Re: LSB on 75 Meters (was: US 60 Meter Band Changes...)

Posted by KU4AF on Nov 22, 2011; 9:04pm
URL: http://elecraft.85.s1.nabble.com/US-60-Meter-Band-Changes-Approved-by-FCC-CW-Issues-tp7012018p7021971.html

Whatever the genesis of the LSB/USB convention on the ham bands, this conversion scheme wasn't it. Mixing a 9 MHz USB signal with a 5 MHz VFO will produce a USB output on either 4 MHz or 14 Mhz. The sidebands only get inverted in a mixer when you subtract the SSB signal from a higher frequency LO.

This "ham legend" has persisted literally for generations despite frequent debunking. Maybe we can eradicate it by teaching our grandkids that "We had to use LSB back then because DSP hadn't been invented yet."

John, KU4AF
Pittsboro, NC

w5tvw wrote

<snip>
The reason this was done was due to the conversion process employed  as the
SSB signal was generated at 9 Mhz and heterodyned to either 14, or 4 Mhz
with a 5 MHz VFO signal.  Whichever position of the mode switch was used
(SB1 in all probability, it's been too many years for me to precisely recall
and not really important at this time for me to research it!)  At any rate,
the result was Upper sideband signals on 14 Mhz and lower sideband signals
at 3.8-4.0 Mhz.