I'd suggest that you, or your neighbors may have a solar power system,
inverter, batteries that might be the culprit. Solar power is ubiquitous
now and not all of the associated equipment operates cleanly. I made
careful measurements before and after my solar install. While my system
has proven to be fairly clean, I did notice some odd birdies once the
install was complete. Fortunately, none of them has affected my Ham Band
reception. It does show up on the spectrum analyzer. If the solar isn't
on you property, but on adjoining property, your beam headings will show
approximate direction. You may have to attenuate the antennas is you are
looking and seeing level differences in order to refine your search. A
portable AM radio with a loop stick antenna can be helpful once you've
come closer to isolating the possible offender. If you find it to be a
solar system, conventional choking devices, ferrite beads, etc can help.
73
Chuck, W6AJW
On 01/02/2021 18:32, Ignacy Misztal wrote:
Thank you for many useful directions.
As my noise is usually cancelled completely by a noise blanker,
this suggests a powerline noise. The noise persists with the local power
off so it is not generated locally. There are no neighbors close.
The noise varies in amplitude. For example, on one beam, the noise peaks at
21.2 MHz and is 10 db weaker at 200 KHz away. On another beam 100ft away,
the noise peaks at 21.0 MHz and is also 10 db weaker at 200 KHz away. The
noise is also present on 10m but is relatively weaker on 20m. So it seems:
1. The noise is originating from one location because otherwise NB
would not be able to blanket it.
2. The noise is radiated from several points, creating nulls and peaks
around.
I don't know why the noise is 24h/day, unlike a typical powerline noise,
and why VHF readings are weak.
For RFI detection I have MFJ 3 el sniffer, 80m RDF radio, a magnetic loop
tuned 20-10m that is connected to KX3, and an ultrasonic sniffer. Also
tried a 10 el 2m beam connected to FT991, for greater directionality.
Ignacy, NO9E
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