[Elecraft] Re: magnetic fields and phase noise?

[Earl W Cunningham]

Fraser, G4BJM wrote:

"Interesting Earl, the non exhaustive tests I've done indicate that it is
not due to magnetic fields."
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When I first told Elecraft about this problem, they sent me the new
shield for the KPA100, which didn't help.  Then they sent a mod kit that
had to do with reducing spurious RF, which didn't help.

Then I eliminated the KPA100 as being the culprit by removing it (and
installing the original cover).  Driving the amp (with only the 10 watts
available) resulted in the same problem.  Clean when barefoot (as is the
KPA100).

Then I manually keyed the amp (instead of using the KPA-100's key output)
-- no change in problem.

Then I brought my K2/100 over to a friend's QTH and tried it with his amp
-- same problem.  Separation from his amp was 6 feet.  His amp is an
Alpha 99, mine is an Alpha 76CA (both have hypersil HV transformers).

Then, at my home QTH, I set up the K2/100 in an adjacent room and ran a
coax from it to the amp in the ham shack -- no trace of the problem.

All tests were done on CW, monitoring the transmitted signal on another
receiver (FT-1000MP) using narrow (250 Hz) bandwidth.  The problem sounds
like noise on the sidebands of the transmitted CW signal extending out at
least +/-5 kHz from center freq.  There's no reason to believe that this
problem does not also exist on SSB.
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"But if indeed that is the case, there must be a relatively easy, if
perhaps not elegant, way of significantly improving this."
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It has been suggested that mu-metal shielding might alleviate the
problem.  I'm considering making mu-metal bottom and side covers for my
K2.

Another ham (W4FMS) told me he had the same problem with his K2/100 and
Alpha 87A amp.  He found that placing an aluminum cookie sheet between
the K2 and amp with only 3 feet of separation resolved the problem.

All things point in the direction of a K2 problem that is not phase
noise.

73, de Earl, K6SE