Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!dali.cs.montana.edu!milton!amigo
From: amigo@milton.u.washington.edu (The Friend)
Newsgroups: sci.electronics
Subject: Re: Cable
Message-ID: <1991Jun5.013530.29854@milton.u.washington.edu>
Date: 5 Jun 91 01:35:30 GMT
References: <1991Jun3.044218.16908@milton.u.washington.edu> <1991Jun3.132526.67@cmkrnl.uucp>
Organization: University of Washington
Lines: 53

jeh@cmkrnl.uucp writes:

>In article <1991Jun3.044218.16908@milton.u.washington.edu>,
> amigo@milton.u.washington.edu (The Friend) writes:
>>      Also in #2, can the technician actually see what channel a TV is on?
>> The spec sheet on a RF detector only says it can pick up "mid band TV" - 
>> meaning it (I think) finds only leakage (bad connections, extras, etc).

>there are several ways this can be done in theory.  

>For example, when a tv set is tuned to a particular channel, the local 
>oscillator in its tuner will be set to about 4.5 MHz higher (assuming 
>that tv tuners still work the way they used to, and that the IF is still 
>4.5 MHz).  

>Another interesting idea is to pick up the hash that is radiated by the 
>set's scanning circuits.  The 60 Hz vertical scan is well-modulated into
>this hash (put an ordinary AM radio near an operating tv set and you'll 
>get a sample).  Now, the different stations carried on the cable are
>NOT gen-locked to one another.  One could pick the 60 Hz out of the set's
>leakage and compare its phase with that of each signal on the cable to tell
>which station was being watched.  


     Yeah - I can see how that could work.. but typical cable companies
run junction boxes every pole or so (for multiple houses). Unless they
specifically were at the pole and tapped into your line it'd be impossible
to tell what exact house is doing what. 
     It doesn't work so nicely for descramblers though that "tune" to the
FM carrier for their programming information. These have to bounce back
information I believe (an ID code) to be recognized by the cable computer.
If the ID doesn't match, I'd guess the cable computer would alert someone
that there's an illegal box on-line. They'd still have a tough time finding
it.. it'd just be an illegal ID coded box that kept getting turn-off
 notification from the cable computer.
     One thing that would be interesting though is to tap into the FM carrier
with a PC (using a A/D converter of course). After sequential sampling,
I'd think you could draw some kind of picture as to how the system works. You
could pull a dirty one on the cable company by then rebroadcasting information
on the FM carrier (with a FM broadcaster & a D/A from the PC)... such that
you could allow full access to yourself/everyone on the cable line 
(there's little security about it if you get it working right). I got the
 idea for this one off the cable article - but the hassel of doing it isn't
 worth it in the long run... 



     
-- 
                                      ///
       Scott Rowin                   ///  amigo@milton.u.washington.edu
       ***********                  /// 
 - SPACE OPEN FOR LEASE -      \-\_///    Amigas really do it better...