[RFI] A Bizzare EMI Story

[donovanf at starpower.net]

From: "Sam Josuweit" <samjos at epix.net> 
To: topband at contesting.com 
Sent: Wednesday, November 7, 2018 2:15:35 AM 
Subject: Topband: Bizzare EMI Story 

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)