Hello, All!
I believe there was some brief discussion in this forum recently about what
Leif, SM5BSZ, has to say about / showed about transmitter noise and a
variety of commercial rigs currently in use. The URL in question was:
http://antennspecialisten.se/~sm5bsz/dynrange/ssa2004/ssa2004.htm
Leif is an extraordinary individual who has brought immeasureable benefits
to those of us doing weak signal VHF work and EME.
His current interest is in the limitations of current commercial rigs as
regards the purity of their transmitted signals. He basically found exactly
what Pete, AC5E is noting. ALC, Key clicks,and phase noise are in currently
used rigs the 3 main causes of problems in transmitted signal purity, if I
read Leif's words correctly. And it looks to me like ALC and key clicks
[which can be reduced in some cases by turning off the ALC] are 2 things
that at least with some rigs we can do something about, by turning off the
ALC. So there is something we can do at the end-user stage to compensate
for design flaws of the rigs we use.
Interestingly, there was essentially 30 dB variation in the phase noise at 5
KHz from best to worst among the radios Leif tested.
73,
Roger
W3SZ
----- Original Message -----
From: <ac5e@comcast.net>
To: <tentec@contesting.com>
Sent: Sunday, May 09, 2004 8:22 PM
Subject: Re: [TenTec] new emissions rules
> Well, partition noise is not a major contributor to TX noise. But it's
still there - along with all the other classic noise sources I learned about
between WWII and the "Korean Police Action," as well as some that weren't
dreamed of even thirty years ago. And a few noise makers have been reduced -
Johnson noise in particular is generally less than it was in hollow state
devices.
>
> The major contributor to spurious emissions seem to be phase noise and ALC
circuits that cannot react quickly enough to limit the power output to
nominal or reasonable power output without adding severe distortion products
to the RF output. Both of which should have been taken care of in the
initial design stages.
>
> Of course, CW rise and fall time can contribute to key clicks. Since I
have no ambitions to be a high speed CW op I keep the Orion set at 6 ms
which seems to satisfy the guys across town and raise no complaints on the
air. If I were slower I would slow rise time and fall times down and if I
were faster I would be forced to decrease it.
>
> That's just one of those things. High speed CW takes more bandwidth, and
the faster transition that's necessary for shorter characters may create
clicks. As long as they aren't the extreme sort covering several kc, kHz, I
hear so often from the "bottom two" of the "big three" I don't complain a
lot. Mutter under my breath, maybe!
>
> 73 Pete Allen AC5E
> --
> Never squat with your spurs on
> > Thanks for the info regarding paritition noise as it applies to solid
state
> > devices I was under the false impression that partition noise was
generated
> > only by boat anchors! Since Ten Tec is primarily solid state (except
for
> > amps) their equipment was partition noise free.
> >
> > 73, Jim
> >
> >
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