Yes, the modem router and a second router in the granny unit both run on
AC power, so they were off. There is no wired LAN to either the
computer or the K4 -- both connect to the Internet via Wi-Fi.
Alan N1AL
On 6/7/22 17:41, Ron wrote:
Sounds like wired LAN noise. Did you shut down your router and any switches as
well as any device connected to the LAN?
Ron
N6IE
www.N6IE.com
Member:
ARRL
Redwood Empire DX Assn.
Northern California Contest Club
Northern California DX Foundation
DXCC Honor Roll - 337/345
Society of Broadcast Engineers
-----Original Message-----
From: elecraft...@groups.io <elecraft...@groups.io> On Behalf Of Al N1AL
Sent: Tuesday, June 7, 2022 4:22 PM
To: Elecraft Discussion List <elecraft@mailman.qth.net>; elecraft...@groups.io
Subject: [Elecraft-K4] I need a Sherlock Holmes (weird spurs on 40m)
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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