[RFI] Followup - RE: RF resistant TV, DVD, & Surround Sound ?

Ed - K0iL k0il@arrl.net" <k0il@arrl.net
Sun, 22 Dec 2002 19:28:37 -0600

I also thought the same thing about those in-store distribution amps; 
they're usually DC-light with no selectivity.  When digital & HDTV units 
first came in to a local Mega-mart here, the distribution system was so 
poor that the digital signals were unwatchable unless you liked seeing 
goofy little squares all over the place.  I'd rather watch static. (They're 
Here!)  The TVs that reacted may've been the ones closest to the amps. 
 Unless you isolated the TV sets from these distribution systems, there's 
no telling what factor was in play with any TVI experienced.

Also, strong, extremely close nearby VHF/UHF signals might cause TVI (and 
how often will that really be a problem?) while HF signals from an outside 
antenna might not.  And vice versa.

The only way to really tell if there's going to be a problem "at home" is 
to hook it up at home and see what happens.  If it reacts severely, take it 
back for exchange.  It it don't, it's a keeper!  If it's somewhat in 
between those extremes, move things around a bit and add filters to see 
what happens, then take it back if nothing changes.  That's what I've done 
in the past.

Now when it comes to computer monitors, an in-store HF rcv test is a good 
start....but that's another story already told before...Merry Curistmas!

73, de ed -K0iL

On Saturday, 21 December, 2002 7:46 PM, Bill Turner 
[SMTP:w7ti@dslextreme.com] wrote:
> On Sat, 21 Dec 2002 18:33:04 -0500, Bert Rollen - K4AR wrote:
> >The effects varied widely in the stores. Some TV's were effected from 
> >10', while their neighbors showed no symptoms.
> _________________________________________________________
> I question the usefulness of this in a real-life situation.  In
> your in-store experiment, the amount of RF energy picked up by
> each TV is highly dependent on the feedline it is connected to
> and the proximity of your HT to any distribution amplifiers or
> other system components.  I used to do TV service for a lot of
> the major TV dealers in the Los Angeles area, and I can assure
> you their signal distribution systems leave a LOT to be desired.
> The phrase "minimum bid" comes to mind.  :-)
> It's quite likely that the TV with the most reaction in the store
> may simply have the worst cable feeding it.  The basic idea of
> your test is good, but there are too many variables in the way
> you conducted it.
> 73, Bill W7TI