DIY antenna solution for fiberglass cabs

O.K. It really is a "trial and error" thing on these new trucks. Good luck!

 

Upgraded. Keep running out of parts and have to make more. Course now that this side is done, they want to switch me to an international. And start over.

 

OK, got some results. Going to dual spring put the swr a bit high on 40, but it's still fine on 1 and 19. Still using the built in meter so exact readings will have to wait. I suspect that the higher swr is from dropping it down instead of up like mike pointed out.

Those springs are a bit cheap and sloppily made. The threads don't match up to normal thread sizes. They mostly work, which is why there's still an antenna mount in one instead of a bolt.

I managed to hit a tree with it at about 20mph. It just laid it back and it stood easily back upright again with no damage. So it seems it does what it's supposed to.

Took some video of how they work and got one picture by accident that shows where the antenna is in the wind with a regular solid mount for reference. The first video is with no wind. The second is in Kansas at higher speed with a headwind. The photo is coincidentally along the same stretch of road as the first video, on a different day, but by the smoke there's no wind that day either.

[ame]http://www.youtube.com/watch?v=jAJtNDYrk9E[/ame]
[ame]http://www.youtube.com/watch?v=hP0KPGaCzv8[/ame]
[ame]http://www.youtube.com/watch?v=iW26aF_oyqo[/ame]

 

It's hard to find good hardware anymore. I just gave a local kid (just getting started in the CB ) a couple of springs for his dual set-up on his pick up. The springs he'd bought allowed his antennas to lean way back going down the road. The two I gave him aren't really even effected by the wind. (I hope I don't regret giving them away, probably can't replace them!!)

Kajidono, have you tried the bonding thing on that truck?

 

I'm not working there anymore so that ends the experimenting with that particular truck. I'm not sure what the bonding thing is. I really don't know that much about radios.

 

Short answer: What is lacking on these new trucks is a lack of rf ground. To help overcome that it helps to bond everything together. Use a short, braided ground strap. Ground from door to top hinge, bottom hinge to body, body to frame. Generally, the more straps the better. Keep them 18" or less in length.

 

I suspected. The studs they came with were standard and just kinda fit. That one hole was a slightly different size. That's where the sloppiness was. The springs themselves work fine.

I thought most engines were grounded with those copper straps to the frame. I'd have to find some that were coated to use on the antennas or they'd corrode and look terrible.

 

Could you cut it out with the condescending remarks? If you want to add your knowledge, more power to you, you clearly have a lot of knowledge and a lot of time on your hands to convey it, but you need to learn how to disagree with someone without belittling them.

I'm sure you're right about the 45* angle thing in theory, you know more about it than I do-but I can tell you from actually trying it in the real world that having them at 180* like described here works just fine.

Most modern trucks have pretty large braided grounding straps between the engine and the frame, which I assume is to protect the engine electronics. So they're not all that RF isolated from the rest of the frame/batteries. Essentially all trucks have air ride cabs, so usually area with the most room for improvement is between the cab and the frame because the cab is riding on rubber air bags in back and bushings in the front. There are a few trucks on the market that have cabs that are almost all plastic and fiberglass, but I think even they have some aluminum framing in them.

 

Channel Jumper said: "Using radials as a ground plane will not work on a vehicle - because the radials needs to be at a 45* angle to work properly. Anything more or less then 45* - does not work."

The 45* angle is used to raise the impedance from it's 30 ohm impedance to a 50 ohm impedance.

Any angle between 90* to 180* can be used with the understanding the input impedance will change.

Leon
(kc0iv)

 

Im soooo lost...K i have a 29ltd with an rfx75 and tested coax.....My predator 10k is mounted on a perch(on the mirror mount) and i have it grounded to the chassie with 12 ga wire..At this moment my swr is 1.3-1.5 and i keep getting told my radio sounds clear and i have talked 20mi..Dead key is 12 watts and modulated is 85watts..Heres my issue,just bought a stryker 955 and my swr is 3-3.5....
Im useing the identical set up for both radios and useing same swr meter(a seperate astatic swr/power meter)to dbl chk my swr even though my stryker has an auto cal/swr meter built in...
I opened my door and noticed my swr dropped to nothin and power on my meter doesnt go above 10 watt area.....