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Message from vitesse at Sunday, 05-Sep-10 23:10:24 GMT
Can someone could have a clue of what can bring this kind of QRM:
Mostly on 80m band, the sound can be heard every 20km like 3.740, 3.760, 3.780, but the frequency is not stable. It's sad as this is arond 3.750 at 4pm (when a quebec ham network operate and at 7pm at 3.780 when another quebec ham network operate.) Here a sample of what the audio is in mp3. I tunned at 3.78 - 3.79 - 3.80 - 3.81 - 3.8 - 3.81 then 3.8 (in USB)
Radio Used: Icom 706mkIIg antenna is a center feed zepp. thanks for your help. Location is the same as my GT node :)
audio:
http://fmdx.gotdns.com/download/QRM.mp3
Mostly on 80m band, the sound can be heard every 20km like 3.740, 3.760, 3.780, but the frequency is not stable. It's sad as this is arond 3.750 at 4pm (when a quebec ham network operate and at 7pm at 3.780 when another quebec ham network operate.) Here a sample of what the audio is in mp3. I tunned at 3.78 - 3.79 - 3.80 - 3.81 - 3.8 - 3.81 then 3.8 (in USB)
Radio Used: Icom 706mkIIg antenna is a center feed zepp. thanks for your help. Location is the same as my GT node :)
audio:
http://fmdx.gotdns.com/download/QRM.mp3
Message from Ginny at Tuesday, 07-Sep-10 11:30:27 GMT
Vitesse,
This may be the harmonics of a switching power supply. They are notoriously noisy, and ubiquitous. To track one down, start by unplugging wall power supplies one at a time throughout your house, to see if it stops. After you unplug one, give it several seconds to die down. Check not only the ones in the radio room, but in adjacent rooms as well. If you find it, post another message and we can talk about how to cure the interference.
Scott
NM8R
Michigan
This may be the harmonics of a switching power supply. They are notoriously noisy, and ubiquitous. To track one down, start by unplugging wall power supplies one at a time throughout your house, to see if it stops. After you unplug one, give it several seconds to die down. Check not only the ones in the radio room, but in adjacent rooms as well. If you find it, post another message and we can talk about how to cure the interference.
Scott
NM8R
Michigan
Message from vitesse at Tuesday, 07-Sep-10 12:50:06 GMT
Many thanks, will try this today :)
Message from W1WCN at Thursday, 09-Sep-10 23:24:04 GMT
Vitesse, I agree with Scott. It sounds like a switching power supply. Do you have any computers nearby (or maybe not even nearby)? Notebook computer power supplies are particularly troublesome, especially if they are aftermarket replacements.
It really helps to have someone to go and unplug power supplies while you listen. It's very difficult to trust your ears when you walk back into the shack to listen or sometimes the noise will stop on it's own while your walking back to listen and you'll mistakenly think the power supply was the culprit. When I'm by myself I stream the audio to the internet using livestream.com or stickam.com and listen on my smartphone. That way I get instant feedback. This save a lot of time,too.
I hope you find the problem. It's frustrating.
And why does it seem that RFI always seems to find the specific frequency you want to listen to at the specific time that you want to listen. Conspiracies...conspiracies I tell ya'.
It really helps to have someone to go and unplug power supplies while you listen. It's very difficult to trust your ears when you walk back into the shack to listen or sometimes the noise will stop on it's own while your walking back to listen and you'll mistakenly think the power supply was the culprit. When I'm by myself I stream the audio to the internet using livestream.com or stickam.com and listen on my smartphone. That way I get instant feedback. This save a lot of time,too.
I hope you find the problem. It's frustrating.
And why does it seem that RFI always seems to find the specific frequency you want to listen to at the specific time that you want to listen. Conspiracies...conspiracies I tell ya'.
Message from vitesse at Friday, 10-Sep-10 01:14:49 GMT
Ok so I unplug things inside the house... I finally removed everything from the wall and Finished with closing all breaker except the one driving the radio.
So only the radio and is power supply was working. (A Switching power supply).
So maybe this is coming from a neighbour. Will try to investigate more this week end if I found time. One thing I see is that the signal drift (slowly) in frequency and is not always at the same spots
As for tracking I can always listen to my Saint-jean HF node with my portable.
So only the radio and is power supply was working. (A Switching power supply).
So maybe this is coming from a neighbour. Will try to investigate more this week end if I found time. One thing I see is that the signal drift (slowly) in frequency and is not always at the same spots
As for tracking I can always listen to my Saint-jean HF node with my portable.
Message from Ginny at Friday, 10-Sep-10 11:34:12 GMT
Vitesse,
The spurs from switching power supplies often drift, as you describe.
Another thing to consider in your search would be wired ethernet spurs, that is, radiation from cat 5 cables.
The possibility of it originating at a neighbor's home complicates the matter. If you do find the source and can attempt to suppress it, there is an excellent tutorial available on RFI suppression by a gentleman named Jim Brown, I can direct you to.
W1WCN makes an excellent point about seeking the help of another person to listen in the radio room for subtle changes in level, especially if you start adding ferrite chokes to suppress the noise.
Best of luck. Don't give up.
Scott
NM8R
The spurs from switching power supplies often drift, as you describe.
Another thing to consider in your search would be wired ethernet spurs, that is, radiation from cat 5 cables.
The possibility of it originating at a neighbor's home complicates the matter. If you do find the source and can attempt to suppress it, there is an excellent tutorial available on RFI suppression by a gentleman named Jim Brown, I can direct you to.
W1WCN makes an excellent point about seeking the help of another person to listen in the radio room for subtle changes in level, especially if you start adding ferrite chokes to suppress the noise.
Best of luck. Don't give up.
Scott
NM8R
Message from hotshot at Wednesday, 29-Sep-10 11:13:58 GMT
any update on this topic?
Message from vitesse at Wednesday, 29-Sep-10 22:17:46 GMT
No new updates as I had no time to play with that. I planned to use a small portable radio, but the interference is not really audible in AM mode. I should try to search again soon on my neighbour house.
Message from vitesse at Monday, 11-Oct-10 23:13:39 GMT
I think I have found the source of my problem. It was the Power supply I was using to operate the radio.
I had different kind of bug that I was supecting it was du to poor antenna instalation and it apear it was due to the PSU and since I use a 12v battery I don't have this trouble.
I had different kind of bug that I was supecting it was du to poor antenna instalation and it apear it was due to the PSU and since I use a 12v battery I don't have this trouble.
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