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eHam Forums => Elmers => Topic started by: KB1SNJ on November 20, 2012, 12:06:26 AM



Title: Help identify periodic QRM
Post by: KB1SNJ on November 20, 2012, 12:06:26 AM
Hey, I have a new problem. Its an "AC buzz" type sound coming through. It starts about every 2 minutes and lasts almost exactly 23 seconds. It starts gradually (comes up over about 2 or 3 seconds) but stops suddenly.

I have a G5RV and hear this on several radios across HF (My Icom 7000 Noise Blanker clears it up).

As a test, while it was buzzing I turned off each circuit breaker one by one, to no avail.

Anyone had this isssue or know how I can hunt it down? The houses are close together here. I'm thinking a power line (transformer?) issue or some equipment in a house but no idea what, or how to track it down...



Title: RE: Help identify periodic QRM
Post by: KA4POL on November 20, 2012, 01:23:27 AM
That looks like some machine being switched on regularly for a constant period.
You already excluded your home. Does it occur 24/7 or can you see some daily pattern?
You need to use some direction finding equipment. An old AM radio would do fine.
May be it's time to get into the DIY business: http://www.handi-finder.com/


Title: RE: Help identify periodic QRM
Post by: KB1SNJ on November 20, 2012, 09:58:38 AM
Well I just got up (I work nights and listen on my nights off), and no there is no QRM at the moment that I can recieve.

Thanks for the DF tip, my handheld wasnt much help last night as I dont know ehere to point it, although it has a ferrite bar inside so I guess that means the null is off each end? (Degen 1103)

I hope I can find this!   :)


Title: RE: Help identify periodic QRM
Post by: KA4POL on November 20, 2012, 10:30:52 AM
You need to find a pattern for this QRM. Just a sample, a photovoltaic array will not work during night times.
Yes, the null is where the ferrite rod ends point. So you either can use the maximum or the minimum to locate a direction. Try it outside, perhaps half a mile away, as well.


Title: RE: Help identify periodic QRM
Post by: K8AXW on November 20, 2012, 11:51:53 AM
CHRISDX:  The symptoms you describe might possibly be a bad doorbell transformer.  I had the same problem several years ago. 

When a doorbell transformer goes bad, quite often they will arc inside the windings and the cycle is similar to what you describe.  Most of the time the doorbell will continue to operate as if there isn't a problem.

After shutting off the main breaker and finding I still had the problem I notified the power company.  They sent out a truck and crew and proceeded to cut power to each house that was fed from the same dropping transformer. 

When they found the house that had the problem, they notified the residents and mentioned that they had a bad doorbell transformer and suggested they get it replaced. 

Fortunately, they promptly did and all was once again peaceful in the valley.

Oh, I would play the "illegal interference card" only if necessary.  The will be smarting a bit from having their power abruptly cut and there isn't any point in agitating them more..... until later.


Title: RE: Help identify periodic QRM
Post by: KH6AQ on November 20, 2012, 12:15:34 PM
It sounds like how someone described battery charger QRN (not QRM) he found.


Title: RE: Help identify periodic QRM
Post by: K5LXP on November 20, 2012, 01:43:55 PM
Echo KA4POL, this same kind of noise was a bad streetlight a quarter mile from my QTH.  I DF'd it with a MW receiver that had a loopstick.  Got a few bearings, then went driving around and soon was able to pick it up on the car radio.  That got me within a block of it, from there I could see the streetlight blink on and off in sync with the noise.  A call to the local utility with the pole number and a few days later it was resolved.

Mark K5LXP
Albuquerque, NM


Title: RE: Help identify periodic QRM
Post by: N4NYY on November 20, 2012, 02:24:04 PM
Chris,

You make need the help of a local radio club and foxhunt it down.


Title: RE: Help identify periodic QRM
Post by: KB1SNJ on November 20, 2012, 03:56:33 PM
OK it was not active during the day today, but now at 7pm I turned on the radio, and it's back. Interesting!


Title: RE: Help identify periodic QRM
Post by: K8AXW on November 20, 2012, 07:50:26 PM
Off daytime - On nighttime......probably street light sensor.


Title: RE: Help identify periodic QRM
Post by: KB1SNJ on November 20, 2012, 07:53:22 PM
Found it.    We have no radio club nearby that I know of but my colleague at work KO1H is president of the semi-active RI wire antenna club and very active ham, and he suggested that street lights will cycle like that. BINGO.

I set my car AM radio to a nonstation and was driving around to establish a perimeter. I got the North-South done (about 2000' total span) and headed to the next street over and the house behind mine had a flickering street light on the pole. I parked under it and sure enough when it cycled the radio went crazy for about half a minute until it gave up trying to start.

Time to call the power company...

what a relief!


Title: RE: Help identify periodic QRM
Post by: KA4POL on November 20, 2012, 10:13:43 PM
Good to hear that. By the way, some of these street lights do have photo cell switches which can be activated by a laser pointer...  ;)


Title: RE: Help identify periodic QRM
Post by: KB1SNJ on November 20, 2012, 10:23:12 PM
is there no way to edit my original post?  I wanted to add [SOLVED] to the title and cant do it...


Title: RE: Help identify periodic QRM
Post by: KA4POL on November 20, 2012, 10:26:28 PM
I once made a typing mistake, no chance. The only way is through the moderator. Just leave it and it goes down into the archives.


Title: RE: Help identify periodic QRM
Post by: N4NYY on November 21, 2012, 04:47:17 AM
Chris,

Put pressure on them. The FCC is usually pretty good against power companies, if they do not fix the problem.


Title: RE: Help identify periodic QRM
Post by: KE3WD on November 21, 2012, 06:35:48 AM
Chris,

Put pressure on them. The FCC is usually pretty good against power companies, if they do not fix the problem.

Start out with a nice friendly attitude and a phone call, though. 

Most power companies I've dealt with are very responsive to such reports and initiate repairs rather quickly. 

If the person reporting same treats them like they would like to be treated in the first place. 

Save the pressure for the rare occasion when a call or two doesn't yield a satisfactory response.


73


Title: RE: Help identify periodic QRM
Post by: N4NYY on November 21, 2012, 07:44:10 AM
Chris,

Put pressure on them. The FCC is usually pretty good against power companies, if they do not fix the problem.

Start out with a nice friendly attitude and a phone call, though. 

Most power companies I've dealt with are very responsive to such reports and initiate repairs rather quickly. 

If the person reporting same treats them like they would like to be treated in the first place. 

Save the pressure for the rare occasion when a call or two doesn't yield a satisfactory response.


73


You obviously do not live in NJ?


Title: RE: Help identify periodic QRM
Post by: KB1SNJ on November 21, 2012, 09:02:21 AM
National Grid is all over the map because they scooped up numerous utilities. Here in RI they were very slow and inefficient at responding to widespread power outages after hurricane Irene. There was a hue and cry about that and they promised to improve. Between Irene and Sandy, they created a response plan that was totally revamped. It involved placing liaisons with each police/city authority and pairing tree removal with line crews, and working that under a triage system. The improvement was dramatic and even the web site map was much more accurate after Sandy. Power was restored by Friday everywhere.

I signed onto the web site and found a nice page to report the broken street light. Got a confirmation email immediately. Then a response a few hours later. The response said I had failed to change the region from upstate NY to RI, and to re-enter. So I signed on, changed to RI, and filed the street light report. Nothing. No automated response OR human response. I had gotten both from NY.

I have National Grid gas as well, which like the electric was a bought utility. The elec company has online account info, easy bill pay and all that. The gas doesnt despite years of web promises to get them under one umbrella. Go figure.

So it appears National Grid is good at buying utilities, but operates them as a separate entity with some having better management than others. I was stunned that the NY/NJ power repairs were so slow and inefficient compared to our own. You'd think the changes they made for us would have been implemented at all their units, why not?