To me, it sounds like that when the ATU is inline (& I presume you let
it tune to that antenna at some point. Yes/No?)
The antenna is better matched to the transmission line, so more of the
on-air "ambient" noise is delivered to the RX.
I get the same here, where 60m is quite noisy anyway. At times over
some 10dB difference! Even more noticeable on 80m and 160m. Where the
"bare" antenna (random wire sloper) is naturally even more inefficient.
Do you have a passive/manual ATU you could compare with, using the same
RX and Antenna?
If it was SMPS noise, I'd expect (in your case) a 60 or 120Hz based buzz
to be part of that "noise". But I don't hear that.
73.
Dave G0WBX.
On 03/12/2023 15:52, elecraft-requ...@mailman.qth.net wrote:
Subject: [Elecraft] Noise from KAT500?
--
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