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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 12:48:25 -0500
List-post: <rfi@contesting.com">mailto:rfi@contesting.com>

When I saw you have the Toshiba 19AV600U I checked my Toshiba TV in the
shack and we have the same model.  I just tried listening to AM on the cheap
AM/FM radio that is about two feet from the TV.  I turned off the TV, tuned
in a weak AM station, then turned on the TV.  I didn't notice any change in
the received AM signal.  Also, there weren't any "sweeping" sounds.


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.  I made no analysis of the noise or its pattern, except that it
> is broadband in nature and strong across the AM BC band.  2) The other
> likely candidate could be the drivers for the CFLs that provide the
> backlight.  I did notice an upward "sweep" in frequency (as heard on the
> speaker of the radio) each time I switched on the Toshiba set.  That sweep
> lasted for perhaps 2 to 3 seconds, then stopped.  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.  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 suspect that it has been superceded by something "better" by now, but I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.  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.  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]).  If anyone does note such interference from
> a TV set or monitor, please post to the reflector with info about the
> offender.  Thanks.
> 73, Dale
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