Sophist wrote:
I tend to remember the station numbers which I frequent, rarely the letters though.
Nickelodeon- 32
Animal Planet- 58
Turner Classic Movies- 60
A&E- 110
BBC America- 113
The Science Channel- 117
None of these channels would have call letters. Call letters are only required for stations that broadcast over the public airwaves. In the United States, station callsigns can start with K, W, A, or N (for some reason N or A are never used, and A must be followed by a letter from A to L), and can consist of three letters, four letters, or a letter followed by a two or three digit number representing the channel followed by two more letters (e.g. W48CE on channel 48 or K204GG on channel 228, a.k.a. 93.5 FM).
In Canada, callsigns must start with CF, CG, CH, CI, CJ, CK, CY, CZ, VA, VB, VC, VD, VE, VF, VG, VO, VX, VY, XJ, XK, XL, XM, XN, or XO. CB is allocated to Chile, but you may notice that CB is also used in Canada for CBC stations (e.g. CBLT). Typically TV and radio stations only use CF, CH, CI, CJ, or CK. A few stations in Newfoundland use VO, and amateur and some low-power stations use ones that start with V. For example, a now-illegal TV station in Toronto was called VX9AMK. Most callsigns in Canada are four characters long, although there are some three-letter stations owned by the CBC (CBX in Edmonton) as well as a couple stations in Manitoba (CKX-TV in Brandon). The CBC also has some five-letter stations, but they all end in "T" and are typically French stations, e.g. CBOFT.
Mexico, which allows callsigns starting with XA, XB, XC, XD, XE, XF, XG, XH, XI, 4A, 4B, 4C, 6D, 6E, 6F, 6G, 6H, 6I, and 6J, typically has callsigns ranging from 3 to 5 characters, with 5 characters being very common. XEW-TV is one of the major stations in Mexico City. Just across the border from San Diego is XHUPN-TV.