Command truck antenna question.

[acs680]

We have a former ambulance that we are converting to a mobile command unit. Has anyone used one for this purpose, and have any insight on where to mount antennas? We will be using anywhere from 6-8 antennas but can't use the top of the box due to lack of a ground plane.


Any help and pictures would be much appreciated!

 

[gewecke]

We have a former ambulance that we are converting to a mobile command unit. Has anyone used one for this purpose, and have any insight on where to mount antennas? We will be using anywhere from 6-8 antennas but can't use the top of the box due to lack of a ground plane.


Any help and pictures would be much appreciated!

More info please? What bands,type of antennas,and why 6-8 antennas? If this for LEO or SAR use then I would think you'd have more info.
n9zas

 

[n0nhp]

Ground planes are easy on fiberglass cabs. In my install days I just went to the local metal fabrication outlet and had them cut stainless steel sheets into squares 1/4 wave on VHF Hi as all my installs were VHF/UHF/800. Have them put a slight corner to corner crimp and place a 3/4" hole in the center. Drill your 3/4" hole in the fiberglass (or larger) center the SS plate over the hole. Place a good bead of RTV all the way around the perimeter of the plate. Use self drilling screws to attach the plate, (2-3 3/4 " long per side) install the NMO style base and fish the wire.
I would attach a photo but the last time I did an install was over 10 years ago ;-) (at least other than an amateur for a friend or myself).
They worked well for construction trucks that would destroy antennas on overhead branches and obstacles so I think they should work on a modular ambi body.
The modulars I had a chance to work on usually had a cable run that was accessible from inside the unit. I would just center the plates above that run and you should be good to go.

Good Luck,
Bruce

 

[gewecke]

Yeah this is easier now,than in the past with older type 1 and type 2 ambulances. Our type 2 rigs have the sheet metal groundplane already built in to the raised roofs to accept any antennas for the hospitals or mabas radios.
n9zas

 

[DieselFF918]

The only style of ambulance that would pose a ground plane problem would be a type 2. Most type 1 and type 3 ambulance should have a metal box.

 

[comsec1]

diamond plate

I would suggest a sheet of aluminum plate cut to fit on top such as diamond plate as well as a short tubular (square) rail which would be wide enough to fit an NMO style mount, and than run all the coax through one or two holes. If this is to be used as a communication vehicle you will probably find yourself on the roof alot changing or customizing antennas and the diamond plate will be very usefull.

 

[wv8mat]

if you look at most van style ambulances you will see a 6'x6' or maybe a little bigger metal grounding plate used to put the NMO style antenna on. I have seen the both box and van style with up to 5 antennas using that method. They work wonderful.

 

[izzyj4]

Almost every Type I, II & III ambulances have some sort of antenna mounts built into the boxes on the top. Most manufactures with the Type I & III boxes have 6 points (usually) available, well at least the ones I have worked on the road with. As for the Type II "Econoline" or "Sprinter" styles I am not that familiar with.

Who was the manufacturer of the old ambulance? (ie Lifeline, Wheeled Coach, Horton, Braun, ect.)

What model year was it?

Is there any existing antennas / NMO mounts on the rear box roof now? (You can utilize them)

What frequency bands are you planning to transmit on?

 

[code3cowboy]

Which band? You can use half wave antennas and not worry about it.

 

[ramal121]

You need to look carefully and see if there is a ground plane for antenna purposes. I have done a lot of Leaders and all have had a metal screen embedded in the fiberglass for the past 15 years or more. All ambulance manufacturers realize that radios will be installed in their vehicles and provide for this. Pull off the antenna access or the cot lights and see what is up there. If there is a ground plane (screen) but no metal plate for mounting, you will have to use a thick mount and pay attention to getting the mount and screen bonded securely.