Originally Posted by Desert Hawk
The former Cox Cable in Bakersfield was doing an electronic audit in the mid 80s. They detected what they thought was an extra tv set hooked up to limited basic service (pre 1993 cable companies could charge per tv set for limited basic). The police came to the house in the middle of the night and demanded to search the house, claiming that the results of the electronic audit was probable cause for the search. The search revealed that the "extra tv" was a VCR connected to a tv that was legitimately subscribed. Therefore no charges were filed, but if it had been an unauthorized extra tv hooked up then the people would have been arrested for cable theft. I don't know how it is possible, but supposedly cable technicians can detect how many devices are hooked up, as well as illegal descrambler boxes, from the pole using an oscilloscope or something to detect electronic backwash generated by every device. Does anyone know how this works?
They were using a Time-Domain-Reflectometer, or TDR. There may have been other technical means used in addition to that, and while other means for ascertaining a multi-device load is something I have speculated on previously, I don't think my further ruminations on the topic would be useful here. A TDR shows, on a display screen, the distance to each "imperfection " on a transmission line, and a person with some expertise at evaluating the squiggle on a TDR can spot a splitter and each end load.
The partial reregulation of 1993 alluded to by Desert Hawk was part of a "trade" of sorts, that empowered the cable companies to retain their monopoly on descrambler/decoder boxes in exchange for submitting to rental rate regulation, based on a rigid cost formula. That was when the box and remote charges on your cable bill went way down and from having round or familiar charges for cable boxes go from being charges like $4.95 a month for a box and 2.95 for a remote control, replaced by charges like $2.71 for a box and maybe $1.23 for a remote. They used to rent the remotes separate from the set top box, and while you could then buy a remote for less than 2 years rental, that option was only useful to people who wanted to have multiple remotes because if you just rented the box with no remotes, the cable company could and often would electronically disable the remote function.
It wasn't until cable companies started using 550 MHz systems that the cable band overlapped the UHF band, and it wasn't until the late 1980s or early 1990s that there was enough programming available for cable companies to use channels that overlapped the UHF spectrum. Since UHF channels are 2 MHz off the nearest cable channels, a UHF tuner would need to have an automatic fine tuning (AFT) range of 2 MHz to catch and lock onto analog cable TV "ultraband" channels.
By, I'd say, the late 1990s, every TV I serviced had over 2 MHz of capture range when set on "cable TV" and could reliably lock onto UHF channels when set in cable mode, but some didn't have that much AFT range utilized when set on UHF, probably because they assumed that the frequencies of the UHF channels were near perfect.
I remember that the Jerrold cable boxes used to develop channel 3 and 4 output frequencies that were just a little low because that was supposed to make them a little friendlier to the AGC of that era than if they were a little high, but the Sony TVs were "smart" enough to see that those outputs were out of spec, and while they would initially lock onto them, about every fifteen to twenty seconds, they would rescan their capture range looking for a closer frequency match, so in a market where I did a lot of commercial work (over half a dozen bar customers), we had to use another device, like an old 35 channel mechanical tuner box or a VCR, to interface the Jerrold Starcom outputs with the TVs.
I have scanned for digital channels with dozens of modern, cable TVs, and while only a few of those tuners would lock onto and process 8VSB signals when they were exactly "on channel", like broadcast channels 2-13, and those which I electronically frequency shifted to superband, hyperband and ultraband channels, but I have never found a single digital tuner that had the 2+ MHz of capture range that pre-digital TV tuners had.