"Jean-Marie" wrote in message
...
"Thierry" To answer me in private use
http://www.astrosurf.com/lombry/post.htm wrote in
:

Hi,

Technical question requested by a ham:

Is it possible to receive an image signal on a low frequency on USB
mode and find the true signal at some higher frequency in LSB (e.g.
6.1 mhz usb and 7 mhz cw-lsb). It seems that some UA stations emitting
on 40m have their image on 6 (e.g. 7043 - 6135 = 907 / 2 = well IF 454
khz) but a reversed mode ... ?? Looks really strange if not
impossible.

Thierry





An image frequency always have it's sidebands inverted. That is part of
the reason why amateurs use LSB on 80 and 40 metres and USB on 20 15 and
10.

One of the first SSB transmitter had its IF between 40 and 20 metres and
the sideband was not switchable. So the result was LSB on 80 and 40 and,
USB on 20 15 and 10. It became a de facto standard.

Note that there were only 5 HF bands at the time.

Jean-Marie

Exactly right Jean-Marie. 9 MHz IF was used and a 5 MHz VFO- adding for USB
on 20M and subtracting for LSB on 75M

Dale W4OP