On 12/27/2011 11:27 AM, Jim Thomson wrote:
> Date: Sun, 25 Dec 2011 13:34:03 -0800 (PST)
> From: Commander John<firstname.lastname@example.org>
> Subject: Re: [Amps] Fwd: Linear Amplifier Tuning---PROPERLY!
> I fail to see how having spurious sidebands at -20, -30, -40?or whatever
> makes the??????????????
> Signal wider.? The sidebands are still there regardless of final?suppression
> ### You are confusing sidebands with IMD. This is NOT FM. It's SSB.
> IMD is caused by non linearity.
> It is the receiving stations receiver having the rejection ability that
> reduces received?interference.?
> ### wrong again! IF station XXX using his ICOM on TX....is 10 khz
> wide... then he's 10 khz wide. If you are 3 khz away, you are now screwed,
> and there is no filter on the the planet that's gonna do any good. He's
> Txing on your RX passband, so his TX IMD is now overlapped with your RX
> Having adjacent sidebands that are stronger than necessary causes a
> receiving station to hear these sidebands at a harmful signal?strength
> further away from the transmitted frequency than if they had supression at a
> highter level
> ## It's adjacent IMD, not sidebands.
> A legal limit station would have much stronger IMD because it is stronger not
> wider.? It only is preceived as wider because they are stronger than from a
> 100 watt transmitter.?
> ## That all depends on how loud his IMD is to start with. But yes, if 2 x
> stations have the same IMD... but one is 10db louder than the other [say a
> bigger ant or amp].... then the station with the 10db syronger signal will
> also have IMD that's also 10db stronger. Which is all the more reason to
> have a cleaner signal when u have a big amp, and big towers' ants etc.
> ## No point in all these deluxe receiver's with 100db dynamic range. It's
> of now use,and pointless on ssb. Not until the TX IMD gets improved on
> these ham xcvr's. The Icom's are 10 khz wide when u stuff white noise into
> them...and the yaesu 5000 in Class A is only 3.5 khz wide [both measured at
> the -45db point]. The bands are NOT crowded . They are just jammed full
> of sub standard xcvr's..which is most of them.. with junk TX portions. If
> everybody got heir act together, you could easily double the number of ssb
> signals on a given band. You could triple that if everybody had class A, or
> the eq.
Just think what the bands would sound like if we were still using SSB
rigs from the 60's<:-)) Even the Collins and Hallicrafters were not all
that great. There were exceptions, but not many.
Of course it's not just crappy IM from many of today's SS rigs. Many of
them give the operator so much control over the signal they end up
generating garbage up and down the band quite a ways trying to find what
they think is the perfect, tailored audio. "I think" if you find
noise/splatter/buchshoting more on one side than the other it's probably
related to IM as IM can be much more prevelant on one side than the
other. OTOH over driving the amp usually ends up with buckshot and
splatter pretty much equal on both sides. Neither is likely to result in
a nomination for "ham of the year".
> Jim VE7RF
> john W9ZY
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