Hi Peter,
There are many ways in which noise enters our radios. Failure to do
proper grounding and bonding both within our stations and throughout our
homes is one cause. Failure to chase down and remove the dozens of noise
sources in typical US homes is another.
There are detailed Applications Notes on my website explaining how RFI
happens, how to chase and hopefully kill it, and how to do that bonding
and grounding. Your symptoms suggest that grounding and bonding is an
important part of your problem, but so is killing as many of those
sources as possible. While line noise is certainly a problem for many of
us, trash generated by electronics in our own homes and those of our
neighbors has long been an equally dominant source of that noise.
k9yc.com/publish.htm
k9yc.com/RFI-Ham.pdf
http://k9yc.com/KillingReceiveNoise.pdf
http://k9yc.com/GroundingAndAudio.pdf
Don't let the title of the last link fool you -- it's mainly about
grounding and bonding for lightning safety and to kill noise.
73, Jim K9YC
On 2/1/2024 6:38 PM, Peter Dougherty (W2IRT) via Elecraft wrote:
I have been experiencing extreme powerline noise for years (this isn't about
that), so I've been looking for ways of mitigating it on my end to at least
get useful signals of some kind on 80 and 160. I have a K9AY loop RX antenna
and a full-size 80m Inverted Vee at 65'. Tonight, I was switching between my
Inverted Vee and the K9AY loop with an external noise-canceller (WIMO "QRM
Eliminator") in line. It's somewhat effective with about a 30dB improvement
on the K9AY. But then something quite unexpected happened.
I wanted to see how low my noise floor was with this new device inline so I
figured I'd switch to an empty antenna port (ANT-2 on the K3s). As soon as I
pressed the button my noise floor dropped to from about -130 to -140 on my
P3, lower than it's been in years. But I was still hearing FT8 and the
signal-to-noise improved considerably. This is.surprising to say the least.
How am I still able to copy weak FT8 signals (and CW) with absolutely
nothing connected to the ANT-2 port? I'm talking about copying stations in
A7, V3, CT3, and west-coast US, not strong locals. I don't think I've ever
had lowband S/N that good before to be honest. What is the port isolation
supposed to be like on the K3s and is what I'm seeing normal?
Just to be clear, I disconnected my AUX antenna that I use occasionally for
diversity RX, and my K9AY and it was still the same. Only my Inverted Vee
was connected to the K3s. When I disconnected it everything dropped to
nothing. Is what I'm seeing expected behaviour? And this leads to a big
question. With ANT-2 selected for RX, (remember, there's nothing connected
to the ANT-2 SO-239 on the radio) is it possible to select a different TX
Antenna? I'd be pleased as punch to receive in this configuration but it's
not practical to manually switch from ANT-2 on receive back to ANT-1 for
transmit.
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