On Sun, 14 Oct 2018 18:50:34 +0100, Brian Morrison
On Sun, 14 Oct 2018 10:42:24 -0700
Jeff Liebermann wrote:
For what it's worth, I don't know which sideband to use on 40m.
For data modes it's just about all USB, and has been for some time.
But it's easy to see why people can get confused and wonder what they
set up incorrectly.
No need to beat anyone up about it, just explain if you're asked.
I don't think I'm beating up on anyone, but if an explanation is
required, I can do that.
It might help to understand why some bands use LSB while others USB.
In the early daze of sideband radio, the common IF frequency was 9MHz.
The radios had only one sideband filter. With one filter, it was
cheaper and easier to mix and up convert in the transmitter. So, to
save the cost of adding a second filter, the bands below 9MHz were
designated as LSB and the band above 9MHz became USB. Eventually,
radios were built with two sideband filters, and this was no longer
important. As usual, the legacy technology remained in place to haunt
the survivors to this day.
The problem repeated itself with the rise of the digital modes. People
wanted mult-band radios, but didn't want two filters in the radio.
So, someone flipped a coin and decided that everything should be USB
when using digital modes. For example, with JT65A, it's USB on all
I'm not quite sure if that's also the case with other digital modes.
For example, PSK31 (BPSK) doesn't care if you use USB or LSB, but by
convention, USB is preferred.
For marine radio HF communications, it's all USB.
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