GMRS vs CB

Now they have combination GPS/GMRS radios that can show all the vehicles in your group and their location on a topo map.

Caution, a ham is about to geek out on this topic....

GMRS and FRS share frequencies.  FRS is limited to 0.5 watt (500 milliwatts).  Its all UHF (ultra-high frequency) and FM (frequency modulation).  Most UHF capable ham radios will receive on FRS/GMRS freqs, but wont be able to transmit.  Often, you can find modifications out there for ham radios to make them transmit on freqs outside of their designed range.  But this can fry the radio, too, especially if you do not have an antenna tuned for the frequency.  For receive, you can use a bent coathanger and it wont harm the radio, but for transmit you must have an antenna "tuned" to the frequency or else the trasmitted power reflects back into the radio and will eventually fry it.  A Standing Wave Ratio (SWR) meter is used to measure this reflectivity and tune the antenna.

GMRS and FRS frequencies: http://www.gmrsfrequencies.com/gmrs-frequencies-list.html  All the GMRS/FRS is in the range of 462 megahertz (mhz), or .7meter, 70 centimeter wavelength.  Ham 70CM band is 440-444 mhz.

CB is AM (amplitude modulation), with its crappy audio and unpredictable propagation.  CB is HF (high frequency) and in the range of 27 megahertz, or about 11Meter wavelength.  CB is limited to 4 watts, but this is widely ignored, with many truckers running "kickers" of 1000 watts or more.  There is little to no policing (actually, hams are supposed to help the FCC police the airwaves) so there's lots of noise and cussing and such on CB.  And HF bounces all around, bounces off layers of the atmosphere etc - so often you can talk across the continent but not across the county.

Everyone is probably going to find GMRS much more usable and effective, especially with its more-or-less built-in Automated Position Reporting System (APRS, the capability to show locations of stations).  Also, as the linked page above shows, there are "repeaters" on GMRS - these are (usually) fixed location stations, often high on a mountaintop or commercial tower, which listen on one freq (the input freq) and xmit what they hear on a nearby freq (ie they repeat everything).  So you set your radio to listen to the repeater output freq, and transmit on the input of the repeater, and its as though you are sitting at the top of that high tower, with muuuuuch greater range.

Theres also capabilities like encoding a tone in the transmission, and everyone setting their radio to only listen for that tone (its sub-audible, so YOU dont hear the tone, but your radio does).  This can be used to block everyone on a given frequency who is not using the pre-shared tone, and squelch other groups from your conversation.

The downside is that the GMRS radio hardware is expensive compared to CB, with different coax, and antenna requirements, and technically you are required to have a license, for which there is no test, only application and fee to FCC.  You think all those drunken rap-blasting SXS fellers have licenses?  Yeah, Im sure they do.

I personally think transition to GMRS would be a good thing for RCRC....but the club should consider investing in a couple of handhelds to loan out to newbs for club rides like we did with the CBs. 

Time and technology marches on.  Keep up or get left behind.  Next we will be considering electric Jeeps, like Barbie.

Im interested in the MXT575 since it can be remote mounted.

Any radio that transmits should have a SWR* matched antenna.  The handhelds are matched prior to assembly.  If you buy the correct antenna that's MEANT for the GMRS freqs, you most likely will be able to use it without tuning without frying the radio.  A 1:1 match SWR (ideal) is pretty hard to achieve anyway.

Also, recognize that just because you can modify the radio to work on a particular frequency, doesnt mean its going to work well or last very long.  This is especially true for the handhelds - they generally have an antenna thats designed and optimized for the freq range that the radio is sold for, and if you mod the radio, its not going to match (high SWR) and can literally fry the innards of the unit.

50 watts of FM is a lot of ooomph.  I have seen a 50 watt radio do freaky things like light up idiot lights in the dash.  Most modern car owner manuals will tell you that they are designed for some maximum RF transmitted power to be installed. Yeah I know, dont try this at home, professional driver on a closed course etc etc.  You want some metallic surface area between your antenna and things like your engine computer.

I had a ham radio buddy there in Hsv with a high-wattage HF rig in his class A motorhome, and he keyed it up on I-65 the first time and his slide-out extended.....at speed.  Messy situation.

* - SWR is Standing Wave Ratio