[TowerTalk] RFI resolution

Mon Sep 29 12:10:38 EDT 2003

Jim:

Several years ago at the request of the Dallas FCC Field Office I headed
a team of Dallas/Fort Worth hams who participated in a neighborhood RFI
problem investigation reportedly involving a ham in Fort Worth.  At the
time I knew the tech rep. for the local tv cable company (who no longer
works there), but he was very helpful and joined out "team".

According to Sandra Morris of the Dallas FCC Field Office, this
neighborhood had all kinds of problems from RFI, cable, phone, etc.

The team I assembled included hams who worked for the cable company,
Lockheed's avionics department, Southwestern Bell Telephone, and other
electronic sources.  I was the non technical person hi hi since my job
was to just assemble the team and write up a report for the Dallas FCC
on our findings.  One of the guys has a spectrum analyzer and the guys
from Lockheed brought some of their test equipment too. It took us 4-5
hours to survey the entire neighborhood.

We had the local ham's cooperation who knew in advance we were
coming--along with that of the neighbors-- the Dallas FCC office told
him it was either cooperate voluntarily with us or they would send a
couple of their field office people over.  In one house the cable person
and I went to, we found he was using a TV coax distribution amp from
Radio Shack, that overloaded his cable reception like crazy even without
the neighborhood ham being on the air.  It was interesting, when the two
people from the cable company disconnected the distribution amp (I think
it boosted the signal something like 20 db or so, but that was several
years ago) the resident received a "better" television photo than with
it and no interference from the ham either on 10-80m.  

At a little old lady's home who had one of those life call systems that
calls for help if she presses a button on a remote control she carried,
we found a jungle of telephone wire.  Every time he keyed up, it set off
the woman's life call system.

It seems she had just one phone jack in the entire house, but she fed it
with at least 200+ feet of phone extension wiring that snaked all over
the floor, split off at least two or three times, and all of it probably
totaled the same length as a full size 80m dipole.  Once she agreed to
only one short phone line, the problem stopped.

The ham wasn't without fault either.  We found his "station ground" was
about 75 ft. of coiled up wire leading from the hf rig to an 8 ft.
ground rod driven only partially into the ground, not even halfway.  The
field office folks as they suspicioned he was using an amp (not that
that was a violation), but we never found one, although there was a
"vacant" area about the size of an SB220  between his rig and other
equipment.

Once we left and I made my report of our findings, a follow-up call to
the Dallas FCC field office weeks later indicated that things seemed
peaceful in that neighborhood.

Tom, WW5L

Jim Miller wrote:
> 
> I am wondering if there is a separate "amp" for the subwoofer that is
> picking up the signal and it could be grounded or shielded.  I had a preamp
> for the cable TV to boost the signal for 5 TV connections and it was
> terrible, picked up everything.  That's how I found out there was a ham just
> a block away from me and this was before I was a ham.  Sometimes coiling
> extra cable to make an inductor at the speaker helps too, but I would
> suspect it is being picked up by an amp or preamp for the speaker.
> 
> Just an opinion from a non-expert and possibly something to think about.
> 
> 73, Jim
> 
> ----- Original Message -----
> From: "David Cook" <davec at netdave.com>
> To: "TowerTalk Discussion Group (E-mail)" <towertalk at contesting.com>
> Sent: Saturday, September 27, 2003 12:49 AM
> Subject: [TowerTalk] RFI resolution
> 
> This may be a bit off topic for the TT group, my apologies if so. Please let
> me know where the most appropriate forum for this question would be.
> 
> I've got a problem with RFI'ing one of my neighbors. Everyone else in my
> neighborhood has been very cooperative and I've been able to resolve the
> problems with all them. But one neighbor has a bad RFI problem when I point
> my beam to Australia, which is directly towards her house. I've asked her to
> give me a call when it would be convenient to do some testing to try to
> determine the problem, but she won't call me back. It's only when I do a
> test CQ when the band is in that she immediately calls me and starts
> complaining about the RFI on her sub-woofer.
> 
> I suspect that I can solve the problem easily with filtering or simple
> toroids on the sub-woofer cables, but she a) doesn't want me to come in her
> house and mess with her gear, and b) won't even call me back to talk about
> it when we might have time during the day to work out our problems.
> 
> Has anyone had any difficulties in dealing with this kind of a situation?
> What should I do?
> 
> Thanks for any advice, and 73,
> -- Dave, WAØTTN
> 
> _______________________________________________
> 
> See: http://www.mscomputer.com  for "Self Supporting Towers", "Wireless
> Weather Stations", and lot's more.  Call Toll Free, 1-800-333-9041 with any
> questions and ask for Sherman, W2FLA.
> 
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> _______________________________________________
> 
> See: http://www.mscomputer.com  for "Self Supporting Towers", "Wireless Weather Stations", and lot's more.  Call Toll Free, 1-800-333-9041 with any questions and ask for Sherman, W2FLA.
> 
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