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Infrastructure RFI

RFI caused by faulty Cable emergency backup power supply:

Cable Company RFI

Cable Company RFI

Cable company power supply

Cable company power supply

This turned out to be a power supply from the cable company. The unit was actually made by Alpha Technologies and it keeps the cable system “hot” during electrical outages. It was very irregular and identified via one-second “ticks” and about every two-minutes the frequency would shift for about 15-seconds and then shift again and the one-second ticks would return. I don’t know the native frequency as it “repeated” every 93 KHZ through wide swaths of the HF spectrum.  Credit Alpha Technologies with eventually replacing this XM-2 Inverter Module with a “quieter” one.

RFI caused by an Electric Fence:

RFI Caused by Electric Fence

The popping you hear is the RFI created by an electric fence as it triggers the High Voltage pulse.  If you watch the P3 you will see just how strong a signal it is…  Pretty much all electric fences sound like this, a single pulse with some time then another single pulse.  Most fences have about a 1-5 second pause between pulses.

Here is the same fence, as viewed on an Icom 7300:

Electric Fence RFI, as seen on an Icom 7300

RFI caused by an Electric Blanket:

Grow Light and Electric Blanket

Grow Light and Electric Blanket, click to enlarge.

The horizontal lines are from an electric blanket about 50 feet from the antenna.  The vertical lines are a grow light operation about a block away.  All on 80 meters.

RFI caused by Ionosonde:

RFI from Grow Light one block away on 80.

RFI from Ionosonde.  Click to enlarge.

The sloping line is the Ionosonde as it moves across 40 meters.  It will manifest itself an a single event woop, when you listen to it using USB/LSB.

RFI caused by under shelf Halogen lights:

RFI: Lights off

RFI: Lights off

RFI: Lights on

RFI: Lights on

Transformer causing RFI.

Transformer causing RFI.

The antenna was about 30 feet from the lights.

RFI caused by defective lightning arrestor on a 7200 volt line:

RFI caused by a Faulty lightning arrester

RFI caused by a Faulty lightning arrester

The antenna was about 2000 feet from source.  It would look like this no matter what the bandwidth of the P3 was set for on 20 meters.

RFI caused by the Cyprus Over the horizon radar on 17 Meters:

(Note: Javascript must be enabled to see movie)

RFI from Cyprus OTH Radar on 17 Meters

RFI caused by the Cyprus Over the horizon radar on 15 Meters:

RFI caused by Cyprus OTH Radar on 15 Meters

RFI caused by Battery Charger:


RFI caused by Invisible Fence:

RFI caused by an Invisible Fence

RFI caused by an Invisible Fence as viewed by an SDR.

AM mode, 3 KHz bandwidth.

WFCO, trailer power distribution center RFI:

WFCO RV Distribution Center

WFCO RV Distribution Center


Many thanks to N2KI for taking the time to create this presentation, and allow its use here…

Back to sources…

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William Manser
3 years ago

i have a constant qrm on 40M. on a icom 7300 waterfall display it appears as 3 vertical sine waves. i have seen nothing like this in 60 years of hamming. i would like to send a short video/ audio clip for description. can i submit this? to what e-mail address? thank you; 73; bill WA6SZE