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Author Topic: Intermittent RFI issue from 10 - 20 meters - Need advice  (Read 9138 times)
KD2CJJ
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Posts: 369




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« on: April 25, 2014, 11:38:53 AM »

I see what looks like to me to be a 60hz??... it looks like on my radios scope a sine wave cycle up and down (or spikes ever so many Hz) with bands being affected between 10 meters to 20 meters with 15/17 meters being the worst.  It sounds like a Hum with a little buzz to it... its constant no crackling....  I can go days or even weeks without seeing it but all of a sudden its back on all the time.  I have not been able to pin point whether weather improves or degrades the situation as other noises come into play when its rainy or windy

This problem is SEVER.  When its apparent its a S9+ on 15 or 17 meters but some times its much smaller and not even bother-sum.    Whats odd is that the issue does NOT occur below 20m. 40m ---> 160m you dont eve hear the noise..

I believe its 1 of three things... The transformer in my back yard --  I have a beam antenna so I know the direction... When its directly pointed at the transformer, the noise peaks but I believe its a Low probability since it can go away from one day to the next.  If its the transformer, wouldnt it be all the time no matter day, night, etc. ;

The street lights medium probability but I don't believe it because some times it goes away completely.  Street lights come on at night -- but every night...

Lastly a neighbor -- Most likely situation.   I know its not my house as I have done the turn everything off in the house and its still there (though my noise level drops by 2S points!).  It could be a neighbor BUT I have yet to find the pattern without being in their house.

The questions I have:
1.  What equipment do you suggest I use to narrow down the source?  I am willing to spend a little money to supplement my gear.  I have only large HF rigs OR 2m/70cm hand held.  My little AM radio DOES NOT pick up the source when its occurring.. in fact if I turn my beam away from the sources it goes to virtually no noise... so I know I need something directional and small enough to walk around.
2.  How do you suggest I approach the home owner if it is a home owner?

Mike, KD2CJJ
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Mike
KD2CJJ
KI6LZ
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Posts: 586




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« Reply #1 on: April 25, 2014, 12:05:33 PM »

Had similar problem here. Took lots of coordination with electric company to have their RFI/EMI tech out here when the noise was present. Did a lot of recording with Smeter lite to try to come up with the most likely times for the noise to occur. In my case the noise stopped between 9am and noon, and started back up around 2 hours after sunset. Not always but say 70% of the time. The noise also sometimes came on and stayed for 24 hours for several days. And some days no noise at all.

Turned out to be the lightning arrestors that were pinpointed using an ultrasonic dish receiver. These are some new fangled type arrestors with are replacing the older less noisy types because the older ones can fail in a way that can cause a fire hazard to brush surrounding the pole. Took 4 months to replace once they were identified.

May not be the same problem you have but identifying the noise required at least an ultrasonic detector.

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KD2CJJ
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« Reply #2 on: April 25, 2014, 12:50:33 PM »

Well... whats funny is this last event lasted 2 days with a fury.. it was the loudest I have heard it in a while.....  it happend right after a major wind storm.  Now its completely gone as of this morning... it may or may not come back though...its really frustrating.

I looked up ultrasonic detectors and they are crazy expensive from what I can see... out of my price range for this issue...

but you have given me some good advice though and some hope.

Had similar problem here. Took lots of coordination with electric company to have their RFI/EMI tech out here when the noise was present. Did a lot of recording with Smeter lite to try to come up with the most likely times for the noise to occur. In my case the noise stopped between 9am and noon, and started back up around 2 hours after sunset. Not always but say 70% of the time. The noise also sometimes came on and stayed for 24 hours for several days. And some days no noise at all.

Turned out to be the lightning arrestors that were pinpointed using an ultrasonic dish receiver. These are some new fangled type arrestors with are replacing the older less noisy types because the older ones can fail in a way that can cause a fire hazard to brush surrounding the pole. Took 4 months to replace once they were identified.

May not be the same problem you have but identifying the noise required at least an ultrasonic detector.


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Mike
KD2CJJ
K9RJ
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Posts: 33




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« Reply #3 on: April 25, 2014, 10:51:49 PM »

I think the idea may be to get the power company to come out with their ultrasonic dish.
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KI6LZ
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Posts: 586




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« Reply #4 on: April 26, 2014, 12:00:28 AM »

Some more info. I did drive around with a CB mag mount antenna listening to 17 meters and found the noise mostly confined to the power line run some 300 feet from the house. I really couldn't narrow it down any further because the noise dropped rapidly off at 50 MHz with nothing on 2 meters. Used a Grundig portable receiver.

I got lucky that the noise was present during his second visit, he had to leave his house at 5am to get here at before 8am.

Bottom line is that the power company rep has to identify the noise problem and write up a problem/work request. I almost bought a detector from midnightscience but glad now that I did not spend the money.

Frustrating that the noise was at best 40% predictable.
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KD2CJJ
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Posts: 369




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« Reply #5 on: April 26, 2014, 05:23:11 AM »

The kicker is for me the noise is almost completely gone now..it was a s9 now a 0... I can still hear it with am on 17 meters and with preamp with the beam towards the culprit...what's the culprit I don't know...

What do you think about these?
http://www.dxengineering.com/search/part-type/power-line-noise-finders/product-line/mfj-power-line-noise-finders?autoview=SKU&sortby=Default&sortorder=Default
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Mike
KD2CJJ
KI6LZ
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Posts: 586




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« Reply #6 on: April 26, 2014, 10:56:09 AM »

As mentioned above, the noise could not be heard on 2 meters. I tried using a HT with a 3 el portable 2 meter antenna.
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K8KAS
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« Reply #7 on: April 29, 2014, 07:40:45 AM »

 Grin
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K8KAS
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Posts: 569




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« Reply #8 on: April 29, 2014, 07:44:08 AM »

I have the same problem on 40 meters, the slow power co and I working on the problem, as yet nothing done to clr the noise..
You have to look for the noise with a AM demod on the rcvr, a FM hand held will not hear it...Denny K8KAS
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KI6LZ
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Posts: 586




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« Reply #9 on: April 29, 2014, 10:25:51 AM »

Used AM demod on both 50 MHz and 144 MHz, no noise detected. On 144 used 3 el beam. Seems the noise these arrestors make is between 18 and 30 MHz for some reason.
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N3HEE
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Posts: 117




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« Reply #10 on: April 29, 2014, 10:55:39 AM »

If you think it's power line noise then you need to first open a trouble ticket with the power company.  They will assign a technician.  The tech will come to your QTH with the equipment required to get a noise signature while connected to your antenna.  Every noise has a unique signature.  The tech will then drive around and locate the noise source that matches your noise signature.  The tech will then document his findings and schedule a line crew to fix any hardware that was identified as causing your noise.  This can be a very long and drawn out process depending if there are multiple noise sources, bad weather and heavy line crew work loads.  Please be patient, kind and courteous with the tech.  

Do yourself and the tech a big favor by NOT trying to find the noise source on your own with a VHF/UHF radio and yagi.  You will find noise sources everywhere!  It is highly unlikely you will find the "correct" noise source.  You don't want to create a wild goose chase.  I have learned this lesson working with my technician on solving my noise problems.  

I am currently on round two of solving my power line noise problems.   On round one the tech identified and fixed a broken lightning arrestor.  This only solved part of the problem.  He came back a second time and has identified three more noise sources matching my "new" noise signature.  It has been about 6 months to get to this point.  Hopefully after they fix the second round of problems I will be noise free.  

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KI6LZ
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Posts: 586




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« Reply #11 on: April 29, 2014, 11:12:16 AM »

Agree with above. There are a lot of noise sources around that may not be the ones causing your problem. One way I found to work is to place your phone near the radio speaker and then driving around listening to both the noise detector output and cell phone to correlate the two. This works if there are pauses in the noise or some other characteristics that can match both. Otherwise you'll find an overwhelming amount of noise sources which may not be the source of your problem.

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KD2CJJ
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Posts: 369




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« Reply #12 on: April 30, 2014, 03:51:38 AM »

KI6LZ  --- yes this seems to be my observation at my station...  BUT I can also pick this up at or around the 1700khz on my AM radio --- the question is, is it the SAME noise source I am hearing at from 28Mhz down to 18 Mhz --- which are the bands I care about...

You guys have some good points and I see why its probably a good first step to contact the power company than try to find the source myself.  The challenge I also face is that the power lines run behind homes thus I can not just jump into someone yard -- Here in NY you liable to get a beat down --- no such thing as a friendly neighbor LOL!

I did drive around with the am radio on at the highest point of the bc band.. And I found a suspect...it will even on an active am station will almost completely blank out the station the noise is so strong.  As I drive away I the noise reduces but I I can hear it all the way to my house...it's still loude but not stong enough to blank out an active station... And is about 5 houses up the road from me.... It sounds like my noise problem but it's in the direct opposite heading of the noise source my beam picks up...it's also at the point where my car drives under power lines, the same ones with the suspect pole.  So the power line can be radiating the source at that point...

The only way I will know for sure is with a portable beam and point it at the house. This noise is so strong at a certain point driving past the house that I am confident it will show up on vhf am.

I suspect it's either their a/c or their water heater for the pool..they are both right where the signal is strongest BUT again... power lines run behind the home and those points are the closest I can get my car to the suspect house... (or the neighbor..)

I will be away and when I get back this is my project with the power company.  Hopefully they are easy to work with --- PSEG On Long Island.

Thanks
All..

I will keep the thread updated as this progresses..
« Last Edit: April 30, 2014, 04:54:34 AM by KD2CJJ » Logged

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Mike
KD2CJJ
NK7Z
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Posts: 799


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« Reply #13 on: April 30, 2014, 05:43:12 AM »


I looked up ultrasonic detectors and they are crazy expensive from what I can see... out of my price range for this issue...


I did a review of a very well priced one, in kit form here:
http://nk7z.net/ultrasonic-listening-device/
I have the latest version, and it works better than the reviewed one.  About the same cost. 
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Thanks,
Dave
For reviews and setups see: http://www.nk7z.net
KD2CJJ
Member

Posts: 369




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« Reply #14 on: April 30, 2014, 06:20:47 AM »

Dave,

I read your review - and enjoy your blog very much!

Do these detectors work on noises that are not specific to powerline noise?  Such as a noisy switching power supplies located in someone else's house?

The price is still kind of high for my taste... MFJ makes one that's right at my tolerance - though we all know about MFJ quality.  http://www.dxengineering.com/parts/mfj-5008

Thanks

Mike, KD2CJJ


I looked up ultrasonic detectors and they are crazy expensive from what I can see... out of my price range for this issue...


I did a review of a very well priced one, in kit form here:
http://nk7z.net/ultrasonic-listening-device/
I have the latest version, and it works better than the reviewed one.  About the same cost. 
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73

Mike
KD2CJJ
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