[Johnson] RFI
Richard Peterson
wb5nen at hotmail.com
Thu Jun 21 13:37:32 EDT 2007
Welcome to the world of neighbors and RFI. There are lots of explanations
out there, and lots of bad information. I mean LOTS of band information. For
example, I always chuckle when someone says it can be cured with a balun
because feedline radiation is causing it when after all, most of the power
is being radiated by the antenna! (And if not, you really do have
problems.)
The stories go on.
I have caused the problem you describe. I have also caused motion detector
lights to flash as I speak. I have gotten into intercoms, stereos and
telephones. I have had a lawyer across the street threaten to sue. And on,
and on.
In each case, the homeowners unit in question was improperly acting as a
radio receiver and nothing could be done on my end short of changing the
laws of physics. In each case, the placement of chokes on the affected
device easily cured the problem
chokes on speaker leads; chokes on
telephones; chokes on the power going to the motion sensor light; chokes on
long leads going to intrusion alarms. But it does take cooperation with the
homeowner.
Naturally, the homeowner presumes it is the hams fault, because the
homeowner has no problems until the ham transmits. But it is not the ham to
blameit is the homeowners equipment. At least, that has been my experience
over 30 years of dealing with it.
Consider the attorney across the street who was going to sue he had
65-feet of wire going to a left channel, and 65-feet going to a right
channel. Any wonder he heard me when I operated on 75 phone? His stereo was
sitting in the middle of a dipole antenna. And I was blasting into his
living room Little chokes on the speaker leads totally cured it. He and I
had a cold beer.
The ARRL has some excellent literature on this available. Please read up on
it. Beware the voodoo.
Richard
WB5NEN
owbugs at piobaire.mines.uidaho.edu>,<hallicrafters at mailman.qth.net>,
<johnson at mailman.qth.net>
>Subject: [Johnson] RFI
>Date: Thu, 21 Jun 2007 11:18:21 -0500
>
>Hello everyone,
>
>
>
>I got on 75M AM last night testing out a new antenna (multi-band trap
>inverted vee for 80/40/20 I picked up at HamCom). No AM activity that I
>could hear at 3880 so I dropped down to about 3875 and broke in on a SSB
>group. The antenna seemed to be working fine.
>
>
>
>Then, the XYL appeared in the shack holding the phone. Seems our next
>door neighbor was calling complaining that I was causing their security
>system to go off.
>
>
>
>I was transmitting using a B&W 5100B barefoot at about 90 watts output.
>This rig has a built-in low pass filter. No tuner was in the line. The
>rig loaded up fine. The antenna is fed with coax.
>
>
>
>This is a new one on me. Anyone ever have trouble with RFI getting into
>a security system wreaking havoc? Any suggested fixes or
>trouble-shooting I could do?
>
>
>
>For the hallicrafters list, I was receiving on an SX-101A.
>
>
>
>For the Johnson list, my Viking II is about ready for an on-air test.
>
>
>
>Thanks in advance for any help.
>
>
>
>Mike Langston KL7CD
>
>Dallas-Ft. Worth
>
>Johnson mailing list
>Home: http://mailman.qth.net/mailman/listinfo/johnson
>Help: http://mailman.qth.net/mmfaq.html
>Post: mailto:Johnson at mailman.qth.net
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