Bill:
I have a comment about the question of the
LSB/USB convention mentioned in the most recent SolderSmoke podcast and
the follow up blog post:
I checked the 2006 Handbook and there is a sidebar
(page 9.27) explaining the 5/9 MHz connection with the Lower/Upper
Sideband convention in use today. It explains that there was a popular
rig that used a 5 MHz VFO and a 9 MHZ IF that were mixed to create the
75/20 meter RF signals. This is certainly a reasonable method, but
would not result in the inversion. The article then goes on to explain,
however, that other rigs used a 5 MHz tunable IF and a 9 MHz local
oscillator which would indeed result in sideband inversion and thus the
convention we use today.
73,
Jeremiah, KB0OFF
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I sure would like to take a gander at that article.
ReplyDeleteHow could that configuration work as an SSB exciter?
As Chuck Adams would say, "Inquiring minds, etc."
73.......Steve Smith WB6TNL
"Snort Rosin"
Steve, a 5 MHz tunable IF could have been either a phasing exciter or mixed up from a 455 kHz crystal or mechanical filter (plus either 4.5 - 5 or 5.5 - 6 MHz as the VFO).
ReplyDeleteThe resultant 5 - 5.5 MHz output could be mixed with a bank of crystals for various HF amateur bands. Ditto on receive - crystal controlled converters feeding a tunable IF was a popular way of building a stable high performance amateur band only receiver).
Because SSB was most useful for DX having 20m was a must. Mixing with a 9 MHz crystal also providing a bonus 3.5 - 4 MHz (with inverted sideband) which cut costs.
By the way SSB for the Radio Amateur (1970) describes using 5.5 MHz xtals for the filter - cheap as these were surplus items. This would have inverted the sideband if subtracted from a 9 MHz VFO.
K9STH gives another explanation at http://forums.qrz.com/archive/index.php/t-125756.html with regards to early commercial rigs. 73, Peter VK3YE
I'll agree with the phasing theory using a 5.5 MHz SSB generator and a 9 MHz LO to generate either 3.5 LSB or 14.5 USB but since a phasing SSB generator will switch sidebands with the addition of a simple DPDT switch, it would be much easier to use a fixed 9 MHz SSB generator and a 5.0 - 5.5 MHz VFO. Also there's no worry about the RF phasing 'slipping' as the LO frequency changes.
ReplyDeleteOn the AC6V website "WHY LSB BELOW 9 MHz AND USB ABOVE" (about half way down the page), 3 entries clarify these issues:
Karl-Arne Markstrom SM0AOM
Jim N2EY
Alan Larson WA6AZP
Most of the other stuff under that heading is bogus or at least unclear.
73.......Steve Smith WB6TNL