[RFI] RFI from Horizonal Sweep

[michael.findley at ni.com]

Most TV's have a shield around the tube area. The "engineer's" think that a
ground wire centered on both sides is "the way to ground" any interference.
I would check this out and ferrite these wires or re-direct them vertical
to the bottom ground shield. I have seen this many times in RF interference
testing and emission testing. Also the wire to the tube can be hot RF wise.
Ferrite this to and these 2 things generally stop most all interference or
at the very least minimize it to an acceptable level.
(Embedded image moved to file: pic06359.gif)


                                                                                                                                
                      "WX5L"                                                                                                    
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                      01/06/2004 08:05                                                                                          
                      PM                                                                                                        
                                                                                                                                
                                                                                                                                




Hello,

Has anyone had success eliminating the RFI caused by the 15.75 khz
horizonal
sweep from televisions. These signals are heard as rough-ac notes every
15.75 khz. These harmonic signals carry well into the HF bands and actually
change in tone slightly as the picture changes on the screen.
Unfortunately,
some of this energy gets coupled and is backfed into the cable drop and act
as a pretty good antenna. I would think too some radiates directly from
unshielded wiring in the sweep circuit. I guess we can attribute that to
the
cost cutting measures taken to keep TV's cheap. We all suffer because of
that either with RFI ingress or RFI egress.

I have tried #77 toriods at the cable input of the TV with slight success
but still much remains.

Building a faraday cage around the set is not an option as it's a large
widescreen set.

Anyone have any success?

Thanks,

Randy
WX5L at charter.net
Thibodaux, Louisiana

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