[Ilugc] OT - TVTuner card
- From: siva@xxxxxxxxxxx (Sivasankar Chander)
- Date: Sun May 8 09:55:56 2005
Is it advisable to connect the cable from the cable operator to the
computer's TVTuner card? What made me ask this question is a thread
in our ILUGC which discussed about ISPs, stressed not to opt for
cable ISPs, since they electrocute the PCs. Some body pls suggest.
(Please use Carriage Returns in your text - if you rely on line
wrap, it messes up formatting for lots of people.)
If you isolate the external cable electrically from the cable
you plug into the tuner card, you will obtain a measure of safety.
The easiest way to do this is to use a two-section back-to-back Balun
to convert the 75-ohm unbalanced impedance of the coax to a 300-ohm
balanced impedance suitable for a ribbon cable, and back again to
75-ohm unbalanced, suitable for coax, which can be plugged into the
TV tuner card.
Cable -> Balun-> 300-ohm Ribbon Cable -> Balun-> 75-ohm Coax -> Tuner Card
The Baluns and 300-ohm rubbon cable should be readily available at
any TV parts shop. The Baluns provide the isolation, and will save you
from garden-variety shorts with 230v and 440v mains, but it still
won't save you from a lightning strike or a short with a 11-KV HT line,
both of which have been known to happen in Madras.
Incidentally, I'm not sure if a stock DOCSIS cable modem will still work
after this isolation section is inserted, so if anybody has done this,
please post to the list to clarify (Downlink will probably work, I'm
not sure about the uplink).
-Siva
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