[Collins] PRC-47

[Dr. Gerald N. Johnson, electrical engineer]

LSB and USB are legal in ALL ham phone bands. Its traditional to use LSB
on 80 and 40 meters because that was convenient when the first home
built radios ran upper sideband on 20m with a 9 MHz phasing IF and a 5
MHz VFO. Sum made 20m USB, difference made 75m LSB. In theory one could
switch sidebands in the phasing exciter, but the audio phase shift
networks of the 50s were not good enough so when one tuned for decent
opposite sideband suppression on the first sideband, flipping the
sideband switch required complete retuning because the tune suppression
might have been as good as 40 dB, with the switch flipped (inverting one
audio line) the suppression might have been detectable at a few dB. So
the phasing rigs were ONE sideband only. And the mixing schemes
determined the sidebands on the various bands.

For a good 25 years I worked USB on 75 meters on a weekly sked with my
dad and we found that overlapping opposite sidebands tended to be less
obtrusive than overlapping the same sidebands. E.g. more signals can be
squeezed in a band if half are USB and the other half LSB. This is not
commonly recognized.

For those on 75 or 40 who grumble about USB being "upside down," the
proper retort is "I feel upright."

73, Jerry, K0CQ
-- 
Entire content copyright Dr. Gerald N. Johnson. Reproduction by
permission only.