrote:
On Thu, 13 Dec 2007 20:27:37 EST, (Mark Kramer)
wrote:

The story I heard is that this started because Collins radios had an IF
of 9MHz and only needed one set of (expensive) sideband filters to have
LSB below 9 and USB above. Mixing to get the final output: F1+F2 gives
same sideband you start with, F1-F2 inverts.

That's what I was told.

The real story is that it was the Central Electronics (CV ??) exciter
that had that scheme.

Yes, the CE 10A, 10B and 20A exciters all used a 9 MHz SSB
generator. They were quite popular in the 1950s.

But they could not be the source of the amateur LSB/USB convention,
because that scheme does not invert the sideband on
either 75 or 20.

73 de Jim, N2EY