[RFI] 144 MHz Interference Source

Cortland Richmond ka5s at earthlink.net
Wed Oct 1 21:20:24 EDT 2003

144 MHz plus or minus is pretty common, as a lot of devices -- even pretty
rudimentary stuff, nowadays -- uses 4, 8 or 16 MHz clocks, and current
technology is built around fast devices. Could be something as innocuous as
a telephone answering machine or even a plain old (digitally clocked)
telephone. Could be a computer or an answering machine, a router or a CD
player. Could be nearby telecom equipment. But simple stuff is likely to be
built with less regard for EMI. They don't waste effort on a multilayer PWB
for something that costs only three dollars to make, do they?  Or even slew
rate reducing series resistors!

You might look for higher order harmonics to help localize this. 


> [Original Message]
> From: Jim Brown <jimbrown.enteract at rcn.com>
> My first post is a question about an interference source that I'm
> hearing at the low end of 2 meters and just below it. The carrier
> frequency appears to be about 143.995 MHz, with periodically spaced
> sidebands extending above the carrier for at least 100 kHz into the 2 m
> band.  I can hear this source both with the FT100D and with my TH6
> handheld, and it appears to be fairly local to my QTH. It dies out
> pretty quickly when more than about 400 ft away. Principal sidebands
> seem to be at roughly 3 kHz spacings, and all sound like carriers. 

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