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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