Hi Kirk,
The term I use is "flooding" not swamping.
Most commonly the culprit is an unprotected solid state device connected
to an AC power wiring within about 5-10 wavelengths of an intense RF
source. The solid state device produces intense harmonic energy modulated
by broadband buzz (AC power harmonics) re-radiated by the AC power
wiring.
The same effect can occur with solid state devices connected to
computer networks operating in an intense RF field.
Like any RFI, the best approach is methodical direction finding rather than
guesswork.
73
Frank
W3LPL
----- Original Message -----
From: "K4RO Kirk Pickering" <k4ro@k4ro.net>
To: cq-contest@contesting.com
Sent: Wednesday, July 24, 2019 10:05:56 PM
Subject: Re: [CQ-Contest] SO2R interference help update
Hi Dan,
Thanks for the many CWT QSOs.
If you are willing to download a 53MB PowerPoint file, take a look at
the brief MP4 movies on page 17 of the slide show at the link below. It
demonstrates what I've heard W3LPL call "swamping". In my case, it's a
circuit which contains some kind of junction which makes a mess on 20
when transmitting on 40. I still have not been able to identify the root
cause. I just shut off the breaker when operating SO2R. The mp4 files
show how killing the breaker reduced the QRM from S9+ to S0. In the
videos, I am transmitting on 40 meters while receiving on 20 meters.
During a recent multi op here (WPX CW) our team discovered that a
seal-a-meal kitchen appliance was doing the same thing. It's on a
different circuit, and not related to the above swamping issue. The real
kicker was that it only caused QRM if used within the previous hour!
Something to do with the thermal sealing element, we suspect. The point
is that it can be ANYTHING. You'll probably have to start at the breaker
box. SO2R troubleshooting is a bit more complicated since you must have
a receiver and a transmitter running simultaneously to troubleshoot.
http://www.k4ro.net/k4ro/Single-Op-W4DXCC-2016/Single-Op.ppt
Good luck with your hunting.
73, --Kirk
On 7/24/2019 1:44 PM, Dan wrote:
> TNX to all who responded. I have a sense of direction and will begin
> diagnosing.
>
> So far I have transmitted on 40 into a dummy load connected with a short
> cable with Radio 1 (K3) and listened on 20 with the 1000MP on the tribander.
> Turning the rotator seems to indicate the harmonic is coming from the shack.
> Now I will be checking all cable and connectors, unplugging all wall warts
> and eliminating any antenna switches in the path of the tribander. Probing
> with my Tecsun SW on the harmonic has not revealed any true peaks on any
> piece of gear so far but I’m just starting.
>
> If I have a revelation and/or some success I’ll repost with my results.
>
> As an aside I’m making a flow chart to show all antennas and switching for
> future reference. Amazing how much “stuff” gets added over the years!
>
> 73 Dan W8CAR
_______________________________________________
CQ-Contest mailing list
CQ-Contest@contesting.com
http://lists.contesting.com/mailman/listinfo/cq-contest
_______________________________________________
CQ-Contest mailing list
CQ-Contest@contesting.com
http://lists.contesting.com/mailman/listinfo/cq-contest
|