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Re: [RFI] New HDTV Purchase - What to Avoid?

To: rfi@contesting.com
Subject: Re: [RFI] New HDTV Purchase - What to Avoid?
From: Dave Cole <dave@nk7z.net>
Date: Tue, 8 Dec 2020 15:15:39 -0800
List-post: <mailto:rfi@contesting.com>
Thankfully, the "Lightening in a box" TVs are no longer made...

73, and thanks,
Dave (NK7Z)
https://www.nk7z.net
ARRL Volunteer Examiner
ARRL Technical Specialist, RFI
ARRL Asst. Director, NW Division, Technical Resources

On 12/8/20 2:55 PM, Rob Atkinson wrote:
I second the advice on taking a portable sw receiver to the store.
Around 7 years ago I took my Grundig Yachtboy receiver with me to a
Best Buy.  I didn't plan on making a purchase.  I wanted to try to ID
the source of RFI at home.  I suspected the problem was a plasma TV
next door but since I didn't know what one sounded like on 75 and 160
m. I figured I could hear one at the TV display in the store and find
out.

I extended the telescoping antenna, put the receiver on AM on some
frequency in the 160 m. ham band and began to walk around.   Much to
my surprise, most of the equipment powered on for display was
extremely quiet, at least on medium wave and 75 meters.  In fact, the
overhead fluorescent lamps generated most of the noise.   That changed
as I approached the TV area.  From about 60 feet away I heard the same
thing I had been hearing at home which became the unmistakable
signature AM sound of plasma TV RFI.  Once in the TV department the
plasmas really blasted, mostly from the screens where tiny gas tubes
with electrodes in them continually fired.  Some sets showed in-house
slide shows of fixed images.  These didn't make as much noise.  The
sets when dark between images generated much less noise.  But live
action, such as a football game whereby pixels were constantly firing
by the thousands generated the mother of all RFI.   Back then, sports
enthusiasts were nuts for plasmas because they lacked ghosting and had
zero latency.  I peered behind one through the air vents and saw that
the entire backside was nothing but heat sinks and electrolytic caps.
What a nightmare.   The other sets were LCD as I recall and they were
okay.   I hope TV technology has improved and ATSC 3.0 marks the end
of plasma TVs.

I don't know if used plasma TVs are still sold or not but yikes, don't
ever buy one or live next to one.

73

Rob
K5UJ
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