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RE: side band
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Anonymous post on October 28, 2005
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See Element 2 questions T2B11 and T2B15.
http://www.arrl.org/arrlvec/tech2003.txt
Amateur bands above 9 MHz use USB, below 9 MHz use LSB. Exception is 60 meters where it is channelized USB.
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RE: side band
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by w8syd on October 29, 2005
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Interesting bit of history there. Back when SSB got it's start, HF was 160, 80, 40, 20, 15, 10 only. I don't know for sure, but the likely reason for those bands is that they are all harmonically related. So one VFO frequency could give you all bands.
The first SSB rigs were phasing types which were a bit of a pain to use. They soon gave way to crystal filter rigs. Many of the early crystal filter rigs were 80, 40, 20 only. Because you can use either the sum or difference frequency from a mixer, a single VFO band of 5-5.5 MHz could be mixed with a 9 MHz Upper SSB signal to produce LSB on 80 and USB on 20. So what started out as a less costly way to produce 80-40-20 rigs became a standard. Everything below 9 MHz is Lower, above is Upper, with the exception of 60m. The higher end rigs of that time, and nearly all rigs today, were double conversion and the 9 MHz fundamental had two sets of filters to produce either sideband on any band.
I still have a National NCX-3 (circa 1960) which was one of those early 80-40-20 rigs. There were enough of them around that they established the tradition.
It is a tradition only. You can use LSB or USB on any of the bands, except 60m. Theoretically, if you have good clean signals, you can have two QSOs on a single frequency, one upper, the other lower, and not significantly interfere with each other.
73,
Byron, [email protected]
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RE: side band
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by W9WI on November 27, 2005
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Some early SSB transceiver designs used a 5.0-5.5MHz VFO and a 9MHz IF.
9+5 = 14
9+5.5 = 14.5
9-5.5 = 3.5
9-5 = 4
So these transceivers could work both 20 and 80 meters without changing either the VFO or the IF. But the subtraction process flips the sideband -- if you feed USB into the mixer you get LSB out -- so with that design you're going have opposite sidebands on the two bands.
The decision to use USB on 20 and LSB on 75 (instead of the other way around) I suppose would have been pure chance.
At the time phone was not permitted on 40 (?!) so the fact that this design didn't support 40 wouldn't have been a serious problem.
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