[Elecraft] OT Mystery QRM Help (Video)

[Fred Townsend]

Gentlemen: 
That is not a dirty signal. It's very clean with about a 2 KHz wide SSB. The sidebands are very clean. I'd say you have a beacon or some other intentionally caused signal. It may be modulated by some grey line effect but the pulses are consistent as I can tell hearing only 4.  

73
Fred, AE6QL
-----Original Message-----
From: Elecraft [mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Barry LaZar
Sent: Friday, January 22, 2016 7:52 PM
To: David Ahrendts; elecraft at mailman.qth.net
Subject: Re: [Elecraft] OT Mystery QRM Help (Video)

David,
     I'm going to make a wild guess based on an experience I had about 10 or so years ago. See if there is a commercial establishment not too far away that has an external air handler as a part of its HVAC system. Some of these used solid state controllers that weren't too clean. You may have one near by. In my case, it took a while to find it and get it fixed. First, we needed to figure out what it was and next where it was. 
Figuring out what it was was the hardest as no one had ever seen this before. And, the way we found it was by eliminating all other possible sources. I wish that you have less trouble locating your problem than we had.

73,
Barry
K3NDM

------ Original Message ------
From: "David Ahrendts" <davidahrendts at me.com>
To: "elecraft at mailman.qth.net" <elecraft at mailman.qth.net>
Sent: 1/22/2016 9:16:36 PM
Subject: [Elecraft] OT Mystery QRM Help (Video)

>Stumped. Need your guesses. What is this mystery, rhythmically pulsing, 
>urban S7 QRM:  https://vimeo.com/152779708 
><https://vimeo.com/152779708>
>
>Factors: captured 5:30pm Friday (Sunset was 5:15). Densely packed Los 
>Angeles neighborhood — could be next door or a block away. Occurs 
>regularly at night or near dusk and not prime 20M day time. Occurs only 
>on 20M. I’ve noticed it from Fall on to current Winter time.  Seems to 
>be a mechanical device (pool pump?). 60-degrees falling to 50-degrees 
>tonight -- a heater system? Eventually just fizzles away slowly.
>Elecraft K3S + P3, SteppIR DB-11.
>
>David A., KK6DA (formerly KC0XT), LA
>
>
>
>David Ahrendts davidahrendts at me.com
>
>
>
>
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