🚀 go-pugleaf

ra1d+@andrew.cmu.edu (Robert L. Armitage) writes:

>I thought they just added a "noise" signal that a simple
>band-pass filter could eliminate.

>I'm sure if I'm wrong, some one will "enlighten" us .....    :-)

You're right.  Some cable companies use a narrow band noise signal to
jam the 'premium' service, and a band-reject filter will eliminate it.

(Not that I would ever actually BUILD one of these, mind you, but if I had
I would have used a 100 ohm pot, a 150 pf variable cap, two coils
consisting of four turns of #20 wire wound on a 1/4 inch form, loosely
spaced... and I would have made a "pi" filter with the two coils and one
capacitor, tying the bottoms of the coils together to the wiper of the
pot and grounding another of the pot's terminals.  This would have been
to adjust the bandwidth of the notch thus hypothetically created.)

There are other schemes, which I have never been sophisticated enough to
understand or defeat, but which are nonetheless beatable.  About the
slickest system I heard of uses a decoder box capable of decrypting the
signal in some ridiculously large number of ways.  (This will sound
familiar to most unix buffs!)  Every so often a 'newcode' control message
comes in, causing the box to automatically adjust to a new code.
Followups to alt.cable-tv.tech.myths :-)

Okay, someone else pick this up!

					David