New CB Problems

Yay! I'm not sure how you did it, unless you managed to find a mounting point to which you were able to find enough places to make ground bonds.
I held off awhile as the posts kinda flew and bounced around, wanting to see how it would turn out.
A couple of things to remember: While a 102-108" (varies a little, but usually just called a 102") whip is a full-length quarter wave whip near the CB frequencies, it will only be a perfect match when it is worked against either an adequate ground, or some amount or reactance is added in via a tuner, proximity to metal, or a matching network, whether designed or accidental. How efficiently it works, however, may not be at all related to the SWR; you could put a dummy load at the end of your coax, show a 1:1 SWR (a "perfect match"), and still not radiate 100 ft with a stock radio. But since you've got a real antenna up there, give it a try, both at rest and while in motion. Also see if the SWR changes radically while you're in motion. An 8-ft steel whip will move around a fair bit with wind drag, so if it changes its distance to big metallic surfaces as you move, the capacitance it "sees" will change, affecting its impedance. If the SWR *does* go up drastically when you move, you may have to use something to limit how far the whip can swing.
An earlier reference to an SWR of 2.9 wasting 85% of your power was off by a smidge. It's just under 25%. So a stock (4 watt) CB would still be radiating just about 3 watts out of the antenna. Some fancier radios have "foldback" protection circuits that start to limit their output power when they sense reflected power above a certain threshold. But the only ones I'm aware of that have "power protection diodes" have them on the receiver input circuits, rather than the transmitter, to protect the first RF amplifier stage from incoming signals that are stronger than 0.7 volts, like from having a high powered mobile key up right alongside them on the highway. Ham gear manufacturers seemed to learn that once they started putting transmitters and receivers together in the same box, and stopped using tubes -- the new rigs could no longer tolerate impedances of 2,000 or 3,000 ohm antennas like we'd been feeding merrily for years, so the makers had to antenna-proof the radios.
If you get a chance, please post a picture of what you ended up with for your final antenna and its mount; I know I was starting to get lost along the way.
And as for that shop that told you that you needed to tilt your antenna back, *away* from your non-metallic cab so that it would work better? I think he was just hoping that at some point he'd stop hearing from you, as it sounds like he ran out of logical answers pretty early on.
Hope your experimenting has been useful, and will come in handy if something goes awry down the road.
73,
Handlebar

 

I agree, pictures would be good when you get the time.

 

Just to clarify for anyone lurking who is not familiar with cb radio installations. When people refer to grounding the antenna, I believe they are really talking about bonding. Bonding is connecting the large metal components of the truck together for RF [radio frequency] purposes to create one large antenna ground plane. It has nothing to do with electrical grounding.
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The general idea is to use short lengths of wire (10 to 14 gauge) or grounding strap to connect from one large metal component to another. The more large metal components [door, truck cab and truck chassis] that are interconnected the better the antenna ground plane will be. Do NOT run one long wire from the frame directly to the antenna mount because it will act like a second antenna and it will not greatly increase your antenna ground plane.
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It is preferrable that you use a multimeter[volt ohm meter] and check the resistance from the outside of the antenna mount to an unpainted bolt on the door. If not zero, run a wire from the antenna mount to an upper bolt that mounts the door to the upper door hinge.
.Next check the resistance from the antenna mount to the door frame. If not zero, run a wire from the upper bolt that mounts the door to the upper door hinge to the bolt that mounts the upper hinge to the door frame.
.Finally, check the resistance from the antenna mount to the chassis of the truck. If not zero, run a wire from the lower bolt that mounts the upper hinge to the door frame to the upper bolt that mounts the lower hinge to the door frame. Also run a wire from the truck cab to the chassis.
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Just to be clear, when you are using a single antenna setup, you must use 50 ohm coax to connect the radio to the antenna mount. If you are using a one antenna setup, do NOT use RG59 coax. No matter which 50 ohm coax you use there will be some loss of signal when using coax. Some have lower signal loss than others. For example: RG8 will lose 0.22 % of the signal for each foot of length. RG58 will lose 0.34 % per foot and LMR 400 will lose 0.14% per foot. Therefore, it is to your advantage to use shorter lengths of coax to connect the radio to the antenna mount.
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Newer trucks use a system of connecting sections of coax together using junction points. Nice idea but works very poorly for getting the cb radio connected to the antenna. While it may be quite ugly, you could avoid the original trucks setup entirely and run a short length of coax from the the antenna mount through the driver's window or vent window, if it even has a vent window, directly to the radio. Just do not completely close the window so you do not crush your coax and create still another problem.
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Not to pick on the original poster but 35 feet of RG 8 coax has a 7.70% loss of signal. A 6 foot length of RG8 coax has a 1.32% loss of signal or 1/6th the loss of 35 feet of coax. Shorter lenghts of coax are less expensive as well.

 

I sat in a friends 2005, 387 the other day. They are not entirely made of plastic. The cab and doors are aluminum. Open the doors and look at the frame of the door and you will see very tidy aluminum welds. Look at the door hinges, there are bolts holding them on, those bolts go into aluminum. The cab walls are aluminum, look at the vertical seam just rear of the door. Those two panels are likely spot welded where they turn inward. A fiberglass seam would not look like that. It would look like the seam on the roof cap of a Cascadia The roof cap is some kind of composite (fiberglass?).

 

Did you scratch off the paint to test the ground? It won't ground through paint. A self tapping screw and a loop terminal in a discrete location would do it.

 

this is what I have been telling him.and it sounds like it worked.