Vehicle Antenna

FRS / GMRS Radios
1

I posted this on the GMRS subreddit, where some of you may also post, so this may seem like something you just read.

I’m new to GMRS radios (my last real radio experience was with the PRC 77).

I’ve entered this area sort of accidentally as a long time ago I picked up a couple of old Cobra handheld “walkie talkies” and more recently went to a couple of better Motorola handhelds. I wanted to be able to communicate with those from my vehicles, so I recently picked up a Midland MXT115 at a local store and got my license. I meant to get the MXT400 on the assumption that the more watts the better. The MXT115 works really well with the Motorola’s and I’m getting decent range out of them, clear reception out to at least four miles, and on one odd occasion made contact at at least fifteen miles. I’m in an area that’s very hilly or even mountainous by some definitions.

I’ve looked here and elsewhere and it seems like antennas are the real key for range. I’m using a MXTA26 6db 32" antenna on a Jeep, with it mounted to a wind fairing so that its as high on the Jeep as it can get. I’m going to add a second antenna to a Dodge 3500 and was more or less thinking of going with the same antenna, but I’ll confess my memory of radio antennas is pretty impacted by the old whip antennas used for Jeep mounts for the old PRC 77.

What antenna for a 4x4 vehicle would people recommend here?

2

Larsen NMO mount, Larsen antenna for the frequency you desire.
Mount it in the middle of the roof… I use magnetic mounts when ever possible for temporary situations. it needs a ground plane to radiate properly, not just a metal tab that holds it in the air.

3

Hi @Yeoman. The MXTA26 is an excellent antenna by Midland that works exclusively with GMRS frequencies. It tends to be our #1 recommendation for GMRS, especially when using the Midland MicroMobile GMRS radios. In regards to mounts, a magnet mount may be the way to go in your case. I would recommend looking at the MXTA12 magnet mount on our website. It comes included with the NMO base, and 12ft of RG-58 cable attached, so it’s a true “plug and play” solution for your setup.

4

Can’t recommend a specific radio antenna but would suggest a very ‘flexible’ one. I’d also suggest finding a convenient hill to do the transmitting from. :slight_smile:

5

I would be very careful using these. Mine burned/bubbled the paint on my Jeep hood using the MXT400 Midland (Twice). Had no idea that would would happen.

6

On vehicles of separate chassis construction, the best mounting system often is to make an offset mast connected physically and electrically to the chassis. Then mount the antenna so it uses the mast to raise/clear bodywork and it’s radial/ground connection goes to the mast. That’s effective on Marconi types(those mostly used in mobile vertical types, that are tuned against an unbalanced ground).

It bypasses all the usual issues of getting a good ground connection as you’ll be using the vehicle’s true common rail by design on negative earth electrics vehicles.

It doesn’t have to a huge mast, as long as it’s fractionally taller than the vehicle’s height will be a starter setup you can alter as needed. And a good design allows quick removal and/or the ability to compact it down when the radio is not actively in use.

7

As for antenna recommendations, it’s about getting the most effective suitable type not which makes or sources that matters.

For outdoor use, where being out in the sticks usage matters, where legal for your radio service use, a colinear makes a lot of sense even where TX power is limited and mobile usage is desired both on the move and for static/portable station use.

Next to that, for true mobile use, a true half wave type. Quarter wave types are really only preferred for notably ‘local’ range use (not that they can’t be effective used for distance mind).

At VHF (high band) like commonly used in older systems, half wave verticals are the practical middle compromise between compact and effective. When you head into UHF upwards, pretty much any vertical type is fair game, subject to license restricted usage, as physical constraints defining the true electrical resonant length start becoming less of a liability.

So, within the limits of types permitted and practical, go with the best practical non-coil-loaded option is where I’d go.

For static/portable use, where you deploy it when you need it and leave deployed until you move on, whatever you can legally get away with practically works. So on a sectioned carbon fibre mast, a dipole or fully formed colinear is where you’d want to go for full omnidirectional coverage. Whilst a dipole isn’t true omnidirectional, the span of it’s EM nodes are pretty close to giving near omnidirectional coverage.

But as I say, once you hit UHF upwards, within license limits, almost any type becomes manageable and practical and easily hand built or adapted from an existing other usage variant of the type.

When it comes to UHF, a minimal antenna system can go a long way flexibility wise, so I favour UHF band range radio systems for portable/mobile firstly. At SHF, everything becomes minimal impact unless you work with really high gain (I’m talking 20-30db + passive gain territory) antennas (which is usually beams and parabolic types).

So use whatever you can legally use that’s practical and maximises passively turning as much TX output into usable effective EIRP (vertical ground-reference focused) or ERP for dipoles and other balanced types.