I might add that GMRS has tolerances as far as frequency that are far lower then most HAM gear. With GMRS being smack in the middle of the part 90 portion of the band it is important to maintain some type of standard as to not cause interference to the adjacent service. Requiring a type accepted and certified transmitter is the best way to do this. Posted this again just to be clear, I am a HAM but use part 90 gear for UHF and VHF. If the chart below posts you will see that typical HAM banded gear can allow error rates as high as 10ppm, With GMRS being a wide band service in the middle of the narrow banded part part 90 service its important to use certified transmitters. I have had plenty of HAM gear on my Aeroflex 2975, very little would pass 2.5ppm tolerance. http://mwgmrs.com/mygmrs/error.jpg