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Author Topic: Noise...started yesterday  (Read 6510 times)
N4DOV
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Posts: 52




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« on: March 28, 2013, 07:33:42 AM »

I know there are a lot of posts re this, so I apologise in advance.
Yesterday a continuous noise across all HF bands occurred wiping out reception and it continues today. On my scope it has a "pulse" type quality. Below is link to scope pictures on photobucket. Tried the "AM radio test" which did not help. Advice on what to do is appreciated.
Thanks in advance David N4DOV.
http://i1098.photobucket.com/albums/g372/N4DOV/20130328_100737_zps0cf3e6a1.jpg
http://i1098.photobucket.com/albums/g372/N4DOV/20130328_100728_zps4ae246a1.jpg
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K5LXP
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« Reply #1 on: March 28, 2013, 07:40:57 AM »

Step one - is it in your own house?

With the radio operating from a battery, shut off the main breaker and see if it's still there.  Odds are if you're receiving it across a huge swath of spectrum like that it's really close.


Mark K5LXP
Albuquerque, NM
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K2DC
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« Reply #2 on: March 28, 2013, 08:10:37 AM »

Those aren't pulses on the scope, they look more like harmonics just a few hundred Hz apart.  I agree with Mark, it's likely pretty close.  Also agree you should try operating battery and kill the house to see if that eliminates it.  If so, then go back and try one breaker at a time to see if you can narrow the source down.

73,

Don, K2DC
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N4DOV
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« Reply #3 on: March 28, 2013, 08:31:07 AM »

Really appreciate the prompt replies. Will be going to borrow battery from a nearby ham shortly. tried to connect to my neighbors(at work) electrical system... but these days they build homes without outside electrical plugs.
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W5CPT
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« Reply #4 on: March 28, 2013, 09:22:29 AM »

I would start with the obvious.  What was brought into the house just before the noise started. New phone, TV, modem, etc.  All of these could be the source of the interference.  A local ham has this happen when they installed the new washing machine.  Almost all new appliances use switching power supplies, which can be horrendous when it comes to wide spread noise.  Running off a battery is a good place to start - given that you can eliminate your own house.  I hope it IS in  because it is much harder to find in your neighbor's.

Clint - W5CPT -
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K8AXW
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« Reply #5 on: March 28, 2013, 10:08:26 AM »

Another thing to check is removing the antenna and see if the noise is still there.....if you have a beam, swing it 360° and see if the source of noise is a radiated noise like from power lines/equipment and if you can pinpoint a direction.

However, it looks like a plasma TV or something similar.  My one and only problem with radiated noise from my commercial power system had spikes a bit further apart than what you show.

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KA4POL
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« Reply #6 on: March 28, 2013, 11:33:03 AM »

Is there a time pattern to the signal? Does the signal become weaker with higher frequencies?
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N4DOV
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« Reply #7 on: March 28, 2013, 01:24:51 PM »

Thanks for further replies.
This is the outcome of my testing:

1.With battery power there is no change. Hooked the battery to my station rig with the bandscope, still as before 59 +40 noise. Then set up a portable operation ,with another radio, in my yard with battery power and a portable antenna - no change also.

2.Connected rig to neighbors electrical system, outside wall plug - no change.

3.My shack is on a different circuit from the house and is fed directly from outside, turning off circuits made no difference.

4.Turned my beam, no directional changes to noise/scope.

5.There is no new equipment/different in my house - for the last 3 years all was good, until yesterday.

6.I live in a relatively new developement. Houses are built setback to setback. The houses on each side of me are empty and for sale (I must add not because of me !!!). My back of the house is "decorated" by the utility company, no work been done there recently and never had a problem before.The highway half a mile from me is under construction, but up till now no problems and they have been at it nearly 2 years. Have not noticed any workers in my neighborhood either.

7. No change with frequency - all are equally affected.

8. Disconnecting the antenna dropped the amplitude on scope as I would expect but the spikes still showed up at the diminished amplitude.

Please help and advise me what my next step/steps should be.
Appreciate all the replies and advice,
David N4DOV.







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N4DOV
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« Reply #8 on: March 28, 2013, 01:26:27 PM »

KA4POL : there is no time pattern - continuous.
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NK7Z
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« Reply #9 on: March 28, 2013, 01:59:43 PM »

Thanks for further replies.
This is the outcome of my testing:

1.With battery power there is no change. Hooked the battery to my station rig with the bandscope, still as before 59 +40 noise. Then set up a portable operation ,with another radio, in my yard with battery power and a portable antenna - no change also.

2.Connected rig to neighbors electrical system, outside wall plug - no change.

3.My shack is on a different circuit from the house and is fed directly from outside, turning off circuits made no difference.

4.Turned my beam, no directional changes to noise/scope.

5.There is no new equipment/different in my house - for the last 3 years all was good, until yesterday.

6.I live in a relatively new developement. Houses are built setback to setback. The houses on each side of me are empty and for sale (I must add not because of me !!!). My back of the house is "decorated" by the utility company, no work been done there recently and never had a problem before.The highway half a mile from me is under construction, but up till now no problems and they have been at it nearly 2 years. Have not noticed any workers in my neighborhood either.

7. No change with frequency - all are equally affected.

8. Disconnecting the antenna dropped the amplitude on scope as I would expect but the spikes still showed up at the diminished amplitude.

Please help and advise me what my next step/steps should be.
Appreciate all the replies and advice,
David N4DOV.


I would perform the following tests:

1.  Battery power your radio.
2.  Kill the main breaker to YOUR home.  If the RFI goes away, it is you, which is good...  See notes later.
3.  Kill power to your closest neighbor...  If it goes away it is your neighbor, which is less good...  See Notes later...

That is a good start...  Do you have above ground power, or underground?  What is the highest frequency you can hear it on? 

The fact you get it without an antenna tells me it is VERY CLOSE...  It is probably your house, or a home very close to you...

Why is it good if it is your RFI, because you can stop it all on your own...  Please report back results of tests, and requested data...  Why is it not so good if it is your neighbor?  Because you are not in control of it...

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Thanks,
Dave
For reviews and setups see: http://www.nk7z.net
N4NYY
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Posts: 4749




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« Reply #10 on: March 28, 2013, 03:02:19 PM »

Can you set up a fox hunt with a local club, and try to pinpoint a source?
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WH7DX
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« Reply #11 on: March 28, 2013, 03:11:27 PM »

How about a portable radio on the lowest AM.   I did that and found that some little items like chargers were making noise at my house... that and my golf cart charger which was VERY noisy. 

Walk down the street?   Get in the car and see where it leaves and picks up again.   Might be able to narrow it down...

$.02

Bryan
WH7DX
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N4DOV
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Posts: 52




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« Reply #12 on: March 28, 2013, 03:46:48 PM »

NK7Z, Dave: have done the tests.  Went to all 3 of my surrounding neighbors (behind my home is a concrete fence and a road) and switched their power off as well as mine and on battery power made no difference. The noise is on all frequencies from 1.8 to 50 MHz. Power is underground in my neighborhood. Raised electrical wires pass behind my house travelling to/from a substation 1 mile away. Never had any problems till yesterday.None of my immediate neighbors have electrical fences or invisible dog fences.

WH7DX Bryan: did the AM radio walk thing last night made no difference where I was.

N4NYY: Will have to work on getting local club involved.

Interestingly the noise did drop for about 30 or so minutes to half its level. But most of the time it is 59+40.
So my sad tale continues.

Any other advice is much appreciated.
Thanks David N4DOV.
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NO2A
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« Reply #13 on: March 28, 2013, 04:01:29 PM »

With a 5/9plus 40db noise source it has to be very close. I`d try driving around your neighborhood with your car on an empty am frequency. Is it a buzzing noise,like power line noise would be?
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N4NYY
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« Reply #14 on: March 28, 2013, 04:10:34 PM »

Dave,

Someone on this board was mentioning a new style of gas street light that is noisy for like a half mile. Check into any light if you can get a fix hunter involved. I also believe with the signal strengths, that it is very close.
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