[mythtv-users] RF interf. gen. computer -- offtopic

papenfuss at juneau.me.vt.edu papenfuss at juneau.me.vt.edu
Tue Mar 2 11:34:57 EST 2004


> Also, is your house grounded?  Many older houses have a three prong 
> outlet, but the third prong doesn't go anywhere because there's no 
> 3-wire wiring in the wall.  Someone along the years may have replaced 
> the 2 prong wall outlets with three prong, leaving the ground 
> disconnected.  Proper grounding will take care of many noise problems.
> 
> Now if I could just get rid of the interference generated by my 27" TV. 
>   If things aren't _just_ right, my LIRC serial remote picks up enough 
> interference to scramble the signal.  Well, actually, what it does is 
> feeds random numbers constantly to the port even with no IR present.  If 
> I turn the TV off it goes away, and the amount of white in the screen 
> affects the amount of interference.  If I set the remote sensor just 
> right the problem goes away.  And no amount of ferrite core helped the 
> problem, I tried.
> 
> -Tony

	Ferrite won't do crap on 60 Hz ground problems.  At least not without 
many hundreds of pounds of it... :)

	If it's a ground loop on the RF cable, however, putting a ferrite
transformer will isolate two systems.  I've used two 75->300 converters
(remember those?) together as 75->300->75 to get rid of ground loops... works
great.  

	There are a couple of resons for the ground loops.  TV cable is not
necessarily grounded at the same single point as the rest of the house.  Also,
voltage drops on the power wires thoughout the house can cause ground loops.

	If the interference is RF (i.e. NOT 60 Hz), it's probably tough to find 
be fairly easy to fix.  If it is 60 Hz, it's probably easy to tell, but tough 
to fix.

-Cory

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