Making a K2/100 Cleaner

[Jim Brown-10]

In preparation for Field Day, I had occasion to set up my HP8590D
last night and do comparative measurements of what my K2/100 and
TS850 looked like 300 kHz away. I was surprised by the result.

With both radios, I transmitted CW on 3515 kHz and looked to see what
the SSB team would be contending with between 3750 and 4000 kHz. The
TS850 was cleaner, by roughly 15 dB, than the K2/100. Transmitting on
7025 and looking at 7150-7300, the TS850 was roughly 6 dB cleaner.
Comparable tests on 14 MHz showed them pretty much even money.

The K2 is s/n 3003. Several other hams built the various pieces of
the K2/100, which I bought used, and their work looks quite clean.
I've owned it for about a year and a half and been quite pleased with
it. Both radios were matched to an indicated 1:1 VSWR using their own
antenna tuners (the KAT100 with the K2), and working into the same
antenna through a switch. This radio DOES have the key click mod. The
K2/100 is >40" from the nearest power supply.

So the question is, what can I be doing to get my K2/100 cleaner "in
band?" Are there specific mods that are likely to accomplish this?  

And I recently bought an old-timer, s/n 301, identically equipped
(K2/100, KAT100, K160RX, KNB2, KDSP). I'm currently troubleshooting
an AGC problem in that radio, so it's apart on my bench and hasn't
been tested in this way. Any suggestions for getting it as clean as
possible?  

Jim Brown  K9YC


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[Gary Hembree]

Jim,
Read the following document, which might help.  There is a spur generated
on 80 meters in some KPA100's caused by a resonance in the TR switch
components.  Easily fixed with a 1K resistor soldered across one of the
inductors.  Won't help 40 meters though.


http://www.elecraft.com/manual/E740035E%20KPA100%20errata%20rev%20C-3.pdf

73
Gary, N7IR
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[Don Wilhelm-3]

Jim,

Gary has a point that I had forgotten about - and yes it can make a
difference on 40 meters too.

Before concluding that this is your problem (although the changes have been
put into new KPA100 kits), take a look at the RF envelope on a 'scope
looking for any evidence of 'modulation' on the CW signal.  It will vary by
band and by the power level - if you see a nice clean RF Envelope, this is
likely not your problem (unless it is too small to observe).

73,
Don W3FPR

> -----Original Message-----
>
> Jim,
> Read the following document, which might help.  There is a spur generated
> on 80 meters in some KPA100's caused by a resonance in the TR switch
> components.  Easily fixed with a 1K resistor soldered across one of the
> inductors.  Won't help 40 meters though.
>
>
> http://www.elecraft.com/manual/E740035E%20KPA100%20errata%20rev%20C-3.pdf
>
> 73
> Gary, N7IR
>

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[Jim Brown-10]

Thanks for all the ideas, guys. I hope to get into the KPA100
tomorrow.

Jim

On Thu, 14 Apr 2005 14:58:46 -0700 (MST), Gary Hembree wrote:

>Some additional thoughts on your problem.



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