[Elecraft] LCD TV Causing RFI

[Jim Brown]

On 1/29/2011 9:40 PM, Brian - N5BCN wrote:
> The offending TV is not close to the shack: TV is on the first floor, shack
> on the second floor (on the opposite side of the house), antenna in the
> attic.

REPEAT AFTER ME -- IT DOESN'T MATTER WHERE THE SHACK IS, IT'S THE ANTENNAS!

Whatever trash the TV is generating is conducted from the TV to the 
CABLES that are connected to it -- power, antenna (or CATV), DVR, audio 
-- and RADIATED by those cables to your ham ANTENNAS.   It can also be 
radiated directly from wiring inside the TV if it is poorly shielded, or 
poorly designed.

> The TV is using cable with a DVR.

RF trash radiated by the CABLES can be killed by winding multiple turns 
of each cable through it's own #31 ferrite core.  Ferrite cores come in 
many sizes to fit cables of various sizes, and to allow the needed 
number of turns.  You'll need about 5 turns through a core to optimize 
the suppression on 20M, and that suppression will be pretty effective 
from at least 40M up to 10M.  The #31 material is made only by 
Fair-Rite, an excellent US company that makes the vast majority of 
ferrite materials used by hams.

For a tutorial discussion of all this, and specific recommendations for 
parts to buy and how to wind the chokes, see 
http://audiosystemsgroup.com/RFI-Ham.pdf

FWIW -- it is VERY rare for LCD TVs to cause RFI to ham gear, and the 
major Korean brands have a pretty good reputation in that regard. This 
is only the second report I've seen, and RFI is one of my specialties. 
:)   Please let us know the exact model number so that we can post it to 
the RFI email reflector.

73, Jim Brown K9YC