Still Opening the Box

Good afternoon, I am used GMRS radios in my friends vehicles while traveling through the woods of Maine and also in different Jeeps. But this is the first one i have owned, I am still reading all about it before I install it. I plan to be able to mount it so it can be moved between my Jeep and Truck. I think i understand what i need to know to mount this, radio, but i am quickly considering a base station for my place in Maine. I have six repeaters in my region, so it would be for comms between our camp and the vehicles. I am installing a MXT575 with a 3bD Ghost Antenna in the vehicles. I am considering the MXT500 as the base with a Duracom LPK-14 power supply. My biggest questions are as follows: 1) how long or a run or drop can the coax be; 2) what is the best type of coax, there seems to be several differences; 3) what type of tuned antenna do you recommend: 4) how high should I place it?

Thank you in advance for any suggestions you can offer.


  1. Long enough to connect the radio to your antenna with a bit extra to create a service loop (in case connector ever needs replaced and to relieve antenna connector of supporting the weight of the coax if support weathers loose).

  2. For my base station I use Times Microwave LMR-400 coax. It is low loss at 2.7dB for 100 feet. So you lose nearly 1/2 the power (3dB) for 100 feet of cable at GMRS frequencies.

  3. My antenna is the Comet CA-712EFC. The SWR on it is right at 1.1 across all the channels. I have also built a 1/4-wave ground plane that worked very well, but lacked the gain of the larger antenna.

4)Mount it as high as possible. My base antenna is at 30 feet above ground with the tip at 40 feet. Just make sure it clears any utility lines should it topple in a storm. Guy it well, and ground it well.
FCC says:
§ 95.51 Antenna height.

(a) Certain antenna structures used in a GMRS system and that are more than 60.96 m (200 ft) in height, or are located near or at a public-use airport must be notified to the FAA and registered with the Commission as required by part 17 of this chapter.

Hope this helps.
73 de KJ7WUZ/WRHW845

Thank you very much, Dave

Where I want to install it is at my Maine camp and there are several repeaters in my immediate area, so I think this will help increase comms between the base camp and mobile units. Thanks again.


Interesting that you have so many repeaters. Are they actually GMRS? Seems like a high concentration…

Confused by your comment. These are Midland MicroMobile GMRS radios, their newest models with a maximum of 50watts. They are not repeaters.

Walt / WRTP426