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Author Topic: grrr noise...  (Read 837 times)
W6NZX
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Posts: 451




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« on: March 06, 2008, 07:08:35 AM »

I basically have a noise problem that wont go away, that the UTIL companies refuse to fix and that I lack the skill to REALLY track down.

So I wonder would one of these help?
http://www.mfjenterprises.com/Product.php?productid=MFJ-784B

So far as cutting out different flavours of interference?

-R
W6NZX
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WA3SKN
Member

Posts: 5480




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« Reply #1 on: March 06, 2008, 07:30:21 AM »

I can say that this IS NOT the solution to your noise problem!
You need to determine how the noise is getting into your radio... via antenna, power line, or by direct radiation.
1. Disconnect the antenna, do you still have the noise? (probably not!)
Next, try operating off a battery (power line noise).
Then, use a Faraday shield (aluminum foil wrapped around rig) to block direct radiation.
I'll bet the noise leaves when you disconnect the antenna!
If the noise is incoming via antenna, its time to isolate it.  Try running your radio off a battery while throwing house breakers, hopefully the noise will be generated in your house. Then check eqpt being fed by the breaker.
If not in the house, a long piece of coax and a small sensor loop/coil can be used to try and locate.  A portable radio can help track the noise here!
Good Luck!
73s.

-Mike.
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K1BXI
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Posts: 812




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« Reply #2 on: March 06, 2008, 10:25:46 AM »

The 784B probably is not what you want as was stated. However I have had success phasing out local noises with the MFJ-1025 <http://www.mfjenterprises.com/Product.php?productid=MFJ-1025>
If you have an understanding of phasing signals, this unit will do a very good job on any one noise at a time as long as the sensing antenna hears the exact same noise wave form as your station antenna. I have dropped an S9 plus noise down to S1 or less without any drop in the station I want to copy. This may take a little work to get both antennas to hear the exact same signal, but when you do, a few careful adjustments will phase the noise signal to a very low value.

Many hams buy one of these and hook it up and find that it won't do the job they expect out of the box and give it the old "mighty fine junk" tag and sell it at the nearest ham fest. You may have to try different sensing antennas for a particular noise. With the right one it will do the job.  

Of course the best solution by far is to eliminate the noise at the source.

John.....K1BXI
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W5DXP
Member

Posts: 3582


WWW

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« Reply #3 on: March 06, 2008, 10:34:38 AM »

Going from a vertical monopole to a horizontal dipole improved the noise situation at my previous QTH by 2 S-units.
--
73, Cecil, w5dxp.com
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73, Cecil, www.w5dxp.com
The purpose of an antenna tuner is to increase the current through the radiation resistance at the antenna to the maximum available magnitude resulting in a radiated power of I2(RRAD) from the antenna.
N1QOQ
Member

Posts: 188




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« Reply #4 on: March 06, 2008, 01:57:27 PM »

Are you sure it's powerline noise? Battery chargers and other things like door bell transformers can make noise like that.  73 Paul
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K1BXI
Member

Posts: 812




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« Reply #5 on: March 06, 2008, 04:28:32 PM »

I think I should add this:

You didn't say what your antenna was and what frequency's you were hearing the noise on. A dipole will have less noise pickup than a random length of wire in most cases. Some have less local noise pickup with a closed loop antenna or a folded dipole. If it is power line noise many times it will diminish on a rainy day.   Maybe you could change the position of the antenna relative to the power lines etc. Do what the posters above have suggested. If you find the source of the noise and can fix, or have it fixed, all the better. And at a very low cost to you.

Do all these things before investing in any more equipment. You may luck out, but the airwaves are getting full of more noise generators everyday. Find one noise source and no sooner silence it and another one pops up.

Best of luck.

John.....K1BXI
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W3ML
Member

Posts: 166




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« Reply #6 on: March 06, 2008, 06:46:56 PM »

If you prove it is not coming from you, then call the company back and instill that they check the area.

My Electric company is coming to our town a second time after fixing a lot of problems last summer.

If you don't get satisfaction from the Utility Company, then file a complaint with the FCC.

They have contacted these companies before and explained the law to them.  They have to fix the problem if it is their problem.

John
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W6NZX
Member

Posts: 451




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« Reply #7 on: March 06, 2008, 08:16:19 PM »

let me just add i have been over ALL  the basic trouble shooting I know.

radio to dummy load = no noise.
throwing all the breakers in the = still get noise.
disconnected grounds FROM the radio and tuner still get noise.
Driven around / walked around an 8 block radius with an AM radio tuned to an empty freq --can't find any noise.

I am at a loss.
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W6NZX
Member

Posts: 451




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« Reply #8 on: March 06, 2008, 08:28:15 PM »

Three things:

1. 17M is dead quiet and I have worked alot of contacts on it.

2. Just tried wrapping the rig in tin-foil --nada change.

3. This interference is getting worse and worse.

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W6NZX
Member

Posts: 451




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« Reply #9 on: March 06, 2008, 08:34:58 PM »

G5RV sloper from about 30ft down, but i had no noise in this config, then one day like someone through a light switch *noise*.
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KK7KZ
Member

Posts: 464




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« Reply #10 on: March 07, 2008, 05:19:41 AM »

Have you considered going to Radio Shack and picking up a cigarette lighter plug and hooking it to  your radio, putting your rig in the car with some kind of wire antenna, plugging it into your car's lighter socket and, after tuning up the noise problem, drive around to see what results you get?
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WA3SKN
Member

Posts: 5480




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« Reply #11 on: March 07, 2008, 05:53:55 AM »

OK, the noise is incoming on the antenna jack (this is good).
Since an AM radio does not hear it, you will need a receiver that does.  Preferably portable, and with some form of directional antenna.
What frequency band(s) do you hear the noise on?
Is there a "time-of-day" issue here?
Can you make a simple "shielded Loop" antenna for that frequency (for DFing the noise)?

-Mike.
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AD5VM
Member

Posts: 26




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« Reply #12 on: March 07, 2008, 05:20:39 PM »

I had a 'grr' noise also, it turned out to be a touch lamp in the next room. It made the noise even if it was turned off!
At my previous QTH I had a problem with power line noise and the MFJ-1026 would bring it from an S9 to about an S1 but like a previous post said, it didnt happen right out of the box. The sense antenna has to hear the same exact noise so if you have a 5 element quad pointed right at the power substation across the street, then you'll probably need a second 5 element quad as the 'sense' antenna hihi. I was able to use a small six meter dipole that I put up near my main antenna (pointed in the same direction) and that worked just fine but it's not magic. Just phase inversion.
If you have a big pile of money, you could get the DX engineering version which may be better:

http://www.dxengineering.com/Products.asp?ID={6F07CEB4-27D0-4664-A2AA-352A69ED88CD}&SecID=114&DeptID=12
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AD5VM
Member

Posts: 26




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« Reply #13 on: March 07, 2008, 05:27:00 PM »

I once read an article about a guy who had the same problem. Turned out to be a doorbell power supply in a house like two blocks away! He tracked it down with a portable SW radio.

You could build a small loop antenna with some magnet wire and a pizza box.
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K1BXI
Member

Posts: 812




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« Reply #14 on: March 07, 2008, 07:19:43 PM »

Try listening to the various mp3 recordings of different rfi sounds here. You may be able to narrow down the device that is causing the noise if you can match your noise with one of these sounds.

http://www.arrl.org/tis/info/HTML/rfi-noise/

John.....K1BXI
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