VHF/UHF Antennas - Front Bumper Mounts

[offroad_nomad]

Have any of you guys mounted your antennas on your front bumper? I'm thinking of mounting my VHF antenna on my TJM bumper with a clamp-on TJM Aerial Bracket

and a NMO mount. I'm trying to find anyone that has done something similar or uses some sort of a front bumper mount. Thanks.

 

[asteffes]

This is a slight tangent, but what is the reason for mounting an antenna to the bumper? I've found it distracting when riding in vehicles with an antenna mounted in this manner. Is it to make it easier to remove the antenna when travelling through low-hanging brush? If that's the case, why not use a rubber duck on the roof instead?

 

[Pskhaat]

I have UHF/VHF antenna on my ARB only for convenience as I'm too chicken to drill a proper hole in the roof. Bumper mounts are last resort IMO as except for maybe HF, provide a very poor groundplane for counterpoise.

I estimate a loss of 50% in performance by mounting my antenna at the ARB bar vs. trunk mounted on my commuter car.

 

[asteffes]

Why not use a magmount on the roof?

 

[offroad_nomad]

When not in use, my 4Runner is kept in our garage with my wife's car in the driveway. So I thought for convenience, I'd put the antenna with a NMO mount on the front bumper. When it can time to garage the truck, I could unscrew the antenna, screw on the NMO rain cap and drive into the garage.

Currently my CB antenna with a quick-disconnect resides on the passenger side of my front bumper. I don't even notice it now.

I'm not adverse to having an antenna on my roof with a mag mount. There isn't much available space on my roof, but I could be wrong. If you click on the link in my sig you'll see I have a roof rack, then a sun roof opening. With the rack and sunroof, where would be a good location to stick the mag mount? Thanks.

 

[Mlachica]

how about a little 12-14" antenna, is that too tall?

 

[UncleChris]

The main problem with a bumper mount is that you will have decreased performance of the antenna.

I have a Diamond K400 on my RAV4 that does a pretty good job without having to drill a hole through the roof. It clamps onto the rear door, and since it is close to the back, it is very easy to detach. It will work on doors and other places. It also has the ability to fold over with the loosening of a wingnut.

The principal problem you will experience with the bumper mount is a distinct lack of a ground plane. If you do a mount to the front bumper, take either a heavy gauge wire or coax shielding and ground the antenna mount to the vehicle ground in the engine compartment. That is supposed to improve the SWR a bit and in theory, give you a better ground plane.

 

[UncleChris]

how about a little 12-14" antenna, is that too tall?

I am running a comet rubber ducky(SBB-1) for wheeling. Since I am lazy, I have put off putting my normal antenna back on. The rubber ducky actually has pretty good performance and is pretty resilient. The Comet site http://www.cometantenna.com/products.php?CatID=1&famID=4&childID=4 has a picture of its flexibility.

It is a very good option for a rooftop.

 

[offroad_nomad]

Does the location of the roof make a difference? For optimal performance, does the antenna have to be in the center of the roof or can it be mounted towards one of the sides, up front or back? Thanks.

 

[asteffes]

The more surface area of metal under the antenna, the better a ground plane it will have. However, some is better than none, so don't sweat it if it's off-center.

 

[Mlachica]

I am running a comet rubber ducky(SBB-1) for wheeling. Since I am lazy, I have put off putting my normal antenna back on. The rubber ducky actually has pretty good performance and is pretty resilient. The Comet site http://www.cometantenna.com/products.php?CatID=1&famID=4&childID=4 has a picture of its flexibility.

It is a very good option for a rooftop.

I have a diamond nr-72bnmo 14" 2m/440 antenna. It's performance is outstanding and got really good reviews, I just can't remember the website that reviews all the ham eqpt.

 

[asteffes]

http://www.eham.net has a lot of useful reviews.

 

[asteffes]

I have a diamond nr-72bnmo 14" 2m/440 antenna. It's performance is outstanding and got really good reviews, I just can't remember the website that reviews all the ham eqpt.

I have that same antenna and would agree it's a good option.

 

[offroad_nomad]

Thanks again.

I'll need to check out the specs on that antenna to see if it Tx/Rx on 136-174 MHz.

 

[k6uk]

Ground planes and bumpers....

People often make the mistake of thinking that bumpers - especially metal ones - will provide an excellent ground plane. But unless they are welded to the frame - or properly grounded with copper strap, most bumpers are somewhat isolated from vehicle ground. Paint does act as an insolator.

So first of all we should all properly ground our metal bumpers - whether or not we are mounting antenna on them. This will increase our working ground plane, and improve performance of the antenna. Acutally while we are at it we should ground all the doors and body panels to the frame if possible. This is especially vital for HF Radios.

Now the other thing that affects our radiation pattern is where the antenna is located. Obviously the best location would be center of the roof - but often that just doesn't work out. But the closer you get the better - you will lose performance the lower you mount the antenna. But bumpers do often work well as a mount point.

One final note about bumper mounts. If you are running significant power, keep in mind that you can easily be exposing yourself to a lot of EMF radiation by positioning your antenna low. Yes the danger is real, so don't run a ton of power if you mount your antenna low. If you mount on the roof you are shielded much more effectively.

Okay... well thats all I got. Thought I would chime in.

73,

-Mike
K6UK