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[RFI] RFI Troubles

To: <rfi@contesting.com>
Subject: [RFI] RFI Troubles
From: Ed - K0iL <k0il@arrl.net> (Ed - K0iL)
Date: Sat, 23 Dec 2000 11:03:48 -0600
On Friday, 22 December, 2000 4:27 PM, gm@netsync.net  wrote:
> I live in an
> apartment that is part of a large house. There is one other apartment
> here too, and my neighbor there has been complaing about RFI from my HF
> rig. His main complaint is that I'm coming through the speakers on his
> computer. My main antenna is a Butternut HF5B 2 el mini-yagi that is
> mounted up on the roof. The bottom of the antenna is roughly 15 to 20
> feet above his computer, and 5 feet away horizontally.

> My first question is: In the eyes of the FCC, is my antenna too close to
> his apartment? I have heard some people say that the FCC expects a ham's
> antenna to be at least 50 feet away from any neighbors, otherwise the
> ham can be blamed for interference. Is there any truth to this? I
> normally run 100 watts output, and I know that my neighbor's apartment
> is within the FCC's RF saftey limits. I occasionally run 500 watts for
> DX pile-ups, which is also within limits, but I only do it when the
> neighbor is out. It's very possible that the FCC will be coming here to
> look at the problem, so I need to know if my antenna is too close (at
> 100w), and if I could be held responsible for the RFI problem.

Ed-W1RFI might've missed one thing I believe:  Given this configuration, 
you may be running enough power to put you OVER the new RF-exposure limits 
for the general public (as opposed to what a ham can be knowingly exposed 
to) on certain bands (like 10 meters).  You should probably determine what 
the maximum power level that you can run on each band with your current 
station configuration.  Here's a couple of web sites to visit for more info 
on RF Exposure:

Hams are now required to meet these regulations even though there is no 
scientific basis for them at this time.  You still must meet the 
requirements no matter what they're based on.

> As for cleaning up the RFI, I have not been able to do much since my
> neighbor is not very cooperative.

The FCC usually comes down on the Ham's side in these cases.  Remember I 
said "usually".

> The problem is from HF fundamental
> frequencies. I'm coming through the speakers on his computer, which he
> insists on leaving on 24 hours a day. He won't turn off his amplified
> speakers - not even before going to bed at night. He uses rabbit ears
> for a TV antenna, and we are in a fringe reception area. His TV is at
> least 30 feet from my antenna, and I clobber every channel. He also says
> I come in through the phone line.

What do you mean "clobber every channel" on the TV?  Video or audio only? 
 Or both?  They are cured in different ways and different locations in the 
TV set.

> Since his main complaint is with the computer speakers, that is where I
> have been trying to help him so far. I don't seem to cause any
> interference at all on his monitor. I tried using ferrite beads on
> various speaker cables and mananged to reduce the interfence by maybe
> 50%, but it is still very noticeable. I only had 2 beads, so I couldn't
> do as much as I wanted, but I doubt that beads alone would have done the
> job. He has a total of 5 speakers, with 2 separate ampifiers. At one
> point I grabbed a hand-full of the speaker wires and the interferece
> dropped WAY down.

Sometimes just cleaning up the rat's nest of wires takes care of alot of 
RFI problems.  All wiring should be only as long as needed.  Excess 
cables/wires should be folded in on themselves to shorten up and eliminate 
all excess wiring.  Use wire ties or trash bag ties to secure the folded 

> I'm thinking I might be able to wrap several turns of
> wire around these cables, then ground the wire to simulate the same
> thing. Does that make any sense?

No.  I don't think you ground the wire without risking damage to the 
devices or at least making them malfunction.  Just shortening up the 
cabling is all that is really needed.

> For the phone line, I will try a bead or a torroid core. For the TV,
> I'll try a high-pass filter, but I have doubts that it will help much.

If it's audio rectification only, a HP filter probably won't much at all. 
 If it's video RFI, it probably will help.  It won't hurt either way, but 
the neighbor should be the one buying these and installing them.  If he 
refuses, the FCC won't even bother talking with him any further or 
bothering you. (Hopefully!)

My biggest concern for you right now is that the FCC may shut you down on 
certain bands over RF exposure concerns.  Look into this area first since 
you are required by law to be in compliance with the new regulations.  For 
example, I no longer use my ground mount antenna on ten meters at any power 
since it is too close to a neighbor's house.  Then again, my roof mount 
vertical is way better on ten anyway and it's on my house so I can run more 
power.  In your case though, the neighbor lives just under the roof mounted 
antenna.  I don't really know how the FCC will view this situation!

Good luck Gerry, & check back with the list with any results, updates or 
further questions.  Happy Holidays!

de ed -K0iL

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