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Enough of a ground?

B

Believer45

Member
Feb 22, 2009
7
0
11
Good evening, all. I have installed an ARE aluminum contractor cap that is 36" tall on my pickup truck, attached with four self-drilling self-tapping bolts into the top edge of the bed. There is a non-conductive seal between the cap and the bed. Is there enough contact between the cap and the bed/vehicle for a CB antenna to be mounted to the cap, or is there enough metal in the cap itself to act as a ground plane?

My radio is a 1994 Uniden PC66 with a few modifications (bigger finals, Connex echo board), I do not run a kicker. Current antenna is a Wilson 500 (I know, that is why I am asking about a replacement) magnet mount on the roof of the extended cab.
 

taking a guess , id say maybe . lol .
i guess the safest way would be to use a mfj analyzer with a mag mount tuned on another vehicle , and see if it has enough ground to be fairly close to tuning . maybe check for contiunity between the shell and the bed after its installed , maybe adding short ground straps on the corners between them . maybe just stick the antenna on there and see what a quick swr check with an external meter shows .
yep , im absolutely positively definately sure my answer is , maybe .

oh yea ... if you do wind up needing the ground straps remember they need to be to bare metal . not paint or clear coat or wax . metal to metal .

Earth Grounding Construction Materials
http://www.iceradioproducts.com/35.html
 
i dont know what a contractor cap is, but if its made of aluminum, has three self tapping screws touching the aluminum, and the screws are screwed into the metal of the bed of your truck, then you should be fine mounting a cb antenna to it.

if the antenna is within about a foot of the cab of the truck you might see an increased SWR.

antennas like to be out in the clear.

drilling a hole in your roof and mounting your antenna there will be the best.
the wilson 1000 should work well for you.

LC
 
Contractor cap is a bed topper cap that has tool boxes on both sides and a ladder rack on the roof. I cannot put a mag mount on the cap - won't stick to aluminum. Current antenna has the base load above the roof of the cab but not above the top of the cap - Lil Wil is not on the truck in the picture below but sits centered side to side about six inches from the back of the roof, close to centered on the truck.

Do you think a Wilson 1000 on the cab roof would work? I can either drill the roof or run the co-ax in by the third brake light. My concern is the base load will be below the top of the cap.

I know enough about these to know I don't know much - sorry if my questions or comments seem off.
 
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attaching an antenna to the ladder rack would be the best option for you.

maybe try one of the wilson trucker antennas.

as long as that ladder rack is grounded to the vehicle body, then it should make a great groundplane.

good luck,
LC
 
I carry ladders on the rack and need to access from both sides so attaching to the side of the rack would not work. My thought is a body mount like this one
images

attached to the front of the cap in the center with antenna mounted to it. The antenna would stick up between the ladders.
 
That should work fine and the cap being aluminum will be plenty of ground plane for an antenna by itself.

Nice to see someone else from The Diesel Stop btw (y)
 
that mount will work to physically mount the antenna, but all of that aluminum will wreak havoc with your radiation pattern and your SWR.

you need to get the radiator (whip) of the antenna above any other metal on the vehicle for it to work properly.
LC
 
loosecannon said:
that mount will work to physically mount the antenna, but all of that aluminum will wreak havoc with your radiation pattern and your SWR.

you need to get the radiator (whip) of the antenna above any other metal on the vehicle for it to work properly.
LC
Click to expand...

If I set the mount so that the base of the antenna is level with the edge of the roof of the cap and use a center load (like the Wilson 2000) then the load will be above the ladders. Would that be sufficient?
 
Expect things to not stay the same with that installation. The SWR and how the antenna works in general will vary depending on the surroundings as with any other mobile, but also with what's around that antenna that can move, as in ladders, and other tools. How close that stuff is to an antenna will have a greater/lesser affect directly connected to that "how close" thingy. If you have the option, keeping movable/removable things away from antennas is a good thing to do. Then, if you think about it, those movable/removable thingys are directly attached to the other half of that antenna, the vehicle's body. So that "how close" thingy can turn into an 'RF connection', which is just about like having a short circuit, sort of.
Does that mean you can't do it? Of course not, it's done all the time in various ways. You do have to keep in mind that things are going to change at times, certainly won't be the 'best' in the world, and "stuff" happens.
- 'Doc

(Sooner or later you'll hang that antenna with one'a them ladders. The next time you key the mic, all that power will act like a plasma-arc and cut that ladder in half! When it happens, please take pictures, I ain't never seen that happen before. You know?)
 
I have a 2006 GMC diesel with a contractors cap on the short box, with a extended cab. I have a puck mount about 18" from the back edge of the cap. I have a pred. 10k on the puck mount (single coil). Then i have three ground straps on each side, bonding the cap to the box, then i have ground straps bonding box to frame, cab to frame. I have a uniden 68xl,XForce 3 pill. The SWR is low and stable. Watching it with a Radio Shack meter and a palsar dual meter.

You may not need to do all this but it works good for me.

Pictures of truck in my album. I think they are puplic. Not very good at adding pics or links.
 
damn , it took a lot of work to get yours right , but you got it kor b . we always read about folks having to put a lot of extra effort into bonding and grounding thier stuff just to get ground for their antenna to tune . i sure am glad i dont have a vehicle/setup that needed all that extra $ and work .
 
Did you ground the linear and radio to the frame as well?
Just wondering...

If it was me; I don't run meters once I set up the station. Too many cables that can become intermittant. I like radios that have built-in SWR meter; that is usually enough to know if the SWR has changed.
But what do I know?
 

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