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Author Topic: Rfi below the 80 band every 20 to 30khz  (Read 1876 times)
KC6RWI
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Posts: 210




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« on: June 24, 2019, 12:13:01 PM »

I'm using an ic7300. I was tuning the 80 meter band and going down to 160 just turning the dial and listening. I found that every 20 to 30 khz I had a straight line signal making noise. To describe the signal its like an arrow head above the first grid line and a straight line below. Today I have the radio in another location, miles away and I don't have that sort of interference. I disconnected a number of items in the house, the modem, tv, refrigerator, a few wall warts, but no change.
On my list of things to buy is a gel cell to further the search.
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KC1GCG
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Posts: 191




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« Reply #1 on: June 24, 2019, 08:38:31 PM »

Try any of those outdoor solar charging LED lights outside. My wife loves them but seems like 3 out of 4 of them throw off rfi. Good luck! John k1 jrf
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KC6RWI
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Posts: 210




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« Reply #2 on: June 25, 2019, 07:49:47 AM »

I am thinking along those lines, it was a very hot day so solar arrays be doing their max output. I'm hoping someone who has had that type of rfi will confirm that it the type I have.
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WB4SPT
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Posts: 782




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« Reply #3 on: June 26, 2019, 08:13:38 AM »

...
On my list of things to buy is a gel cell to further the search.

Almost certainly, a small transistor AM radio will work.   Mine is a 1964 Zenith pocket sized with a pretty directive ferrite antenna inside.   Wink
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KC6RWI
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Posts: 210




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« Reply #4 on: June 26, 2019, 01:19:18 PM »

I'm doing a mental inventory, I don't think I have an am radio. When I do find one, I should probably tune to one end of the band with no station. I've never tried this, there is a solar panel array a few houses away.
« Last Edit: June 26, 2019, 01:32:32 PM by KC6RWI » Logged
NK7Z
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« Reply #5 on: June 27, 2019, 10:55:43 AM »

See:

https://www.nk7z.net/i-have-rfi-now-what-locating-it/

for a step by step on how to locate RFI...
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Thanks,
Dave
Amateur Radio: RFI help, Reviews, Setup information, and more...
https://www.nk7z.net
KC6RWI
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Posts: 210




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« Reply #6 on: June 27, 2019, 04:36:14 PM »

thanks, I read the link, now I am itching to get to work and find the source. I think finding source is good thing, as it maybe something breaking down, like a door bell transformer. My rfi signal seems like an arc to me. A few months back my mobile radio was picking up some ignition noise, I didn't realize that it was an indication of a spark wire breaking down. Later one morning I had a no start and the electrons in the main distributor wire found their own path of less resistance.
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NK7Z
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« Reply #7 on: June 27, 2019, 05:29:34 PM »

Glad it helped!!
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Thanks,
Dave
Amateur Radio: RFI help, Reviews, Setup information, and more...
https://www.nk7z.net
KC6RWI
Member

Posts: 210




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« Reply #8 on: July 02, 2019, 09:57:47 AM »

I found that the signals I hear are slowly drifting down, I had the radio on lower sideband and I had less than 2 minutes before the signal would sweep down.
How can I be sure I am not dealing with a signal that is transmitted with intelligent design, and not one that is created by a malfunction, such as an arc?
I've have a NRD 525 shortwave receiver and I did a comparison to these signals I hear on the ic7300. The NRD525 did hear the signals but in comparison the signal was 1/5 of what the 7300 heard. I wonder if what I am hearing is something do with the sdr radio characteristics.
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NK7Z
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« Reply #9 on: July 02, 2019, 12:27:45 PM »

I found that the signals I hear are slowly drifting down, I had the radio on lower sideband and I had less than 2 minutes before the signal would sweep down.
How can I be sure I am not dealing with a signal that is transmitted with intelligent design, and not one that is created by a malfunction, such as an arc?
I've have a NRD 525 shortwave receiver and I did a comparison to these signals I hear on the ic7300. The NRD525 did hear the signals but in comparison the signal was 1/5 of what the 7300 heard. I wonder if what I am hearing is something do with the sdr radio characteristics.
Not sure what you are asking, but I think you are asking what is causing the RFI...  Unable to tell...  Not enough information. 

What were the results of the home power off test described on my web page?  Is the source in your home, or external to your home?  Here is a link to a series of articles covering how to locate and remove RFI from your local environment:

https://www.nk7z.net/category/info/rfi-mitigation/i-have-rfi-series/

You will need to read them and understand the articles there, they may assist you in solving the issue you are having...
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Thanks,
Dave
Amateur Radio: RFI help, Reviews, Setup information, and more...
https://www.nk7z.net
K0UA
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Posts: 4789




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« Reply #10 on: July 03, 2019, 09:34:43 AM »

Let me know what you find. I have them here too. They are not in my home, that much I know. yes they drift and are unstable.
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73  James K0UA
ARRL Missouri Technical Specialist
KC6RWI
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Posts: 210




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« Reply #11 on: July 04, 2019, 01:48:04 PM »

Yes NK7Z, I did run thru the flow chart and Have done a lot of reading, I did run the radio off of battery and I still had the inference. Mt real question is, how do can you tell the difference between a transmitted final and an rfi signal. I hear a signal that is the same strength and its 20 to 35 kHz apart over much of the band from 80m to 160m. I live 7 miles from JPL, so I don't know if i am hear some sort of radar, or another kind of rfi. I did carefully go thru the page you have on examples of rfi and I didn;t see any that matched. Thanks again for time.
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NK7Z
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« Reply #12 on: July 04, 2019, 05:12:58 PM »

Yes NK7Z, I did run thru the flow chart and Have done a lot of reading, I did run the radio off of battery and I still had the inference. Mt real question is, how do can you tell the difference between a transmitted final and an rfi signal. I hear a signal that is the same strength and its 20 to 35 kHz apart over much of the band from 80m to 160m. I live 7 miles from JPL, so I don't know if i am hear some sort of radar, or another kind of rfi. I did carefully go thru the page you have on examples of rfi and I didn;t see any that matched. Thanks again for time.
More then likely the source is close to you, as opposed to distant.  By close I mean within a mile or less.  More likely within 1000 feet of you.  If you are seeing a lot of related signals using the method outlined in SDR as a site survey tool, located at:

https://www.nk7z.net/sdr-rfi-survey-p1/

then you are probably seeing SMPS, (Switching Mode supplies), as the cause.  Most RFI is local in nature, and most RFI is caused by SMPS scattered around your, and your neighbor's homes.  If it were me, my next step would be to get an SDR and a loop and start looking around the area.

You won't see matched signals in the snapshot pages located at:

https://www.nk7z.net/rfi-snapshots/

to your RFI, you will see generalities in behavior there, which can help to ID a source, but until you locate the source, you are only guessing.  RFI location is both an art, and a science...  The art part is your learning to listen to RFI, and be able to pick one source out from a number of sources,  the science part is being able to build loop antennas, and know how to use them.  That sort of thing...  Respectfully, you are undertaking a project that requires a lot of background knowledge, some of which you may not have yet, If you have a local club in your area, get hold of someone there that can assist more directly in RFI locating, and learn from them, then you will be able to locate a source in short order, and help others...  Having someone to mentor you is important, and it is good hamming!  Hope this helps, and please feel free to write me directly anytime you have a question, I will do what I can from several hundred miles away... 
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Thanks,
Dave
Amateur Radio: RFI help, Reviews, Setup information, and more...
https://www.nk7z.net
KL7CW
Member

Posts: 604




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« Reply #13 on: July 11, 2019, 03:24:42 PM »

It is not at all unusual  to have several sources of RFI.  Often lower frequency RFI is propagated longer distances over power lines, etc.  So sometimes it is easier to localize the RFI by going to the highest frequency you can hear it and try and narrow it down.  For example if you can still hear the RFI at 5 or 6 MHz or whatever try this frequency.  I have had some success just driving my car around the area with the AM radio tuned to the RFI on an unused frequency.  One time I located an electric fence over a mile away with this method.  Frequently the RFI is from your own house, so the only sure way to eliminate it is to turn off the main breaker.  If there are several sources, turning off one breaker at a time may not help you locate it. 
         Good Luck   Rick   KL7CW                     
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ZENKI
Member

Posts: 1648




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« Reply #14 on: July 13, 2019, 06:49:35 PM »

I have been go to guy at the ham club for "finding" all the crap and crud. Recently I have added a  high Dynamic Range Active Antenna in form of  MiniWhip. The readily available kits typically have a PCB antenna. What I did was  solder on a 1 meter telscopic whip that goes as long as 1.2 meters. I  use a professional EMC receiver with a 9khz quasi peak bandwidth. I can calibrate these antennas  using  the capacitor substitution method so I can actually try and determine the radiated emission limit. Although verticals are not the approved type of antenna for CISPR EMC regulations measurements. Typically the authorities us 60cm  loops which have  very high pre-amp noise and cant really measure  the real noise levels that cause problems to hams. I have access to all these useless 10,000 dollar loops at work  and simple ham tuned loops outperform them right down and below ITU rural quiet noise levels.

But getting back to the point the MiniWhip with a low pass filter connected to the  typical Chinese shortwave radios make an excellent RFI finder.  With the telescopic whip down  which is typical low sensitivity you can just hold this antenna out of the window and do a drive by survey of the street. With the Whip down you can adjust to a horizontal position and reduce the omni-directional characteristics of active verticals and also use the stray capacitance of the car body that reduces received signals to virtually pinpoint the house or noise source general location

Unfortunately most of the cheap shortwave radios and hand held radios dont have enough dynamic range and filtering to handle an active antenna. I have been using a K3, K2 and even a Drake R7A that can handle  professional EMC Mil Standard Active Antennas such as loops and verticals. A 30db or even a 40 db attenuator along with a low pass filter helps tremendously.

One thing That I have found recently is that a  lot of Chinese switch mode chargers seems to have a noise peak in spectrum from roughly 4mhz to 10mhz, with the peak somewhere between 5 and 7 mhz. This makes it  easy to find the noise at high noon, assuming its not those horrible solar garden night lights.

Electric bikes, scooters and wheel chair type scooter chargers seem to be popping up everywhere and   the 48 volt chargers  can throw out radiated emissions that can be worst than plasma TV noise. I just recently tracked down a  48 volt E bike charger that was throwing  S9  hash across  a 100 acre field it was so filthy. Our Authorities dont care about the rubbish that is flooding the market, they are really good at telling hams not interfere and ignore all the CISPR regulations that they claim is law. Its EMC policy framework is a universal failure and self compliance is just one big fraudulent industry  that is dominated by cheats.

Unfortunately noise finding is becoming a daily chore  as more and more self certified rubbish from places like China flood the market while our authorities ignore and dont enforce the regulations. I would almost go as far as saying they using  this flood of crap equipment  as backdoor way of killing off HF ham  radio as we know. Why I say this is because the EMC mitigation techniques now exist that  cant certify all industrial and domestic  equipment to be better than Class B FCC and CISPR standards. Its just that our regulatory agencies have given companies a license to pollute the spectrum without justification.

I'm using an ic7300. I was tuning the 80 meter band and going down to 160 just turning the dial and listening. I found that every 20 to 30 khz I had a straight line signal making noise. To describe the signal its like an arrow head above the first grid line and a straight line below. Today I have the radio in another location, miles away and I don't have that sort of interference. I disconnected a number of items in the house, the modem, tv, refrigerator, a few wall warts, but no change.
On my list of things to buy is a gel cell to further the search.
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