mark (01/11/83)
For what it's worth, here in Columbus, our cable TV company ("Coaxial
Communications", we aren't in the QUBE area) uses three (!) different
kinds of protection. HBO is broadcast on channel 2, with a filter in
the line if you don't pay for it. (We're in an underground wiring
area, so there is no pole to climb to access the cable TV box.)
The movie channel is broadcast "scrambled" on channel 17, and clear
on channel 23. They give you a switch box that only goes up to
channel 22 unless you have paid for the extra channels from 23 up.
(I understand they are phasing out the clear TMC - when
we moved they replaced our box that went up to 39 with a box that
only goes up to 22, with channels 2-13 on our VHF tuner and 14-22
on the box sitting on top of the TV. If we had remote control we
could use it for ch 2-13, but since we don't, we wear out our
mechanical tuner even though we have cable!)
By the way, for those of you who think QUBE is neat and wish you
could get it (it's the system with feedback from the viewer) be
warned that there are nasties involved. QUBE bills you for each
movie you actually watch, even if you only watch a small portion!
I've seen complaints in the local "Action Line" column about people
being billed for movies they didn't watch, and Warner Amex is much
less cheerful about fixing mistakes on the bill than your local
phone company. Action line is a real heavyweight, but was unable
to get QUBE to change its mind.she (01/11/83)
I subscribe to TKR Cable in central NJ, and they do *not* scramble their pay stations. I assume that they trap them at the the taps, which in our case are in pedastals (not on poles), so I wonder how secure they really are. On the other hand, it's got to be cheaper for the company to make a change than with taps on telephone poles, so they probably save money in the long run.
sdo (01/11/83)
In Hillsborough, NJ, the cable company started scrambling the pay channels this week. The only way they controlled it before was to program the cable box not to be able to select the channels. I could receive them on a cable ready tuner without any problem. What people were doing to cheat the company was to only purchase the middle of the three consecutive pay channels. When that one was tuned to appear on channel three of the TV, the other two could be received on channels 2 and 4. They were just downconverting by a fixed amount, and not filtering all but channel 3 out. Now, you can only descramble the selected channel. Another annoying thing they do is to detune all the VHF channels. Cable ready TVs now have wider AFCs to capture the detuned signals, but I have to retune my TV if I want to watch the cable directly with no converter box. Scott Orshan Bell Labs Piscataway 201-981-3064 houxm!u1100a!sdo
karn (01/12/83)
Someone mentioned that cable TV companies offset their channels; this is actually done in order to improve video quality, not to intentionally make it harder for people to fine-tune their sets. This scheme is called Harmonically Related Carrier (HRC). As its name implies, each video carrier is a harmonic of a base 6 mhz oscillator at the cable company. Since standard TV channels have their video carriers 1.25 mhz up from a frequency divisible by 6 (except VHF channels 5 & 6), the cable companies have to shift everything down by 1.25 mhz from the standard on-air frequencies in order to make HRC work. For example, on-air channel 2 has its video carrier at 55.25 mhz, while an HRC cable system has it at 54.0 mhz. The idea behind HRC is that intermodulation products between signals that are generated by the line amplifiers are less objectionable because they tend to fall directly on top of other video carriers. They can often get several more video channels on a system in this way, where the distortion would otherwise be intolerable. Phil Karn