[Elecraft] SSB IMD

[Julian, G4ILO]

Jan Erik Holm wrote:
> 
> As I said before, here I am first time on 20m
> SSB and people report trash around my signal,
> i e bad IMD. However at that time I had K3 at
> 120W, aftter I´ve made measurements and it
> looks like something slowly starts to happen
> at 80W.
> Also I have myself heard K3´s on SSB with "trash"
> around the signal "however" I have also heard
> K3´s that did NOT have that.
> So what´s going on here, I´m getting reel puzzled
> and frankly quite tired of this.
> 
This sounds similar to what I was noting on PSK31 when I experimented with
higher power levels. However someone else commented the figures I gave were
surprisingly high, so I did some more tests and found that on 20m I am
getting -34dB PSK IMD right up to 100W output! However the poorer figures
which I measured on 30m are repeatable.

I'm not sure what to make of this and I am using an amateur PSK meter not a
lab grade spectrum analyzer so at this point I am not sure if I can believe
the measurements. I am going to see if I can substantiate the results
receiving off-air using another receiver and computer. But your comments, my
results (and the Eham review causing so much concern in some quarters, which
mentioned SSB splatter on 17m) could indicate that there is a variation in
PA linearity from band to band that might make some rigs clean on some bands
and not on others. Why might this be?


I wish there would be a "service manual" available,
like there is for any Japanese rice box. I mean
a manual that contains all data for all adjustments.
Why not??


It should not really be difficult. After all the K2 was designed to be built
from scratch by people with nothing more in the way of test equipment than a
DVM and a dummy load. Probably the only adjustable setting is the bias
voltage, though I haven't looked at the schematic since it isn't something I
personally wish to tinker with.

-----
Julian, G4ILO. K2 #392  K3 #222.
http://www.g4ilo.com/ G4ILO's Shack   http://www.ham-directory.com/ Ham
Directory    http://www.g4ilo.com/kcomm.html KComm for Elecraft K2 and K3 
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