Wireless Tower Panels

they could be used for other than cellular signal frequencies, maybe like a CB signal

 

Gernally, there are 2 different types of panels

Longer, skinnier panels are usually 1900 mHz panels. Mostly used exclusively by Sprint and T-Mobile, as well as in combination with 800 mHz panels for Verizon and AT&T.
Shorter, fatter panels are usually 800 mHz panels.

Here is a PERFECT example (just note that 99% of the time, panels will not be marked like they are in this picture):

 

Even some of the 1900 carrier's like T-Mobile and Metro PCS are now using bulkier panels. Sprint is the only carrier that still uses the very thin and tall panels around here these days. Not sure why the other's have switched styles like that.

 

Good question. You can't really tell much about an antenna just by looking at it. Taller antenna pannels generally have a narrower beamwidth than shorter ones. In the US Andrew is a big antenna producer for cellular. You can browse some products and specs here:

http://awapps.commscope.com/catalog/andrew/product.aspx?id=76&searchBSA=true

HBW= Hozizontal Beamwidth. Notice the longer antennas (2m) have a narrower beamwidth (65°) compared to shorter antennas (1m) that have wider beamwidths (85°). A narrower beamwidth allows you to focus where the signal goes better. Think of a flashlight beam.

...in Europe Kathrein is the largest antenna maker:

KATHREIN-Werke KG, Antennas for mobile communication

Operators usually upgrade their antennas only when they are really old (ie: not cross polarized) or if they are adding new technologies (ie: dual-band). Otherwise they just leave them there until they rot, since it's an extra cost for the operator