Posted by
Sandy W5TVW on
Jun 18, 2004; 2:55am
URL: http://elecraft.85.s1.nabble.com/K1-on-USB-CW-tp367868p367889.html
It goes back to the original "SSB Jr." which was ultimately the basis for the FIRST
real commercially built SSB transmitter, the Central Electronics 10A.
It was a phasing rig and, the SSB selector was simply labeled SB1 and SB2.
Since 75 and 20 were the "popular" bands then for SSB (there wasn't a 40 meter
"phone" band back then!) the operators were "lazy" and used the SB1
position for both bands (as I remember) yielding LSB for 75 and USB for 20.
Commercially and on the marine bands, USB has been the standard since day 1
and far as I know. Why the amateurs have hung onto this old LSB on 40
and below thing I don't know. I forget whether the 10A/10B/20A used a
5 or a 9 mhz channel for SSB generation, but it DID "flop over" when
you went from 20 to 75 meters! Must have been generating SSB at 5 Mhz.
Anyhow that IS how that LSB/USB phenomenon got started: just plain
laziness!
Maybe one day they will mandate USB as the "normal" sideband? Didn't
they state that on the 60 meter channels? (USB only?) I'm sure that was
to get around the stupidity of the "monitoring" personnel who obviously
used receivers with USB filters only and they didn't know CW! I thought
it was a stupid move to "channelize" the 60 meter band on SSB only!!!
I supposed ARRL has too many irons in the fire now with the "rehashing"
of the amateur classes/privileges and BPL to worry about 60 meter
mode expansion?
73,
Sandy W5TVW
----- Original Message -----
From: <
[hidden email]>
To: <
[hidden email]>
Cc: <
[hidden email]>
Sent: Thursday, June 17, 2004 4:34 PM
Subject: Re: [Elecraft] Re: K1 on USB CW
| In a message dated 6/17/04 2:41:52 PM Eastern Daylight Time,
|
[hidden email] writes:
|
|
| > The present day LSB - USB band "standards" have their roots
| > from years ago in the availability of 9 Mc crystals / filters - when
| > SSB was experimental and you had to build your own. 9 Mc plus a VFO
| > running at 5.0 to 5.5 Mc gives you 20m USB. Subtract the VFO frequency
| > and you tune "backwards" on 75/80m and you get LSB.
|
|
| No, that's just not true. Urban legend. I believed it for years but when I
| did the math the truth could not be denied. The only way you get sideband
| inversion is if the heterodyne oscillator is above *both* the input and output
| frequencies of a mixing process.
|
| Yes, the 9 MHz IF / 5-5.5 Mhz VFO scheme was popular, and it does result in
| one band tuning backwards. But it *does not* result in sideband inversion!
| Generate USB and 9 MHz and mix it with a 5-5.5 MHz VFO and you get USB on 75 and
| 20.
|
| The LSB/USB convention for hams goes back to before hams used 9 MHz filters
| to generate SSB. .
|
| Now if you use a 5 MHz SSB generator and a 9 MHz VFO you *do* get sideband
| inversion.
|
| If anyone wants the exact math, I have it all written up.
|
| 73 de Jim, N2EY
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