Thread: 4NEC2?
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Old October 14th 18, 11:01 PM posted to uk.radio.amateur,rec.radio.amateur.antenna
Ralph Mowery Ralph Mowery is offline
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Default 4NEC2?

In article , lid says...

On Sun, 14 Oct 2018 12:04:52 -0700 (PDT)
Jeefaw K Effkay wrote:

On Sunday, October 14, 2018 at 7:33:10 PM UTC+1, Jeff Liebermann
wrote:

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.


I've seen this explanation before, but it doesn't make sense.

A 9MHz USB signal mixed with a 5.0 to 5.5MHz VFO will produce mixing
products in the 80m and 20m bands - but both will be upper sideband.






When the 9 MHz is mixed with the 5 mhz the 20 meter signal is upper
sideband. The 80 meter signal is inverted and becomes the lower
sideband NOT usb. Years ago when ssb was just starting out on the ham
bands this made 80 meters and 20 meters easy and inexpensive compaired
to other methods. So it was decided on by hams to use 40 metes and
lower frequencies as LSB and 20 meters and above as USB. Then the
government stepped in for the 5 and 10 MHz bands and dictated what to
use.

For other reasons most digital is in the USB mode for all bands except
for RTTY. RTTY is usually used in the LSB mode for all ham bands, but
can be used in the USB mode if the tones are inverted. The commercial
RTTY was usually inverted from the normal ham RTTY.