Dear RFI-hackers:
I have been experiencing QRM from some unknown source for the past
several months, a picture of it is here:
<http://rkrishnan.org/files/40m-qrm.png>
This happens in every band and is repeats at 20khz. The signal is steady
and not wobbly like one sometimes see in SMPS created QRM. When
listening to SSB, I turn on the notch filter function on the SDR to get
rid of the "carrier" like signal. But that only does a bit.
I have tried turning off the mains and hunting for it inside the house.
I live in a densely populated area. All the houses use power inverters
as power disruption is quite common in this part of the world. I have
tried powering the house directly bypassing the inverter to rule out
whether it is coming from my own inverter. But so far, I haven't been
able to find the source for it within my house. If anyone has seen such
an RFI signature and can give me some clues about what it is, I can try
to hunt for it in the neighbourhood. I see it all the time, 24 hours!
When power goes off in the area, the inverter creates heavy QRM and so
this gets buried in other noise. I am getting a mains filter etc. THis
is coming from the antenna side though (I think), as without the
antenna, I am unable to see this signal (I found other local SMPS
sources that way and eliminated them).
Any help appreciated.
73
Ram VU3RDD
--
Ramakrishnan
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