On Sun, 14 Oct 2018, Jeff Liebermann wrote:
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.
Actually with filter rigs, they used only one filter. Military rigs might
use two filters, obviously especially if they did ISB, and there must have
been some ham rigs, high end, that used two filters, but generally it was
one, and the BFO crystal was switched.
There's more to this story, but I can't remember at the moment.