Hi Mark,
I understand your concern with the actual range of the Motorola T5000. Being UHF radios, they are severely limited by any obstruction in between, be it trees, buildings, hills, foliage, terrain and any others that would block "line of sight". Additionally due to the inherent design restrictions imposed on these radios, the FRS channels are limited to pushing out 0.5 watts making the GMRS channels better choice since the radio will be transmitting at 1 watt. To my knowledge, channels 8 - 14 are FRS only.
Possible things you can try to improve transmit distance are:
1. use AA Alkaline batteries instead of the rechargeable ones;
2. disable or minimize settings of interference eliminators, Quiet Talk, noise filters, coded squelch or CTCSS;
3. replace the stub antenna with a
Larsen Quarter wave. You may need to install a BNC mount to accommodate the Larsen. Incidentally, this will also improve the receive range and not only the transmit.
Hope this be of initial help/idea. Pls post back how things turned up or should you need additional information.
Good luck and kind regards.
Thank you for using FixYa.