[RFI] Powerful RFI

Gary Smith Gary at doctorgary.net
Fri Oct 10 01:50:38 EDT 2008


O'course it's always bad RFI but I'm stumped on this one (and I used 
to think the dog fence down the street was the issue...

Here goes; I live at the last house on a dead end with 1 mile worth 
of trees to the north, 3/4 mile of trees and ocean to the East, 2 
miles of trees and ocean to the west with a small airport about three 
miles away. And there is the street leading in a straight line to my 

Pristine, eh? Problem is there is an electric train Amtrak uses that 
passes by frequently (there are 12' high Hurricane fences on both 
sides of the track so hikers from one state park crossing the tracks 
to the other won't get hit by the "silent" train. In addition, there 
are power lines (not the really big ones) that intersect at the 
corner of my 2 acre lot. But these are lines that carry the power to 
a nearby island so they are not the normal residential variety. 

When it's quiet here radio wise, it's what you would expect and the 
only bugger was 8 houses away there is a hidden dog fence that 
splatters in the 160 meter range.

Recently though something new has happened RFI wise at this QTH and 
I'm pretty stymied as to what it is & what to do about it or who even 
to complain to; the sound can be heard on the links I have provided 


The sound is intermittent but frequent. I asked my father to use his 
icom with a scope to see what he could see and it is detectable from 
the 1.6Mhz broadcast band through 18Mhz with the worst being around 
7Mhz. Perfectly regular pulses. 

I thought perhaps it was from something in the line so I disconnected 
the antenna but the interference stopped. I set up a remote receiving 
antenna alongside the salt marsh but the sound comes in just as 
strong on that as it does on my Butternut Vertical, as it does the 
Inverted V for 80M & 40M. It registers a solid S20 on 40M and S6 on 
80M but it is always the loudest sound I can hear and the noise 
blanker in the Corsair does only a fair job of removing it. The Omni 
V has a poor noise blanker.

Can't imagine it will help much but here's an overhead of the house 
from Google Earth http://doctorgary.net/QTH.jpg

Finally I decided to run the remote antenna (small receiving loop) to 
the corsair & via battery so there is no connection of any kind to 
this gear and yes, the problem was the same on battery & an antenna 
300' from the house.

So tonight I got tired of hearing it and started writing down the 
times it started & stopped. I only did this for a half hour but I 
discovered the RFI is almost always 38 seconds long and tapers off 
and stops in about three seconds. For awhile it was coming almost 
every 2 minutes but around 11PM it became less frequent, being two 
times over the space of a half hour. I have noticed that the 
interference is less in the late evening but this was the first time 
I tried putting times to the occurrances.

So those two recordings, they're the same for all practical purposes 
only they were separated by two minutes.

Any ideas?


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