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

[jerry]

On 40M I see noise every 15 kHz.  It's constant.  Sometimes stronger, 
sometimes
weaker, but it's always there.  The pattern is obvious on the waterfall 
display.
When I tune in one of the peaks, it sounds like a rhythmic grinding.

                 - Jerry KF6VB



On 2022-06-07 16:59, Alan Bloom wrote:
> The weird thing about these spurs is how clean and stable they are.
> Switching power supply noise is generally not frequency-stable and it
> is not a clean CW carrier.  This one is actually TWO clean carriers,
> separated by about 150 Hz.
> 
> Alan N1AL
> 
> 
> On 6/7/22 17:43, Fred Jensen wrote:
>> 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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