Now, on my modern TV with the remote control that displays the channel on the picture tube says channel 57, surely I’m getting the same channel that I would have gotten on that old TV from my childhood if I turned the UHF dial to channel 57. THere was no such thing as Cable TV back then. So why do I need a “cable ready” TV to get channel 57 through channel 60 as you claim in your post?
The broadcast channels and the cable channels, although they appear to be the same channel numbering system, are actually on different frequencies. That's why you have to specify whether you are setting your channels up for broadcast or for cable when you set up your TV. The broadcast channels are divided into two -- VHF and UHF. The VHF channels are ch 2 through ch 13 and the UHF are ch 14 through ch 61 (the higher ones you may remember from when you were younger were taken away from TV broadcasters to use that radio space for cell phones). VHF channels go from 54 MHz (ch 2) to 88 MHz (ch 6) and then skip the FM band at 88-108 MHz and aircraft frequencies from 108-137 MHz and other stuff then start again at 216 MHz (ch 13) then there's a really big gap and UHF picks up at 460 MHz (ch 14) and goes step by step to 890 MHz (ch 61). That was to accommodate all kinds of stuff that use the 216 MHz to 460 MHz range from more aircraft to police radios to who knows what. Since cable services are confined to the cable they won't interfere with those services. So the cable companies instead of skipping both those little and big gaps, go ahead and use those frequencies. They keep channels 2-13 on the same frequencies as broadcast TV, but shoehorn in ch 14 to ch 22 in the little VHF gap (cable ch 14 is now on 120 MHz and cable ch 22 is on 168 MHz). And then they pick up the frequencies right after broadcast ch 13 and keep on going on the frequencies the broadcast can't use. Cable ch 23 starts at 216 MHz and goes up step by step as high as the system can handle (typically 61 channels ending at 450 MHz).
So your broadcast TV (or a cable ready TV set up for broadcast channels) will look for channel 57 at 728 MHz. A cable ready TV set to cable channel 57 will look for it at 420 MHz. So that's why you can't tune in those amateur TV stations using a non-cable ready TV. It simply won't receive those frequencies from 420 to 450 MHz.
Wow, that was long. Here's a handy chart. Hope that helps.
Correction: “VHF channels go from 54 MHz (ch 2) to 88 MHz (ch 6) and then skip the FM band at 88-108 MHz and aircraft frequencies from 108-137 MHz and other stuff then start again at 216 MHz (ch 13)”
That should read: “VHF channels go from 54 MHz (ch 2) to 88 MHz (ch 6) and then skip the FM band at 88-108 MHz and aircraft frequencies from 108-137 MHz and other stuff then start again at 174 MHz (ch 7) and go up to 216 MHz (ch 13).”
Somehow that part in the middle got deleted out when I was editing. Cheers!