When choosing a radio for GMRS operations, there are several things to consider. GMRS base station radios do not exist as a single component but are comprised of a mobile GMRS radio and a 13.8-volt power supply instead. Technically, any Part 95 certified GMRS mobile radio will be fully compatible with a GMRS system. These radios require very little user input to operate on repeaters and are ready to use for simplex out of the box. GMRS operators are legally limited to 50 watts of transmit power, with some radios being limited to less power output.  Signal and sound quality may vary somewhat between brands, however the biggest factor that will affect the performance of the radio is a well-matched antenna system. Common radio brands of FCC Part 95 Certified GMRS mobile radios include the following.

Midland

MXT500, MXT575, MXT275, MXT115

High-power 50W options (MXT500); "MicroMobile" compact form factors.

Wouxun

KG-1000G Plus, KG-XS20G Plus

Repeater capable; 50W (KG-1000G) and compact 20W (KG-XS20G) options.

BTECH

GMRS-50V2, GMRS-20V2

50W and 20W power levels; high frequency flexibility for monitoring.

Radioddity

DB20-G, DB25-G, DB40-G

Compact "mini-mobiles" ranging from 20W to 40W.

Retevis

RA86, RA87

20W (RA86) to 40W (RA87) output; often sold with full kits for base or mobile use.

Rugged Radios

GMR45, GMR25

Focused on off-road and overlanding; 45W and waterproof 25W versions.

An antenna system is made up of an antenna, mast or tower, feed line (coax/hardline) and possibly a ground plane kit.  An SWR meter might also be added to this list since it is the most basic tool which can be used to ensure your antenna system is matched well to the radio. The antenna system is actually the most crucial part of any GMRS base station. In fact, a radio station without an antenna system is like an automobile without an engine. It may look and feel perfect from the driver's seat, but when you step on the gas pedal it won't go anywhere at all.  As long as your radio produces the right frequency and senses your voice, it is up to the antenna system to deliver that package into the air. Making the right choices here will allow you to minimize any potential loss and maximize gain and overall performance. 

Feed Line (coaxial/hardline)

LMR-400 is a very popular choice for low loss, high quality coax, but it can be costly. Some manufacturers offer similar sounding versions like KMR-400 which are much cheaper, but extremely inferior in quality and are not worth the money saved and trouble caused. LMR-400 is a safe and sound feed line that can be used for GMRS base stations up to a max length of 100'. It is not recommended for repeater use because of the problems associated with the nature of duplexing.

 High quality connectors should also be used to minimize loss and only a minimum of connectors with no unnecessary splicers or adaptors. The overall length of the coax should be minimized as well and does not need to be cut to any particular interval. 

The antenna may very well be the single most important component in your GMRS base station. And the most important attribute of the antenna is that it is resonant on the GMRS band of frequencies. It may be tempting to try to make a non-GMRS antenna work for you out of convenience, but it's a very bad idea usually. Some antennas that are tuned for 70CM might be broad banded enough to perform decently on GMRS, but there will be somewhat of a compromise.  Just make sure to test your antenna/radio match with a VHF/UHF SWR meter to ensure safe and efficient operations.  Among GMRS base antennas, one may find a few common variables. The main considerations include antenna gain, ground plane vs no ground plane and omnidirectional vs directional. An antenna with gain has the ability to multiply the output power of your radio by a certain multiplier, effectively making your signal stronger. 

 Gain is measured in dBi (decibels relative to isotropic): Compares the antenna to a theoretical "isotropic radiator" that sends energy equally in every direction. Unity antennas have 0 or no gain but are fully omnidirectional. 

Some antennas require a ground plane kit that may be supplied with the antenna when purchased, and some antennas do not require a ground plane at all. A ground plane kit usually consists of multiple radials cut to a specific length, angled accordingly and connected to the negative ground side of the antenna/coaxial. The primary purpose of a ground plane is to act as the "missing half" of an antenna, effectively completing the electrical circuit necessary for transmission and reception.

The decision between directional and omnidirectional antennas depends on your personal purposes for your GMRS station. If your purposes are very general or you want to be able to get into your local repeater (which you can easily reach) and you want to maximize your simplex range in all directions, then you should get an omnidirectional antenna. However, if you are trying to get into a distant repeater (which is hard to reach) or even reach a particular simplex station, then you may need a directional antenna to point at your target. Either style offers options with gain up to 12 dBi or so. For reference, a 50-watt radio with an antenna that has 12 dBi gain (assuming no loss) would produce around 480-watts at the output of the antenna. This extra power makes your signal stronger and more able to overcome noise and penetrate obstructions. GMRS (UHF) signals do still depend on some line of sight between antennas, but some obstructions can be penetrated by a stronger signal.

In addition, remember that your base antenna should be outside (in most cases) and will be exposed to all of the natural elements. All external connections should be weather-proof to prevent water intrusion and corrosion which can lead to antenna system failure. Wrapping connections in electrical tape alone is insufficient and unwise. Multiple layers of truly waterproof products should be used to ensure long term preservation of external connections and to prevent damage to radio equipment.

Your new base GMRS antenna will need to be mounted to something; thats where a mast or tower may come into play. The most common and affordable choice is a mast made from some kind of steel poles which are fastened together to acheive a particular target hieght above ground. This mast could be made from fence top-rail, conduit, fiberglass or even PVC and might be mounted to the side of a house, shed or other building. One could alternatively bury the base of a mast, with a concrete base, into the ground and potentially add a system of guy wires to help support the vertical poles. One may purchase a telescoping antenna mast in one of many lengths which can be pushed up and fastened into place by one man. Aluminum flagpoles have also become a common choice to be used as a telescoping mast, but they lack the rigidity and ground continuity of a steel mast. These flagpole masts may be a good choice for those limited by a Home Owners Association since a flag can be flown on the mast below the mounted antenna which may go unnoticed. Also, these masts are easily lowered out of sight when antenna is not in use. 

Even better than a mast, if you can afford it, is an antenna tower. A tower could come in different forms but will allow for a more permanent and stable installation of multiple antennas, using vertical separation between each and more weight and wind resistance overall. A tower can be built from 10 foot sections to almost any height desired. Additional regulations may apply for towers 200 feet high and above.

On the other hand, maybe you only need a mount point for your antenna that is short and simple because your GMRS demands are very light or you are fortunately very close to a very good repeater. In cases like these, one may decide to use a very short rooftop mast, similar to those used for small satellite dishes. Or maybe it would be convenient to take advantage of a brick fireplace chimney and use a chimney mounting bracket to fasten your mast above the house. 

There are many ways that one may decide to mount an antenna and no one way is right or wrong. It depends fully on your situation and your needs or preferences. Either way you go, you'll find that most base antennas are made to be mounted to a mast. So, whether the mast is stand alone, fastened to a structure or at the top of a tower, a short or long mast will undoubtedly be part of most installations. 

There are some GMRS antennas that are considered portable and are made to be hung in a tree or otherwise. N9TAX makes some pretty good 'roll-up' Slim Jims and J-Poles that are pretty effective for portable operations, but do not have much gain. Given the characteristics of the UHF band that GMRS uses, these antennas should be kept clear from tree branches and other objects which could interfere with the transmitted signal.