Topband: Bizzare EMI Story

Sam Josuweit samjos at
Tue Nov 6 21:15:35 EST 2018

So after taking a few years off from radio, over the summer I decided to
rebuild my station and antennas and get back on the air. Was doing fine
until a few weeks ago, my noise level was S9 on 80 meters. Using a beverage
it was ok but on my TX antenna it was 120hz hash. I tried everything to
locate the source, unplugged computers, Directv, DSL modem, freezer you name
it, checked my entire ground system, it still was there. To make matters
worse after listening to it on AM I noticed I could hear the local NOAA
Weather radio station, which is on 162.55 MHZ FM! Now the local transmitter
for NOAA is on the next mountain over and line of site with my remote QTH,
but 162MHZ to 3.7MHZ?? This really had me stumped, and I was just about to
give up. I have an old farm house and don't have too many power outlets, but
I realized I missed checking the one in our bedroom, and there sits my NOAA
weather alert radio. Unplugged it and the hash was gone. Since these radios
monitor constantly for alerts, they must just mute the audio when not in
use. Apparently something in the radio power supply failed causing the power
noise, which was then getting modulated by the muted audio. This was
propagating thru my whole electrical system. I'm just glad I found it.
Debating if I should take a look at the weather radio or smash it with a
sledge hammer.


Sam (N3XZ)


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