[ADXA] noise issue - take 2

[EJ Jones]

I’m certainly not an expert of noise, but I had something similar with an SDR receiver. I put a high pass filter on it to block the a.m. band and it got a lot better.   Wish you were a little bit closer and I’d lend you a high pass filter to stick on there and see what happens.
EJ

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________________________________
From: adxa-bounces at mailman.qth.net <adxa-bounces at mailman.qth.net> on behalf of Jussi Eloranta via ADXA <adxa at mailman.qth.net>
Sent: Monday, March 23, 2026 3:45:28 PM
To: 'ADXA' <adxa at mailman.qth.net>
Subject: [ADXA] noise issue - take 2

Hi,

Just recorded the 160m noise on the panadapter. I was expecting it to be
wide and all over the place. However, see attached. Bog is beverage on
ground (wideband resonant) and invL is my inverted L (narrow resonant;
SWR only OK at the bottom of 160m). You can see that both spectra are
surprisingly narrow. They have center around 1.840 MHz (FT8 160m
frequency, of course!) and extend to the sides by about 100 KHz. I was
initially looking at this with my inv L and thought that, OK, that must
be just the antenna response I am seeing. But now that I see the same
thing with the BOG, I am not so sure what to make of this. If I scan
more to the AM band, it seems that it is clear over there but then going
further down in frequency I find another similar spot that is noisy.

So, is this power pole noise after all? And if not, what on earth could
it be? It has the characteristic raspy tone with multiples of 60 Hz in
it. On AM it sounds like the typical power line hum. All that fit power
pole noise but the spectrum does not - I think. Furthermore, I do not
hear this noise at all on 80m. This is not from my shack as I have
turned off power and used the radio on battery power. I do hear
something weak on 6m from far away but I have no idea if this is the
same thing as what I see on 160m.

Jussi (aa6kj)
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