[mythtv-users] pvr150

Brian Wood beww at beww.org
Thu Jun 26 02:55:50 UTC 2008

On Wednesday 25 June 2008 20:07:23 Raphael wrote:

> Used to be somewhat the opposite of that, and may still be in a few
> places actually. As in, when I had comcast five years ago, nothing was
> encrypted - it all came down the line in analog form, and to stop you
> from viewing channels you hadn't paid for they simply had filters on the
> line. Since channels correspond to certain frequencies they literally
> just filtered them out of the signal. When I got HBO, Stars, etc., all
> those premium channels that are now all normally encrypted, they simply
> removed the corresponding filter. The signal that came through was
> analog (thus unencrypted) and could be freely recorded with a PVR150. No
> STB was needed to view those, I just had the cable plugged right into
> the back of my TV.
> Maybe if you have analog only cable and ask to order premium channels
> without an STB this could still be possible. Probably wishful thinking.
> raphy

Such systems are very rare these days, negative trapping, where you get a trap 
if you DO NOT subscribe, as opposed to positive trapping, where you get a 
trap is you DO subscribe.

Positive systems could be easily defeated, the trap was a narrow notch that 
notched out an interfering carrier. People used lengths of twinlead with a 
piece of foil for tuning to beat them.

Negative trapping systems were harder to beat, but costly in terms of gear and 

The most interesting traps were the ones made by Vitek, they looked  lust like 
a short length of RG-6, but would trap out a single channel or group of 
channels, very low profile, but they were subject to drifting with large 
temperature changes.

Cable companies today have pretty well gone to STBs for security, especially 
once they figured out the STB could be a "profit center". Traps can alsobe 
problematical with two-way systems, which just all are now in order to be 
able to provide internet service.


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