My apologies to the list. I only replied to the sender and not the list.
--- Forwarded message ---
From: Dave Van Wallaghen <dave@w8fgu.com>
Date: September 13, 2018 15:34:56
Subject: Re: [RFI] Home RFI Hunting
To: jim@audiosystemsgroup.com
Thanks for the reply JIm. I doubt you would remember, but we met once in
Dayton a few years ago. I've been working in the Elecraft booth for the
last 10 years or so.
On September 13, 2018 14:23:44 Jim Brown <jim@audiosystemsgroup.com> wrote:
Several thoughts on this.
First, RF noise from defective/poorly designed equipment OFTEN travels
on the green wire, so yes, separate green wires is a good thing.
I will certainly try this. Do you think rewiring the panel to place my
shack circuit on the opposite phase from the AV circuit might help as well?
Second, chokes to kill noise currents need to be tuned to the
frequency(ies) where you are bothered by the interference. While PROBING
for noise sources at lower frequencies can be effective, there's no need
to choke those frequencies unless you use your radio there.
Although I don't have decent antennas for 630m, I would like listen in and
this noise will prohibit that. I was able to hear airport beacons over 100
mi away when I unplugged the TV.
Third, if the TV is a noise source, I would choke every cable connected
to it, starting with those that are likely to be the most effective
radiators, first the power cable and coax feeding it, then audio and
video cables if there are any.
I did. The only other cable is an HDMI connection and I was able to get 13
turns around a #31 core. I did this close to the TV but maybe I should
place one near the cable box as well.
Only if you need to kill noise on the new 630M band, and only if you
wind a lot of turns. Simply clamping one or more of them onto cables is
unlikely to do much.
I kind of thought as much - makes sense. Just thought I would ask.
I'm surprised that you're hearing a lot of noise coming from an LCD TV.
The most likely source would be a poorly filtered switch-mode power
supply built into it. I would also look for other sources around the TV,
like switch-mode wall warts for various equipment, or built into other
equipment.
Yes, I was surprised as well since I bought this to replace a satan
worshiping plasma TV ;-)
It does appear to be the PS for the TV (it generates this noise even when
turned off - just plugged in) and the supply is internal to the set. I did
unplug the other wall warts on the circuit - the cable box and a DVD
player. I do have some issues with those as well and looking for
replacements. I measured the outputs of each and they are right at 12v. So,
I think they are regulated. But, the noise is very prominent with just the
TV plugged in on that circuit.
Thanks again for the reply and I will first try the separate grounds to see
if I can reduce it some.
Take care,
Dave W8FGU
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