World Naked Bike Ride - Chicago

Collected notes and links on common CB/FRS/GMRS technologies:

http://en.wikipedia.org/wiki/Two-way_radio

CB: 40 Channels, 4 watts, 26.965-27.405 MHz, 162.400-162.550 MHz, AM modulation.
The maximum legal CB power output level, in the U.S., is four watts for AM and 12 watts (peak envelope power or "PEP") for SSB, as measured at the antenna connection on the back of the radio.
http://en.wikipedia.org/wiki/Citizens%27_band_radio

GMRS:
http://en.wikipedia.org/wiki/GMRS
5 Watt 40 Channel with Up to 30 Mile Range
Name Lower frequency (repeater output) (MHz) Upper frequency (repeater input) (MHz) Motorola convention Icom F21-GM convention Notes
"550" 462.550 467.550 Ch. 15 Ch. 1
"575" 462.575 467.575 Ch. 16 Ch. 2
"600" 462.600 467.600 Ch. 17 Ch. 3
"625" 462.625 467.625 Ch. 18 Ch. 4
"650" 462.650 467.650 Ch. 19 Ch. 5 Use not permitted near the Canadian border.
"675" 462.675 467.675 Ch. 20 Ch. 6 Suggested nationwide emergency and road information calling. Nationally recognized coded squelch for 675 emergency repeater operation is 141.3 Hz.
"700" 462.700 467.700 Ch. 21 Ch. 7 Use not permitted near the Canadian border.
"725" 462.725 467.725 Ch. 22 Ch. 8
This second set of frequencies shows the interstitial ranges shared with the Family Radio Service services. These frequencies can only be used for simplex operations.
Name Frequency (MHz) Motorola convention Icom F21-GM convention Notes
"5625" or "FRS 1" 462.5625 Ch. 1 Ch. 9
"5875" or "FRS 2" 462.5875 Ch. 2 Ch. 10
"6125" or "FRS 3" 462.6125 Ch. 3 Ch. 11
"6375" or "FRS 4" 462.6375 Ch. 4 Ch. 12
"6625" or "FRS 5" 462.6625 Ch. 5 Ch. 13
"6875" or "FRS 6" 462.6875 Ch. 6 Ch. 14
"7125" or "FRS 7" 462.7125 Ch. 7 Ch. 15

TriSquare TXS 300 ten billion channels eXRS
eXtreme Radio Service (eXRS) two-way radios use proprietary Frequency Hopping Spread Spectrum (FHSS) in the ISM band (900 MHz frequencies). This FHSS system combines the power of digital technology with narrow band FM modulation technique. Merging the two technologies facilitates a radio communications system that maintains a narrow band base signal to ensure for maximum usable range within a given dB power budget, comparable to traditional fixed frequency narrow band FM radios, but with the added benefit of wide band digital security and privacy provided by the frequency hopping spread spectrum algorithm. Maintaining the information signal as narrow band FM modulation centered on discrete frequencies allows for a large pool of non-overlapping hopping frequencies to draw upon within a given section of the radio frequency (RF) spectrum. The pseudo-random drawing of the hopping frequencies spreads the total signal power equally over the entire bandwidth of the RF spectrum used, which ensures minimal interference between many simultaneous, independent users.
Interference Free is a major advantage that eXRS has over existing FRS and GMRS radios. Based on a contracted study from the Electrical and Computer Engineering Department of a major university, more than 100,000 eXRS users within talk range can enjoy uninterrupted communications. Whereas, FRS/GMRS quickly becomes unusable with just a few tens of users within range of each other. Bottom-line is that the eXRS two-way radios provide private communications in areas where FRS/GMRS conversations can be congested or impossible.
Under the same environmental conditions and regardless of power, the TriSquare eXRS radios usable talk range will be equal to or greater than that of other portable UHF two-way radios in most cases. Coverage within steel and concrete structures should be better with eXRS radios. Multiple independent tests indicate that the eXRS products always exceeded the performance of the FRS/GMRS products advertising the longest ranges.
eXRS radios are free from any Federal Communications Commission (FCC) user licenses, can be used at any age and for any purpose (personal or business), unlike GMRS radios.
http://reviews.ebay.com/FRS-GMRS-EXRS-or-CB-WalkieTalkies_W0QQugidZ10000...

The Family Radio Service (FRS) provides a series of 14 channels in the 462 and 467 MHz range set aside by the Federal Communications Commission (FCC). FRS is a personal radio service that uses frequencies in the UHF band, and thus doesn't garner the interference effects found on CBs, cordless phones, toy Walkie Talkies and baby monitors. FRS uses FM instead of AM, and has a greater reliable range than most license-free radios. These radios are ideal for sportsmen and their families, free of interference from business and government agencies.
FRS portables use little power and are ideal for communicating with hunting partners, family members back at the campground, or for overall peace of mind. These band radios require no special license by the FCC to use and the range of use can be up to two miles. New FRS radios can be very practical for short-range communication devices that are made available to the general public.

GMRS is an acronym for the General Mobile Radio Service, which is a series of specific frequencies in the 462 MHz range set up by the FCC. Again, it depends on terrain, but these radios can have a much broader range for talk, extending up to five miles. While a bit larger than an FRS Walkie Talkie, GMRS radios will give you increased range in a unit that you can virtually take anywhere. One thing to note, however, is that to be able to use the 10 available channels on the GMRS band, you must obtain a license from the FCC. But besides that, the main difference here is that this service allows you to discuss your personal business or commercial activity. This is not your typical hobby radio. This is intended for purposeful communications only. No matter what brand they'll all be dependent on Watts to transmit. Most FRS radios are limited to 0.5 Watts, while GMRS radios are often limited to 2 Watts, yet some models can have up to 5.
Channels 1-7 are solely for use with the FRS/GMRS system. Channels 8-14 are solely for FRS and 15-22 is for GMRS. Some radios will only give you one channel option where some will give you seven. Consider a 14-channel unit if you plan to use your radio in a large, urban environment where GMRS is already popular.

Professional Mobile Radio (also known as Private Mobile Radio (PMR).
http://en.wikipedia.org/wiki/Professional_Mobile_Radio

Real World Ranges for CB, FRS, GMRS and MURS Radios
http://www.thetravelinsider.info/2003/0815.htm