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Author Topic: RFI question  (Read 2893 times)
KA4NMA
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Posts: 320




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« on: June 14, 2013, 07:01:56 PM »

I live in an antenna restricted apartment.  I installed a loop around the ceiling of my shack. I ran it to a SGC 327 Tuner.  Friday, I tuned up on 10m, heard nothing, then 17m, then 20m all tuned up and hearing nothing.  So I tried 40m. 2 circuit breakers tripped.  One was a GFI circuit breaker.  Any idea why they tripped on 40m and not the other bands?

Randy ka4nma
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AA4PB
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Posts: 12770




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« Reply #1 on: June 14, 2013, 07:08:57 PM »

Power wiring acts as an antenna to pick up your RF and transfer it to the breakers. The wiring is probably closer to resonance on 40M than it is on other bands.
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WX7G
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« Reply #2 on: June 17, 2013, 06:16:45 AM »

The quick fix is to reduce transmitter power to where the breakers do not trip.

If the GFI breaker is a wall socket it can be easily replaced. The newer GFI sockets tend to be more RF immune.
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WB2EOD
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Posts: 218




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« Reply #3 on: June 17, 2013, 07:25:04 AM »

I agree with both AA4PB and KA4NMA. 

With regard to the GFCI breaker, it is likely that a piece of house wiring is resonant at 40 meters.
Older GFCI breakers are notoriously sensitive to RF.  Newer ones less so.  I had the same problem and solved it by replacing the GFCI outlet.  If you go this route use a good reputable brand.  Pass and Seymour seems to work.

With regard to tripping the Non-GFCI breaker, I suppose it may be possible, but I never heard of an ordinary breaker tripping out on RF. 

Operating with an indoor antenna can be tricky.  You are too close to the antenna and strong RF can do some strange things, particularly if you are in the same room.  Assuming you can't get further away from the antenna, you will probably have to reduce power and hope for better band conditions

Hope this helps
73
WB2EOD
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AA4PB
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« Reply #4 on: June 17, 2013, 07:40:57 AM »

With regard to tripping the Non-GFCI breaker, I suppose it may be possible, but I never heard of an ordinary breaker tripping out on RF. 
Hope this helps

1) If it's a newer home it could be an arc-fault breaker. They contain electronics that could be sensitive to RF.

2) Something powered by that circuit could be sensitive to RF and overloading the circuit.
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NK7Z
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Posts: 753


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« Reply #5 on: June 17, 2013, 09:13:20 AM »

I agree with both AA4PB and KA4NMA.  

With regard to the GFCI breaker, it is likely that a piece of house wiring is resonant at 40 meters.
Older GFCI breakers are notoriously sensitive to RF.  Newer ones less so.  I had the same problem and solved it by replacing the GFCI outlet.  If you go this route use a good reputable brand.  Pass and Seymour seems to work.

With regard to tripping the Non-GFCI breaker, I suppose it may be possible, but I never heard of an ordinary breaker tripping out on RF.  

Operating with an indoor antenna can be tricky.  You are too close to the antenna and strong RF can do some strange things, particularly if you are in the same room.  Assuming you can't get further away from the antenna, you will probably have to reduce power and hope for better band conditions

Hope this helps
73
WB2EOD

You should do your RF Exposure calculations as well...  If you have an upstairs neighbor, you are probably exceeding the FCC limits for exposure...  To say nothing of yourself...  See:
http://hintlink.com/power_density.htm
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Thanks,
Dave
For reviews and setups see: http://www.nk7z.net
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