[TenTec] strange QRM/QRN/RFI source?

Larry Greenberg larrylg at sbcglobal.net
Thu May 15 22:14:40 EDT 2003


Over the years I have been involved in curing things causing QRM -mostly public utilities.  Advice: if you locacte the problem emphisise the terrible noise in things like  radios tvs and phones.. Don't talk about ham gear unless absoutly necessary.  I have given you advice -from experience. Ham problems seem to complicate solutions.  I still remember having to get a Motarola Tech (a WA5) to photogragh graphs from a $30k spectrem analyzer. And send with a formal complaint to  The FCC; because a cable co.refused to fix a leaky transponder that kept keying a local repeater.  To make matters worse two meter traffic was broadcast all over HBO!    The power co was rough too but when the bad and leaky transformer was killing my receiver on HF.  I complained that it "tore up" my tv reception and a crew with leak detectors was out within 48 hours. 
wb5jnc at juno.com wrote:
Greetings all,

(First, my apologies for the length of this post, but I wanted to give as much info as possible in the hope of tracking down whatever we are hearing. TNX.)

I'd like to enlist the aid of the "brainpower" of this group in identifying the source of some strange QRM/QRN/RFI that has shown up in the past few days at my QTH. It all started Monday night when my XYL asked me what she was hearing on the AM BC band. She's a KC Royals baseball fan (the result of having grown up on a Kansas dairy farm) and one of the Royals stations she usually listens to is on 690 KHz. I started investigating and we discovered that the signal was also showing up around 830-840, 970 (+/-), etc. as well. I went through the routine of checking everything in the house -- no computers, etc. on -- and even flipped the main breaker for a few seconds (the interference was still there). I also did some "sniffing" with an AM portable radio and the signal seemed to be strongest around both the electrical outlets and telephone jacks, making me think that is how the interference is coming in (both power and phone are aerial and obviously in close proximity).

I also checked and found the signal on 160M at around 1800, 1935, 2070, and 2215. (I say "around" because it was 6 KHz or so wide and seemed to vary in bandwidth.) It sounds like some sort of data stream; perhaps the best way I can think of to describe it is that it sounds similar to a slow scan signal. I'm calculating that the fundamental is in the 138-139 KHZ range based on the spacing of the signals.

At this point I'm wondering if possibly this is a DSL system at a neighbor's house gone haywire (as there are DSL channels in the 138-139 KHz range), but if any of you have any better answers, I'd like to hear them.

TNX/73, Al

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