[Elecraft] I need a Sherlock Holmes (weird spurs on 40m)

[Fred Jensen]

I did the "Main Breaker 2-Step" and nothing went away.  My noise on 80 
and 40 on the K3/P3 is highly varied ...

1.  Narrow discrete carriers [that appear linked, 25-35 kHz apart] come 
and go, sometimes within seconds

2.  Broad [5-10 kHz] bands of noise, often without any harmonic brethren 
[that I can find] that come in pulses that look like wide-band AMTOR

3. "Rope-like" noise on the WF, with and without harmonic brethren that 
often changes in character but mainly a primary signal oscillating back 
and forth in frequency over maybe 5 kHz.

Underground utilities, but we do have a 345 kV transmission line about 
two miles away that runs from a large power plant 5 or 6 miles east to 
somewhere up in OR near the Columbia.  Sources are a mystery, but I've 
suspected harmonics of transmission line carrier-current signaling ... 
they really look like sometimes it's just idling, and then a burst of 
information.

73,

Fred ["Skip"] K6DGW
Sparks NV DM09dn
Washoe County

Alan Bloom wrote on 6/7/2022 4:21 PM:
> As part of christening my new QTH/antenna/rig here at N1AL, today I 
> did the test where I recorded all off-the-air spurious signals on all 
> bands and then threw the main circuit  breaker for the house and did 
> the measurement again, powering the K4 from a battery.  This is to 
> identify any spurs that are coming from my house so I can do further 
> sleuthing to figure out what is causing them.
>
> One spur (or set of spurs) has me mystified.  It is a series of 
> harmonics, with very stable frequencies, spaced at precisely 24 kHz, 
> that extend from roughly 6.6 MHz to 7.4 MHz.  Each spur consists of a 
> main carrier and a secondary carrier approximately 150 Hz lower in 
> frequency and approximately 8 dB lower in amplitude.  The spurs are 
> all the same amplitude, around -90 dBm (S6), dropping off as you 
> approach 6.6 or 7.4 MHz.  I don't see these spurs on any other band.
>
> The spur amplitudes did not change when I turned off AC power, so it 
> can't be the rig's switching power supply or any other electronic 
> device in the house.  It's nothing internal to the radio because if I 
> switch to a dummy antenna the spurs go away.
>
> So it's coming in through the antenna.  The antenna is a 6-band trap 
> vertical about 30 feet from the house, with the coax coming 
> underground to the shack.  We're on a large lot, there is a canyon 
> (i.e. no houses) behind the property, and there is a vacant lot on the 
> side where the antenna is located so the nearest houses in the 
> neighborhood are about 150 feet away from the antenna.
>
> The electric utility power lines switch from overhead to underground 
> at our property line, about 150 feet away from the antenna. Internet 
> is via cable, which is underground also.  Both power and Internet 
> enter at the far end of the main house, which is over 100 feet from 
> the shack, located in a granny unit.
>
> I believe the exact fundamental frequency is 7007.03 kHz / 292 = 
> 23.9967 kHz, in case that's a clue.
>
> Anyone have any ideas of what could be causing this?
>
> Alan N1AL



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