Writing

Software, technology, sysadmin war stories, and more. Feed
Thursday, August 2, 2012

The days of cable TV with mechanical button tuners

When you think of cable TV today, you probably take it as a given that your set-top box chats with its headend to do things. You can add channels or purchase pay-per-view movies from your remote. This gives the cable companies quite a bit of control over who sees what.

It's a big difference from some of my first experiences with cable. We had a cable box which was just a bunch of mechanical buttons, a three-position rotary switch, and a fine tuning knob turned sideways. With that rotary switch at the top position, those mechanical buttons would give you channels 2 through 13. When you picked its middle setting, you could then tune 14 through 25. The last setting gave you 26 through 37.

Whatever you selected came out of the box on channel 3. The fine tuning knob seemed to adjust the center frequencies up or down across the board. I'm not sure if it was affecting the input or output side, but it opened the door to some interesting things.

First of all, the modulator in our cable box didn't quite stop at channel 3 on its output side. Let's say you picked "20" with the rotary switch and buttons. You'd get cable channel 20 as channel 3 on its output. However, if you took your TV and flipped it to channel 4, you'd get channel 21, more or less.

Sometimes, you could then finesse the cable box's fine tuning knob to push it past 21 and towards 22. I think if you "met it halfway" by also playing with the TV's own fine tuning knob, sometimes it might work.

Basically, there were ways to tune slightly above the range of channels you were officially able to get. I guess this was before the days of "cable ready TVs", and they seemed to keep people from seeing some of the premium stuff by putting it up above channel 37. I think I actually managed to watch a movie on a premium channel one night by fiddling around like this. It took a lot of twiddling and patience, but eventually I found up seeing a channel we normally would not get.

That said, not all of their premium channels worked this way. They had HBO on 14 and Showtime on 16, and neither of them needed an addressable cable box. Instead, they used traps: inline filters which sat on the line feeding your house which took a notch out of a given spot. I suspect they had one of each if they were sold separately.

Not surprisingly, channel 15 looked like utter garbage since it was affected at both ends by the traps. I remember that they put some random throwaway channel there like a radar feed because of the relatively poor picture quality.

Another oddity in those days was that Disney was still a premium channel, and I want to say it was up on channel 7. It was scrambled, and it used a rather irritating scheme which made a horrible racket. If you were just flipping through channels and went past it, you'd wake up everyone in the house since it was so much louder than everything else.

Further complicating matters was the fact that it was on one of the precious few channels that a regular TV set could get without a cable box. This is because both broadcast and cable assignments for channels 2-13 are the same. I think they moved it to another channel later on and recycled channel 7 after receiving too many complaints about this very situation.

This kind of stuff is joining the dustbin of history right next to memories of what scrambled TV looks like (with that wavy black line and inverted colors) and good old fashioned snow when no signal is present. Cable boxes and TVs no longer have fine tuning knobs, scrambled TV just says "This channel is not available. Press OK to order.", and snow has been replaced with a blue screen which says "NO SIGNAL".

I guess that's progress in a nutshell.