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Re: [RFI] LCD TV wipes out AM BC band

To: svetanoff@earthlink.net
Subject: Re: [RFI] LCD TV wipes out AM BC band
From: Ken Winterling <wa2lbi@frontiernet.net>
Date: Tue, 22 Feb 2011 13:35:01 -0500
List-post: <rfi@contesting.com">mailto:rfi@contesting.com>

I do not have the set connected to a cable or antenna; I do not use it for
watching TV programs.  The set is used as a second monitor (expanded
desktop) for a laptop so there is that video cable between the set and the
laptop.  I also use the PC audio input to provide external speakers for a
second laptop adjacent to the first.  Both laptops are within 18" or less of
the TV.


On Tue, Feb 22, 2011 at 13:15, Dale Svetanoff <svetanoff@earthlink.net>wrote:

> Ken,
> Thank you for the prompt feedback.  That is very interesting and brings up
> 3 questions in my mind:  1) Does my set have a problem that is specific to
> it or which was caught by Toshiba and then fixed in production?  2) I
> suspect that your radio has lower sensitivity than does the Super Radio III.
>  To verify the concept, I'll have to drag out one of my cheapie sets and try
> the same test.  I'll report my test results here.  3) Could there be some
> sort of interaction between my set and the computer system?
> A question for you:  Do you have anything else connected to the Toshiba?
>  You would have the AC power cord, of course, but other than a coax to the
> Antenna port, anything else?  I have Audio Output (line level) going to an
> external amp, and the SVGA cable from the computer (going into Input 7).
>  The signal on the coax is from my over-the-air antenna.
> Again, thank you for doing the test.
> 73, Dale
> ----- Original Message -----
> From: Ken Winterling
> To: svetanoff@earthlink.net
> Cc: K8RI; rfi@contesting.com
> Sent: 2/22/2011 11:48:45
> Subject: Re: [RFI] LCD TV wipes out AM BC band
> Dale,
> When I saw you have the Toshiba 19AV600U I checked my Toshiba TV in the
> shack and we have the same model. Â I just tried listening to AM on the
> cheap AM/FM radio that is about two feet from the TV. Â I turned off the TV,
> tuned in a weak AM station, then turned on the TV. Â I didn't notice any
> change in the received AM signal. Â Also, there weren't any "sweeping"
> sounds.
> Ken, WA2LBI
> On Tue, Feb 22, 2011 at 12:34, Dale Svetanoff <svetanoff@earthlink.net>
> wrote:
> Roger,
> An excellent question, plus I should have included the Toshiba model info
> in my posting.
> I can think of at least two systems within the set that could be the
> noise-makers: 1) The switching power supply that operates the whole set.
> These days, it is not uncommon to have switching freqs as high as 3 (or
> more!) MHz. Â I made no analysis of the noise or its pattern, except that
> it
> is broadband in nature and strong across the AM BC band. Â 2) The other
> likely candidate could be the drivers for the CFLs that provide the
> backlight. Â I did notice an upward "sweep" in frequency (as heard on the
> speaker of the radio) each time I switched on the Toshiba set. Â That sweep
> lasted for perhaps 2 to 3 seconds, then stopped. Â My thoughts are that
> maybe the CFL drivers are "ramping" up the lamps over that period of time,
> or they are adjusting to a pre-set drive level to maintain a given
> background intensity.
> My set is the Toshiba Model 19AV600U, which seems to be a popular model. Â
> I
> suspect that it has been superceded by something "better" by now, but I
> have seen these in hospitals, motels/hotels, commercial establishments, and
> so forth. Â Remember, any set that is going to cause a problem in the
> region
> of 1 MHz or so will do so when in close proximity to the antenna of a
> victim radio. Â Since most AM BC band radios have integral antennas
> (usually
> ferrite bar or rod types - the one in the Super Radio III is a whopping
> 200mm long [nearly 8 inches]). Â If anyone does note such interference from
> a TV set or monitor, please post to the reflector with info about the
> offender. Â Thanks.
> 73, Dale
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