Mobile Antennas, Part 1

by Ramon Gandia, AL7X 2/23/2013

See also Part 2 and Part 3

The other day I was sitting at the Polar Cafe, and Bruce Tungwenuk KL0OT came in and asked me about a "mag mount" for his pickup.

No problem, I thought.

But then, I got to looking at various mobile antennas, to see what is out there ... besides Mag Mounted ones.

My search took me to the MARC and BA-MARC sites. These are the Motorcycle Amateur Radio Club sites, and they have quite a bit of information concerning putting antennas on Motorcycles (and trucks too)!

Magmounts are not very useful in Motorcycles, but many antennas can be put on a mag mount if you purchase the magnet/mount separately from the antenna.


There are three types of mountings.

(1) 3/8-24 stud mount. Like used on those 9 ft tall whips CB'ers use. Amateur HF mobile antennas frequently use this mount too. Not very common for VHF, or four our purposes here in Nome. Basically the antenna ends in a threaded stud with 3/8-24 threads, and the mount accepts that. You are on your own here, I am not an expert on them.

(2) NMO mounts. Pioneered by Motorola, and 99% of all police cars, etc., you see out there will have this mount. By the way, MMO stands for New MOtorola mount.

Basically the antenna ends in a one inch female thread. The Automobile (or the magmount) have the male counterpart. Look at the picture on the left.

If mounted on the roof of a car, the mount is very low profile, maybe a quarter inch above the roof. When the antenna is screwed on, thre is an o-ring type of gasket that seals the whole shebang from rain, etc.

If you look carefully, you will see that there is a large nut with outside threads. There are flats to grip a wrench and to tighten it. The o-ring is beneath this nut. The center piece is part of the mount, and the two dimples are to put a spanner wrench to hold it while the big nut is tightened.

The antenna itself fits like a cup over this mount, and screws on that threaded nut. Often it has a gasket of its own. Notice the center conductor of the coax ends in a single contact at the center of the mount, surrounded by white teflon or plastic.

The advantage of this mount is the size. It spreads the load out on your roof so things dont twist and break. This type of mount generally runs about $15 - $35 and includes the coax. It requires you to drill a 3/4" hole in the roof of the car.

The usual mount comes with the coax connector NOT installed, and the antenna can be wormed into the 3/4 hole from outside the car, thus you do not need to get to the underside of the roof. You would have to drill carefully not to go thru your headliner, but once you do, start pushing in the coax, and fish it up inside the car. Everthing is tightened up from the outside.

The NMO mount was made to be strong and easy to install from the outside. Speeds up installation in vehicles.

(3) The UHF mount. This is basically a coax receptacle mouunted to the roof of the car. There are numerous variants of this mount. Some are good, and some not so good.

I have one of the good ones in my Jeep; I do not think you can break it. It comes in a bracket that sandwiches between my tail lamp and the body. The bracket simply has a hole for the coax socket. The coax socket itself is very nice assembly with big shoulders and washers and nuts that spread the load. The coax came with a two piece coax plug.

This coax plug is nifty. The end on the cable is an SMA male plug that will go thru a 3/8 hole. Once fished through, the main sma to PL-259 the connector is screwed on to the end of the coax and you now have a full size plug to go into your mobile radio. Neat. A bit spendy, but worth every dime. This particular mount and setup is every bit as strong as the NMO.

I should also mention that the SMA male (without the adapter) will plug right into a modern Yaesu HT.

Others I have seen have smaller nuts, no shoulders, and upon hitting a branch or something will twist your car roof or even pull out.


When you decide to mount a mobile antenna on a vehicle, decide first what type of mount is acceptable to you. The NMO or a good UHF PL259 type.

My next article will show you the best places to put an antenna on a vehicle, and discuss available antennas.

Copyright © 2013, Ramon Gandia, all rights reserved.