HFU HF Underground
Technical Topics => Equipment => Topic started by: rdla4 on May 01, 2012, 2341 UTC
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About a week ago, someone close by started using something that operates 24/7 that generates a 10 over S9 signal pretty much from DC to light (Including 6925......!) I have moved my un-un fed longwire to no avail. Tonight I decided to try a home brew phasing system, using an indoor loop lightly coupled to the longwire. The loop is resonated to produce a null based on the loop position. While I do not get nearly the signal that I had previously due to the light coupling, I am happy tonight to hear distant static crashes and a few pesques on the band rather than this constant high level buzzzzz. I can hear the carrier from Israel on 6973 tonight. The only PIA to this whole mess is having to retune the loop every few 100 khz to keep the noise at bay. It makes casual hunting of signals problematic, but at least I should be able to have some signals show up from time to time.
I notice that MFJ makes a phasing product for "cancelling noise". Anyone had experience with it? The MFJ 1026 is the model I think.
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I have a MFJ 1026 here. I don't use it for noise canceling, but have used it for nulling out local MW stations, which is pretty much the same principle.
You need two antennas that have different radiation patterns. What you do is adjust the amplitude and phase controls on the 1026 so that the signal from the two antennas is of the same amplitude but opposite phase for the offending signal. When these two signals are mixed, they cancel out, nulling out that offending signal. The phase and/or amplitude of the station you want to hear must not be the same, so that it is not also nulled out.
You do need to re-adjust the 1026 as you change frequencies, so it may or may not be better/easier to use than what you have now.
Have you tried DFing the interference with a portable? If it is a faulty piece of electrical distribution equipment, you should be able to get the utility to repair it.
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Thanks for that info on the 1026. I do have two outside antennas, both are in the field of whatever this is.As far as DFing----yes, tried that. It is very widespread thru the neighborhood. I have it down to three houses. My neighbor, directly next door, or his neighbor or a house on the next block over.
Sad----this has always been a nice quiet RF area. Closest broadcast is 15 miles away, its 50kW, But I am in the null. Underground utilities I was normally limited by atmospherics and a very few birdies from my PC, which has ferrite hanging all over it.
This seems to work OK, but my home made solution works from about 5mhz up to around 15 mhz, I may have to build a different loop or just buy the 1026 to add some bands.
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Sharing a recent experience of a friend of mine-
Had wide band (hf-uhf) noise with a peak around the 300Mhz region.
>:(
Discovered it was caused by a faulty plasma television.
The noise was immense- worse I've ever heard on such a wide
frequency spectrum.
Hope you find relief!
Cheers!
weaksigs
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Thanks for the messages...
I did buy a MFJ 1026, and got it installed lastnight. I was able to hear RML weak last night, averaging S3 here, by placing a deep-deep null on the mystery noise. The noise I have is S9 on a meter, but it contaminated any kind of AM signal here.
I am still learning this thing---it takes a bit of patience to get a null everywhere.
But it is nice to hear a few signals today on various bands.
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Glad to hear the 1026 is helping!
FYI - IIRC there is a mod (details online, although I don't recall the URL) for extending the range down to lower frequencies. I believe it involved removing some inductors?
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There is a mention in the book of a BCB filter that you can remove if there is no BCB QRM.
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That sounds like it!
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My 2cents. I have S7-9 noise coming from the electric supply coming into the house. It isn't any single circuit within the house. When any circuit in the house is on, the noise is there. So I got a Timewave ANC4 taking the risk of returning with a 15% restocking fee. I tried everything from a 6 inch stub to a full 40 meter dipole the opposite direction of the primary. About 7-8 different lengths and orientations. Net result was really right next to zero. The noise is so close and pervasive that it did no good so it got returned. It is good to hear you are able to get a little relief.
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Sorry that did not work for you. I have found a few places on HF where I cannot get a "reasonable null" from the MFJ in my noise. (For instance 11Mhz, thru about 13.5mHz. I can null the noise in this range, but I attenuate so much signal as well, that it is pointless. Everywhere else it seems to work fine. My noise is from one direction---lucky.
In your case, where the noise is riding on the mains, thats tough to get rid of, since is is more likely the the noise is surrounding you.
When it cools off, I am going to change my antenna around a bit---namely higher elevation which I think will help quite a bit.
(For a Yankee in GA, that will be about November for cooling off)