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Author Topic: RFI Help  (Read 390 times)

K8ALM

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RFI Help
« on: March 08, 2021, 08:15:56 AM »

My RFI just started in the past three weeks.  Can one of you gurus give me some hint as to what could cause this type of display pattern on my Icom 7610 spectrum?  When I disconnect both transmit and receive antennas the horizontal lines disappear so it does not appear to be my equipment.  In our housing development all of our cable, phone and electrical lines are buried.  I'm stumped.  Any suggestions are greatly appreciated.

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K6SDW

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Re: RFI Help
« Reply #1 on: March 08, 2021, 08:30:36 AM »

Been there, bought the T-shirt...HI HI. Not enough information, but make sure you have a good earth ground. Also, I can run hf rig on batteries at my QTH thus shut the mains off to see if RFI coming from my QTH. Searching for the culprit it's a process of elimination.

There's so many potential RFI sources, ARRL publishes an excellent book on the subject.

GL
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K8ALM

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Re: RFI Help
« Reply #2 on: March 08, 2021, 08:35:18 AM »

I was trying to post a snapshot but I can't figure out how to do this.
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LA9XNA

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Re: RFI Help
« Reply #3 on: March 08, 2021, 08:38:06 AM »

Start very simple!
Have you got any new electrical equipment installed when the RFI first appeared? If so switch it of and see if the RFI is gone.
Are you able to power your radio form a battery source, if not buy,beg,borrow a battery.
Turn of all your circuits in the house.
Check the bandscope of your radio and see if the RFI is gone. If not its on the outside of your house/electrical installation.
Switch on one circuit at a time while checking the bandscope of your radio. When you find the circuit with RFI unplug everything and check for RFI. start to plug back until the RFI is back and you got your appliance.

There was a post here in the past mentioning something about Pot growing and RFI. I think that the essence was that cheep chinese pallasts for the growing lamps produced RFI. So you should check out the local potheads :-)

Check these two links.
https://interferencetechnology.com/identifying-and-locating-radio-frequency-interference-rfi/
http://www.arrl.org/files/file/RFI/Thompson%20Noise.pdf
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N3WTK

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Re: RFI Help
« Reply #4 on: March 08, 2021, 08:59:00 AM »

I couldn't figure out how to add images here, either, so I've been using https://postimg.cc/ and posting the link.

So, until you get some pics, are you saying that this RFI was not there, you made no changes to your station (antenna, rig, wiring, etc.) and then suddenly this appeared?
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Dave / N3WTK

K8ALM

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Re: RFI Help
« Reply #5 on: March 08, 2021, 09:06:14 AM »

This just started three weeks ago during the CQ 160.  I've added no new equipment.  I think this link should work.

https://i.postimg.cc/NFzrY7m7/20210307-084507.jpg
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W6QW

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Re: RFI Help
« Reply #6 on: March 08, 2021, 09:19:05 AM »

To help assess the root-cause, some more information would be useful:
1. Is the RFI only on 160M?  If not, does the noise level decrease with frequency?  Is the RFI constant across all bands?
2.  A time-domain assessment would be helpful.  You can obtain this by using the audio scope feature of the radio.  Change the mode to AM and measure the waveform pulse-to-pulse interval (assuming it's an arc-fault noise source).  If the intra-pulse time is 8.3mS, then the source is, most likely, a 60Hz spark-gap noise source.

Perhaps, if you can post a time-domain picture for 160M and, say 20M, that would be useful.  That waveform will help delineate the source possibilities.

(disclaimer - I don't own the IC7610 so I am assuming it has an audio-scope feature).

« Last Edit: March 08, 2021, 09:39:57 AM by W6QW »
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K8ALM

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Re: RFI Help
« Reply #7 on: March 08, 2021, 09:54:02 AM »

The IC-7610 has an audio scope but I'm not sure how to take measurements.  Let me do some research on this.
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WB8VLC

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Re: RFI Help
« Reply #8 on: March 08, 2021, 10:17:47 AM »

It sounds like What you need is a good ice storm to take out the poor electrical grid and piss poor failing infrastructure in this country.

After our big Oregon ice storm that had power off for close to 2 weeks along with having over 1000 miles of new lines and crappy cobbled together connections and jumpers which were replaced along with thousands of transformers replaced, hams all over northwest Oregon and southwest Washington  have been reporting the best HF listening experience in decades.

I made numerous measurements of how poor RF operation was just due to RFI noise issues for the past 10 years and then during the ice storm/power outage I was operating from a battery and having the wonderful experience of only a pleasant s2 noise level.

Best of all was that when our power was restored 9 days later I was still experiencing the low s1 to s2 noise level.

Prior to the big ice storm my HF noise on all bands  was s7 to S9 plus making HF very tiring and not enjoyable at all.

For the past 2 weeks I have been I firing up all my antennas listening from 160 up to 10 meters and this is the most enjoyable listening experience that I have had since the late 1980's.

I was just on 20 this morning listening with a simple 20 meter loop to N7DD in Tucson chatting with a DL station in Germany along with a PA station in the Netherlands and most enjoyable of all was hearing Saif, A71AM in Quatar, with a s5 to s6 signal all the while with only a s1 background noise level.

« Last Edit: March 08, 2021, 10:21:13 AM by WB8VLC »
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KB5ZSM

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Re: RFI Help
« Reply #9 on: March 08, 2021, 10:52:43 AM »

Sometimes something as simple as a portable AM broadcast receiver can be used to quickly locate the offensive signal. FOX HUNT!!!
73s,
Win KB5ZSM
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W1VT

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Re: RFI Help
« Reply #10 on: March 08, 2021, 11:29:50 AM »

Yes, these days direction finding is what you need to locate something once we rule out power line noise.
Selectively shutting off the power would also work but I assume you have already exhausted that method of search.

Zak W1VT
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K8ALM

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Re: RFI Help
« Reply #11 on: March 08, 2021, 11:50:05 AM »

I've got a Tecsun battery operated radio that I will have to put to use for this task.  I'll keep you posted as to what I find.
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K8ALM

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Re: RFI Help
« Reply #12 on: March 24, 2021, 05:29:35 AM »

I wanted to post a follow up for those who responded...the noise is gone without any action on my part.  All I could determine was the noise was outside of our house because it disappeared when I disconnected my transmit and receive antennas from the rig. I was never able to pinpoint what it was nor where it came from but it stopped. 

Thanks to those who replied.

-Tony
K8ALM
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WB8VLC

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Re: RFI Help
« Reply #13 on: March 31, 2021, 12:57:29 PM »

Like Arnold Schwarzenegger said in 'Terminator' and your noise will soon be saying,  I'll Be Back,
just wait.


If you didn't find it the first time and mitigate it then it will probably return with more of a vengeance unless you had one heck of an ice storm and most of your power grids, poles, transmission lines, wires, transformers, substations  etc. were replaced.
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N0GV

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Re: RFI Help
« Reply #14 on: May 26, 2021, 01:58:27 PM »

Looks a lot like a switching supply or fluorescent light ballast.  The periodicity of every 100 kHz is consistent with a chopper or a ballast....

Check your lights!

Grover
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