[comp.sys.amiga] Radio Wave Interference

kraussW@batman.moravian.EDU ( SysAdm) (09/15/89)

I have a vintage Amiga 1000 which my father uses to manage his business out
of our home.  One unfortunate thing that we have found is that if the computer
is on, the TV isn't because you can't see anything.  (Note, they don't run
cable where I live.)  SO...  Is there a reasonable way to add shielding to the 
Amiga's Interference or filter the antenna leading to the TV?  (Which is two 
Rooms/Walls away.)  Or is this a "deal with it the best you can" situation.

(Please, no suggestions like, "A Two foot lead wall ought to do the trick.") :-)

					Thanks,
						Bill Krauss
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Michael_Robert_Delany@cup.portal.com (09/22/89)

 
Many computers on the market have been known to cause RF interferance.  The
simplest protection against RF would be to make sure the system has a good 
ground -- this solution usually works well in most RF applications.  If this
doesn't solve the problem you might want to evaluate the coax and connections
on your television(s).  If you have 300 Ohm coax (twin lead) I would strongly
suggest replacing it with 75 Ohm RG/58 or 59 coax and use a splitter/matching
transformer on your tv set.  The transformer/splitter is available at most 
hardware stores, Radio Shack and if one is close, electronic surplus stores
for a couple of dollars.  Relocation of the computer also may be a solution,
if its not too much of an inconvenience, try this first if you haven't 
already.  

mgardi@watdcsu.waterloo.edu (M.Gardi - ICR) (09/24/89)

We just purchased a GE cord-less telephone.  The other day, I was
playing Leader Board golf when the phone (in another room on the same
floor) started ringing furiously.  This was no RING... RING... RING...,
but a continuous RRRRRRIIIIIIIIIINNNNNNNNNNGGGGG!.  I started checking
out  the phone but it seemed to work properly, then I noticed that the
ringing only occurred when the actual Leader Board screen was being
displayed on the Amiga.  When the game was being played, nothing
happened.  As soon as a round finished and the Board was displayed, the
phone would go nuts.  The system I'm using is a 500 with a Sub-system,
and since Leader Board is dongle protected, the dongle was inserted
properly.

Anybody have any clues as to what Leader Board might be doing when this
happens?

Joe deSousa
Mutual Life of Canada     Waterloo, Ontario
[C/O mgardi@watdcsu.waterloo.edu]
[Please include the words "Att: Joe" in the subject line of any Email replies.]

karl@sugar.hackercorp.com (Karl Lehenbauer) (09/25/89)

In article <6369@watdcsu.waterloo.edu> mgardi@watdcsu.waterloo.edu (M.Gardi - ICR) writes:
>We just purchased a GE cord-less telephone.  

>RRRRRRIIIIIIIIIINNNNNNNNNNGGGGG!.  

>...ringing only occurred when the actual Leader Board screen was being
>displayed on the Amiga....

>Anybody have any clues as to what Leader Board might be doing when this
>happens?

Congratulations, you can now page your cordless phone from your Amiga :-)
Well, the computer generates a lot of RF, and it's different based on
what it's doing.  To prove this, just get an FM radio, put it
next to your computer, and tune it until you get a bunch of noise.
Now run different programs, format floppies, etc.  Wildly different sounds.
It just happens that some combination of the program loop, data being
displayed on the screen, etc, is generating the "right" RFI at a close
enough frequency (or harmonic of the frequency) to make your rather stupid 
and unshielded (no offense) cordless phone freak out.
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bear@bucsb.UUCP (Blair M. Burtan) (09/25/89)

In article <22359@cup.portal.com> Michael_Robert_Delany@cup.portal.com writes:
>
> 
>Many computers on the market have been known to cause RF interferance.  The
>simplest protection against RF would be to make sure the system has a good 
>ground -- this solution usually works well in most RF applications.  If this
>doesn't solve the problem you might want to evaluate the coax and connections
>on your television(s).  If you have 300 Ohm coax (twin lead) I would strongly
>suggest replacing it with 75 Ohm RG/58 or 59 coax and use a splitter/matching
>transformer on your tv set.  The transformer/splitter is available at most 
>hardware stores, Radio Shack and if one is close, electronic surplus stores
>for a couple of dollars.  Relocation of the computer also may be a solution,
>if its not too much of an inconvenience, try this first if you haven't 
>already.  

If you're really ambitious, you could surround your machine with
a grounded copper mesh.  Kind of like in a microwave oven.  The only
catch is that you would be able to touch the keyboard.


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