In 2017, the FCC updated the GMRS by allotting additional interstitial channels in the 467 MHz band, increased the license term from 5 to 10 years, allowed transmission of limited data applications such as text messaging and GPS location information and made other updates to the GMRS rules to reflect modern application of the service.
FCC
https://www.fcc.gov/general-mobile-radio-service-gmrs
Attitude, I mean altitude wins. First find a "real" GMRS antenna. I mean a REAL antenna. Not some Chineseium coat hanger on a refrigerator magnet pos. Do your homework and get back to us as we love to pick holes in noob purchases. (bunch of dicks around here even if they do mean well)
Place the FRS/GMRS on top of the vehicle. 462/467MHz is more or less nearly line of sight save for the magic that is UHF spill and fill radiation.
27MHz and it's neighboring frequencies. Big crew cab? It seems odd but if possible Hobson's choice is on the driver's side bed rail a couple feet aft of the cab. There is no science to this. It just seems that this is where it goes for a variety of reasons that range from drive through collisions to radiation pattern to political affiliation. (go figure) In any case it seems to be the default.
Of course the best place is the top middle of the cab. Then a 8ft whip is tall enough to to attract low flying aircraft. It hits everything. Then there is the rear bumper mount where the first three feet of the antenna sees itself reflected in the bed of the truck.
The compromised antenna on the hood. Why? Just why would you load up a 40 inch whip and expect it to do anything? Move along , nothing to see here...
The top of the diamond plate tool box in the bed mount. Sure, why not? But I guarantee it will at some point get in the way of a load or something.
Just because you didn't ask. Get some wide , flat , braid with eyelets or hooks on the ends and bond the beegeebuzzs out of the truck. Two on each door, two on the hood, extra from the engine to the frame, more from the frame to body , rear end to frame to body, front suspension to frame to body. There really is not any such thing as over kill here. Unless of course you begin to add significant weight to the truck.
now, in no particular order:
There is no such thing as an effective maggot mount antenna.
Resonance is NOT VSWR. VSWR is NOT resonance. Trim and tune for RESONANCE , you can deal with "most" VSWR issues later.
DC connections for the radio are directly to the battery. Do not pass go, do not use the cigarette lighter socket, do not use light gauge wire, grommet every feed through or there will be tears and smoke.
Despite the propensity for the membership here to deride, demean and generally trash a noob, ask. They will offer unique and usually effective solutions to equally unique problems. The wealth of experience here is such that most of us have done it wrong at least once (if not several times) and aren't shy about telling on ourselves.
Lastly:
Welcome to the asylum. The inmates have the keys.
