>>coin+tD
In my experience, it was fairly common for there to be (as an example) a channel 3 and a channel 5 but no 4, so if you were flipping through the channels on certain TV's you'd see static.
>>boombo+FH
Yes, in broadcast (over the air) TV, only every other channel was allocated in a given area. That's why most devices that connected to a TV (computers, VCRs, etc.) could use either channel 3 or channel 4 because one of the two would be unused.
>>SoftTa+AN
There were some exceptions, though, as the VHF TV channels aren't all contiguous. In North America, there's a gap between channels 4 and 5; and channels 6 and 7 are separated by the bands for several radio services (FM, aviation, amateur, and marine).
>>SoftTa+6G1
ISTR we had 2,4,5,9,11, and 30 (UHF). Channels 2-5 were ABC, CBS, and NBC. Channel 9 was PBS, and 11 and 30 were local stations that weren't affiliated with any of the major networks.