[RFI] 160 Meter Interference

[Tom Rauch]

The 90kHz spacing and reasonably clean carrier is a dead
giveaway. 90 kHz is in the most common range of low or
medium power switching power supplies. The carrier was
basically clean except for minor ripple. It had very little
frequency wobble caused by changing data or a changing load.

While it certainly could be from a power supply in a digital
device, it almost certainly would be from the power supply
section. It very clearly had all the characteristics of a
power supply with a steady load, which means it could be
anything from electric lights to battery chargers to line
operated consumer devices of any type.

Best way to find it is to drive and listen, and watch the S
meter.

I found a computer over a mile away (airline) that had a
devastating SMPS backfeeding the power line in differential
with the modem connection to the telco line. It was S9 +15dB
at my house compared to an S1 background noise here, which
in more meaningful terms (since my S meter like nearly all S
meters is not 6dB per S unit) was about 40dB out of my noise
floor. The actual conducted path via driving along the wire
was nearly three miles, so this crap can go a long distance
and be strong!

73, Tom W8JI