Ground Plane and SWR help needed

[Jungleman]

Moving the antenna isn't an option, this is where I want it I'm afraid. My SWR is pegged. I ran a ground wire from the bracket to the frame, didn't help. I don't completely understand what I need to get a better ground plane, after all the bed and cab are steel right under or beside the antenna. I'm using an RG8X 18ft coax as well, and the antenna is new. Any help is appreciated. Thank you.

[MDYoungblood]

Hello Jungleman and welcome to the forum.
First thing is if the antenna mount is attached to metal, a ground wire to the frame isn't necessary but do check to make sure the bed has at least one good ground strap to the frame.
Next is to check to see if the mount is correctly installed. You didn't say the type of mount or the make of antenna.
If the mount is a stud type, look at the placement of the plastic washers, typically the problem is they are installed wrong and the stud is grounded.You should also check the coax, even brand new, the center conductor could be shorted.
These are just a couple things that might be wrong, come back with the make of the antenna and the type of mount and you will get some more responses.

3's

Greg

[Jungleman]

I'm sorry, I'm still trying to figure out how to use the tools here, and upload a picture. I have a stainless marine mount bolted to the front side corner of a fiberglass truck cap. I unhooked the ground wire I'd ran, and the SWR came down about halfway. I'll see if I can upload a picture. Meanwhile what else can I do to get it down further?

[Jungleman]

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[Windwalker]

Jungleman Hello !

It is also almost always bettter to mount the antenna on the top of the vehicle. Further it is mounted to that fibreglass cap. Historically Firestick antennas or similar ones dont perform very well and are hard to tune with poor receive. That said I personally would go with a 1/4 wave whip type antenna mounted up top even if on a magnet mount.

[Jungleman]

Jungleman Hello !

It is also almost always bettter to mount the antenna on the top of the vehicle. Further it is mounted to that fibreglass cap. Historically Firestick antennas or similar ones dont perform very well and are hard to tune with poor receive. That said I personally would go with a 1/4 wave whip type antenna mounted up top even if on a magnet mount.

I need a way to improve the plane where it is mounted, moving is not an option. there has to be a way to fix it. Thank you

[Windwalker]

You might not be able to create a reflective ground plane with that fiberglass cap for a mount. Where you have the antenna is on the side of the mounting surface to boot. Maybe you can improve your swr by playing with the length of the coax and trying to tune the tip of that antenna.

[443 Arizona]

if your willing to buy a new antenner, there is a type that has a built in ground plane, typically used on boats, its a dipole design, and made by shakespeare.
otherwise, your going to have to create a groundplane of sorts, or change to a longwire design. follow MD's advice first and then tell us what is going on.

hmm, i just saw your pix, and one solution would be to run a ground wire from the mount to a ground, that will actually become your groundplane but give you some bad performance,(bad design=bad performance)
i see this same thing on trail jeeps alot,(mounted to the side of plastic roofs and running short firesticks,) on that application their a line-of-sight use and thats it . their radios usually sound bad too because of the high swr and spurious static from the vehicle

[MDYoungblood]

Looking at the pic, the mount is only "grounded" by the coax so the coax is acting like counterpoise. Add a wire from a bolt on the mount inside the cap to the bed, this may help but there will be some capacitance.
FireStik antennas are made long because the manufacturer doesn't know what the application will be, so my guess is it is too long. You stated the SWR was totally high, check it after adding the wire mentioned, if it is still high, determine which way the antenna needs to go, longer or shorter. To make it longer you can add a stud nut or 2 if needed, shortening is pop the cap off the antenna and clip a little off the wire, do a 1/4 inch at a time.
Because of the way it is mounted and the position on the vehicle, getting a perfect SWR is unlikely but try to get at least a 1.5 to 1 on your most frequently used channel.

3's

Greg