[Elecraft] KPA-100 spur on 160M?

[Tom Althoff]

Hi Ron!   It was a Jan 2004 production release that was unbuilt when I
bought it 2 weeks ago.  Elecraft was kind enough to ship me the new shield,
firmware and upgrade mods to bring it up to spec so it's up to snuff
including the mu-metal speaker shield.

I received a very interesting e-mail from Ron ZL1TW with a possible fix that
corrected a spur he had on 80 and may have had on 160 as well.  If it works
I'll repost it to the group.   I'll put it in today when I get home from
work and report back if successful.

73 de Tom K2TA

----- Original Message ----- 
From: "Ron D'Eau Claire" <rondec at easystreet.com>
To: "'Elecraft'" <elecraft at mailman.qth.net>
Sent: Tuesday, November 30, 2004 10:35 AM
Subject: RE: [Elecraft] KPA-100 spur on 160M?


Tom, K2TA wrote:
Has anyone who experienced oscillation with their KPA-100 (internally or
externally mounted) seen a spur about 1Khz up from the main signal?

If I crank up my power to 100W a very "brrrrrippy" spur pops up just above
my signal only on 160M.   If I keep the power at 95W or less it is not
there.

-----------------------------------
How "old" is the amp, Tom? There have been a couple of shield upgrades that
have to do with stability issues. I've never noticed a problem with mine, so
I'm not certain of the exact symptoms. One "upgrade" added a new shield with
side clips that better grounds the shield to the case on the edges. A second
one adds a lower-inductance ground to the shield right at the SO-239 output
connector using two ground lugs, one under one of the connector screws
replacing the lock washer there and the other under the closest shield
screw. The two ground lugs are soldered together to form a "strap" from the
connector ground screw to the shield mounting screw.

Ron AC7AC


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