Patrick,
Ah, if only it were that simple. I could suggest that you borrow (or rent)
one of the new generation portable, battery-powered spectrum analyzers and
take it with you when you shop, but in reality, it probably would only
alert you to real "screamers" - those sets with lots of ugly radiated
emissions. In the end, I believe (and suggest) that the best approach is
to buy your set only from a dealer who will give you a return and/or
exchange privilege if you are not happy or the set causes RFI to your
station.
Why do I say this? Mainly because of all of the variables that can exist
between the store set-up and your particular installation. Yes, the sets
that emit the most RF are most likely to be unusable in a ham's household.
But ... even the "quiet" sets could be problems. Consider:
1. Where will you place the TV relative to your antennas? (The
probability of coupling RFI into your radios from set-to-set is low. You
are much more likely to couple into any antennas that are placed over or
near the TV.)
2. How many interfaces will be connected to the TV? (TV antenna or
cable/satellite box, game box, DVR, VCR [some of us still have and use
them!], computer, stereo system, etc. The back panel of today's TV sets is
often one big jack field. I can't stand to see empty sockets, so I tend to
plug stuff into those sockets.)
3. Will the TV share any interfaces with equipment in your ham shack?
(That would be a fine way to couple RFI into the ham gear without involving
an antenna.)
All of the above are variables that can affect the end result of a given
set in a given installation. For example, I am sitting in front of my 19"
Toshiba LCD HDTV that I use as both a TV and as my computer monitor. It is
not in my shack, but I do have a 2m HT with me most of the time because I
am trustee of the local 2m repeater. That machine is on 145.39 MHz output.
When I installed the TV set, all was well until I connected the VGA monitor
cable to it from the computer (which is a Dell desktop). I found that with
the TV OFF, I had birdies that would pop the squelch on the HT. As soon as
I switch the TV ON, all goes quiet and I have no interference to the HT.
Go figure! I also have a DVD player and a stereo amplifier connected to
the set. No problems with or without those units connected.
Incidentally, the birdies on 145.39 MHz actually originate from my Ethernet
LAN. The HT is not affected unless I bring its antenna to within about 2
feet of the unshielded Cat5E cable that carries the LAN. However, with the
TV off and the VGA cable connected to the rear jack of the TV, the birdies
affect the HT to a distance of at least 3 feet. As soon as the set goes
active, no problem.
It is variables such as these why I suggest the "return option" when you
buy a set. I feel that it is more practical than hauling equipment around
when shopping. You can use the comments made on this list as a good way to
avoid the worst of the known noisy sets. Many have been mentioned during
the past couple of years.
73, Dale
WA9ENA
> [Original Message]
> From: W4PV <w4pv@comcast.net>
> To: <rfi@contesting.com>
> Date: 11/13/2010 11:35:32
> Subject: [RFI] Plasma TV's
>
> Hello,
>
> I have read many e-mails extolling the RFI cleanness of LED televisions
and how poor the shielding is on Plasma TV's. How can I determine if a
perspective television produces RFI before I purchase it. Is their a
device that a ham could afford that would sniff out a potential RFI problem
in one or more of the particular TV's of choice?
>
> Thank You,
>
> Patrick, W4PV
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