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Author Topic: Need Help to Identify RFI Source - 7 to 24 mHz  (Read 755 times)
W9EAA
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Posts: 2




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« on: February 29, 2008, 09:14:15 AM »

I first became aware of this on the 20m band. On my Icom 756 Pro III screen it shows up as a spike, about 10 to 20 dB higher than a background S4 noise level. The spike is about 1.7 Khz wide and is occurs exactly every 19.4 KHz, between approx 7 MHz and 24 MHz. The audio, when put through my sound card, shows up on a WinPSK waterfall as a series of sub-spikes about 100 Hz apart.

The base frequency of any spike drifts up and down at a very slow rate.

It's continuous and does not seem to go off during the day or late at night.

I have a vertical antenna and am in a suburban location.

Does anyone know what causes this particular RFI ?

W9EAA
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N2RRA
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« Reply #1 on: March 03, 2008, 06:06:01 PM »

I have experienced this, and found the computer monitor to be the culprit.

Have you tried turning off the monitor if you have one on near the radio?

Turn on and off electronic devices with any kind of power supply,transformers, or lighting with florescent bulbs could be the RFI source.

If you don't have your equipment on a dedicated outlet try doing so. If your using an existing outlet walk around, and make a list of devices that are on the shared outlet. Then go around unplugging each device to rule out source of RFI.

This would be a good start!

73!



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K3AN
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Posts: 787




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« Reply #2 on: March 09, 2008, 08:11:27 AM »

If possible, run the radio off a 12 Volt battery. It doesn't need to be a high-capacity battery since you're only going to be receiving and only for a few minutes. Then turn off the house's main circuit breaker. If the RF noise is still there it's coming from somewhere outside your house. If it went away then it's coming from inside, and you can try finding it as described above.
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AA5CH
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« Reply #3 on: March 09, 2008, 07:25:51 PM »

Got an HP printer in the house?

If so, unplug it and see what happens to your RFI.

I've had trouble with two different model HP printers -- specifically their power supplies.

Try unplugging any "wall wart" power supplies you have. They can cause RFI similar to what you are describing.

73,

Brad
AA5CH
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W9EAA
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Posts: 2




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« Reply #4 on: March 15, 2008, 01:51:30 PM »

The source is not coming from the home.  Turned off all breakers and the spikes remain.  The same noise is heard on my backup radio, a TS-940SAT.  Looking for additional ideas.  I may have to build a small shielded loop and find a portable rig/radio.

W9EAA
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KJ3P
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Posts: 1




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« Reply #5 on: March 16, 2008, 03:06:16 AM »

Had the same problem here in the Philadelphia 'burbs. Same spikes, same frequency interval. Culprit was a cable company's pole-mounted power supply which seemed to use the power lines as an antenna. Tracked down by roaming around with xcvr temporarily installed in vehicle. Cable company (Comcast) was actually quite helpful after a stern letter to their customer service dept citing FCC rules re: incidental radiators and "egress" (which it was not, but this is a term they understand).

My theory: a poorly filtered or defective switching power supply...the 19.4 kHz freq is about right I think. They swapped it out and the problem went away.

 --Jim KJ3P
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N8DV
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Posts: 60




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« Reply #6 on: April 27, 2008, 08:49:37 AM »

Please read my new post about RFI from florescent "energy-saving" light bulbs. Do you have any in your home and are they on when you operate?
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