Why is it that KOPB, 95.1 fm is licensed to Portland, but KOPB-AM, 1600 is licensed to Eugene? I could understand it if Portland and Eugene were Urban/Suburban counterparts of the same physical area, but it takes 2 hours to drive from one to the other.

There is no regulation the same call letters have to be in the same markets between the AM and FM band. However, in most cases that would make sense for the branding of the calls. I would suspect that in this case it is advantageous for "Oregon Public Broadcasting" to be in Oregon's two largest markets.

CBS took advantage of the new rule in Los Angeles, placing KCBS-TV in place of KNXT and KCBS-FM for KNX-FM. KCBS-AM remains in San Francisco.

I think it used to be that call letters were not shared in another market until about 12 to 15 years ago or so. (Someone chime in if you know for sure!)

When I got here in 1991, Channel 10 in Phoenix was known as KTSP (and KOOL-TV long before that), but desired a change in call letters to go along with an imaging campaign (they've long since abandoned)...To go along with "The Spirit of Arizona," they got permission from a radio station in Marana/Tucson, 580/KSAZ, and applied for and received KSAZ-TV as their licensed callsign.

Today, I believe the callsign is unique to the band...there is only one KXXX(AM), KXXX-FM, and KXXX-TV, but they could be in three different markets!

Couldn't there also be a KXXX-LP, KXXX-CA; and right now KXXX-DT, KXXX-DC, KXXX-LD?

KXXX-VOR (VHF signal for aircraft) and KXXX airport ID (Portland, OR is KPDX)