Best way to mount a HAM radio antenna

[sdnative]

OK gurus, what is the best way to mount an antenna on a vehicle. I am really only concerned about a dual-band (2m/440) ham antenna. I know most of have recommended drilling the roof and installing a permanent mount. Is that the general consensus for best performance?

Currently I have a diamond 1/2 wave (normal use) and a comet 1/4 wave shorty (for tight trails and general off-road use), both NMO mounts. Right now they are mounted via a mag mount in the center of my roof. It seems to work pretty well, but I always wonder if I can do better.

How much better is a permanent roof-top install?

What types of mounts are available?

Pictures of the installed mount?

[raYGunn]

I don't know how HAM antenna are different from CB but I have a magnetic CB mount on my roof and it's always getting knocked over by tree limbs and making me stop and put it back up. My permanent solution for this one will be getting an antenna off the back but someday, if I keep hanging around here soaking up the smarts, I might need a HAM set up too.

[cruiserlarry]

There are many good ways to mount a radio transmission antenna, regardless of the frequency being used. In general, a large ground plane will improve the performance - that is why a permanent mount in the middle of a metal roof works very well, and is what you'll see on most police / public service vehicles. The magnetic mount antennas work well, too, but are more limited as you increase the power output of the radio.

A roof mount also depends (all mounts depend, actually) on what stuff might interfere with transmission:
roof racks, accessories, lights, can all create situations that compromise antenna performance. For ham radio, check out Diamond mounts - they make all types of bolt on mounts, from door lip to mirror mount, to increase your choices. But your NMO mount, put permanently in the roof, with no metal / fiberglass structures to interfere, work great.

Best to have a radio installation specialist check out your vehicle to offer suggestions specific to your situation...

[DaveK]

Rule 1- mount it as high as possible. The higher that you mount the antenna on your vehicle the better your transmission and reception will be. The higher that the antenna is above the highest part of the vehicle, the better the performance will be.

Rule 2 - get a good ground plane when ever possible.



If you are going to mount it to a bumper, tire carrier, or other object that has no real ground plane, look for antennas that are meant to be used without a ground plane. In either case get it as high as possible.

High antennas tend to be knocked of by low lying stuff like trees and the like. Ollie, notamog and (I think) Larry have solved this problem with a motorized antenna that folds flat at the push of a button. Or if they forget to push the button, its automatic when they hit a tree.

A cheaper solution, requiring no input, is a spring. When my roof rack was built, I had them put an antenna mount on the rack itself. See pics below. Both systems work well.

[sdnative]

Thanks guys,

My mag mount seems to work well, but it's not grounded. I was wondering how much better performance would be if I driller the roof and grounded it to the roof? I guess what I'm asking is how much benefit is it to have the antenna physically grounded to the metal roof? Either way, the permanent mount and the current mag mount would be in the same position respective to the vehicle (center of the roof at the same height).

Larry made this comment on another thread. That's what got me thinking:

Cutting holes in the roof is FUN !!!

I can't remember the last vehicle I owned that didn't have several holes in the roof for wiring of one sort or another... the trick is doing it correctly and neatly, and checking for clearances and wire run paths BEFORE you start drilling the holes - prep, prep, PREP !!!

One thing to motivate you is the awesome transmission / reception advantage you'll have with the flat steel roof as a huge ground plane.

Is that advantage simply because it is located on the roof, or does the permanent mount have something to do with it? Again, the permanent mount and the current mag mount would be in the same position respective to the vehicle (center of the roof at the same height).

[cruiserlarry]

My mag mount seems to work well, but it's not grounded.

Is that advantage simply because it is located on the roof, or does the permanent mount have something to do with it? Again, the permanent mount and the current mag mount would be in the same position respective to the vehicle (center of the roof at the same height).

You answered your own question. The permanent mount is grounded to the roof with a large ground plane. The magnetic mount is just stuck on the roof because it's metal (although the roof still acts as a kind of reflector for the antenna)

[BruisedFJ]

DaveK, great antenae mount, but that roof rack - SWEET! As I say to my wife, "Nice rack!"

[unwiredadventures]

OK gurus, what is the best way to mount an antenna on a vehicle. I am really only concerned about a dual-band (2m/440) ham antenna. I know most of have recommended drilling the roof and installing a permanent mount. Is that the general consensus for best performance?

Drilling a hole in the center of the roof is ideal for mounting any two way radio antenna. If that is not possible. Make sure the antenna you buy is designed to work without a ground plane. The two antennas mounted to the hatch of my Land Cruiser are designed to work without a ground plane.



If you are mounting an HF antenna, I recommend spending lots of time reading this website.

[brentbba]

OK gurus, what is the best way to mount an antenna on a vehicle. I am really only concerned about a dual-band (2m/440) ham antenna. I know most of have recommended drilling the roof and installing a permanent mount. Is that the general consensus for best performance?

Drilling a hole in the center of the roof is ideal for mounting any two way radio antenna. If that is not possible. Make sure the antenna you buy is designed to work without a ground plane. The two antennas mounted to the hatch of my Land Cruiser are designed to work without a ground plane.



If you are mounting an HF antenna, I recommend spending lots of time reading this website.

Four antennas? Looks like you're using the Diamond K-900 hatch mount for two of them. I'm also running the same mount with a Comet SBB-7 for road use and Comet SBB-1 for trail use. Both work very well.

[sdnative]

I finally decided to drill my roof, if I can successfully drop the headliner. I want to install about 4 NMO mounts (maybe 3 NMO and a 3/8"-24 for CB). I want to run a couple of ham, a cell phone, and a CB antenna.

I have a few questions related to the installation, and a couple of general questions:

1. What should the arrangement and spacing be? I have a sunroof, so I will be limited the rear half of the roof.

2. I want an easy way to remove or fold down the antennas for low clearance areas (like my garage). I am not sure if it is practical to unscrew the antenna every time. Currently I have a mag mount and just lay it on it's side. How do you all handle this?

3. I was told that the Larsen mounts are the best. Is this the general consensus?

4. How much weight/force can these mounts handle? The mount seems pretty small, and I have a hard time believing it can hold my diamond 770 at 80 mph.

5. On the mag mount I have now, the threaded connection between the mount and antenna gets very sticky (bare metal on metal), and is very difficult to unscrew. Can I use some kind of waterproof conductive lubricant on the threads to allow it to be unscrewed easily (graphite, lithium grease, other)? Something like this:
http://www.mgchemicals.com/products/846 ... 7d23a7ecda

7. If I add a roof rack in the future, how will it affect performance? Can I remount the antennas on the rack with a short extension jumper and ground strap?

8. Is it worthwhile to install a cell phone antenna? Any experience here?


I'm sure I am forgetting something, but this is enough to get me started.

Thanks for all the help.