[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 homeowner’s 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 ham’s fault, because the 
homeowner has no problems until the ham transmits. But it is not the ham to 
blame—it is the homeowner’s 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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