Don't like the adverts?  Click here to remove them

CB radio installation... and aerial mounting

I would have thought you should have pretty good reception (assuming for the moment that everything else is correct) between Shayne in front and Clive behind but nowhere near the other way round as you would have both vehicles bodies in the line of sight between the antennae. I do get the impression from what both of you have said that your RF earth or ground planes could be drastically improved. A mag mount in the middle of the roof or thereabouts is likely to help with this. However large braided earth straps MAY help between the base of the antenna mount and vehicle body.
 
But they both work , yours better than mine perhaps because yours is mounted a bonnet length from interference whereas mine is lower than the roof line and only a few inches from it .

We could both hear Chas loud and clear and his antenna though mounted in the same place as yours is taller than his roof tent .
 
Last edited:
Clive and Shayne, you both have short aerials so I don't think you'd get the range I got even in the best of circumstances, particularly with your low mounting points.

From all that I've read, length matters :icon-biggrin: (and therefore height). Perhaps an an experienced CB user can confirm?
 
Antennas are tuned to a 1/4 wavelength (or multiple of) of the frequency they're designed to work at. At CB frequencies a 1/4 wavelength is around 2.5m. It's not so much the physical length but the electrical length that counts. Shorter antennas have loading coils in them to increase the electrical length to that required. All antennas have a 'Gain' figure in db which is a guide to their performance. The higher this figure the more efficient the antenna and the better the range. The point I'm trying to make is that a short antenna can sometimes out perform a physically longer one. Height above ground and optimum siting on the vehicle are the two most important factors after choosing your antenna. The benefit of a superior or higher gain antenna can be easily lost with poor siting.
 
I had a front bumper mounted antenna on my last 100 that worked very well but it was a long one. I would often be able to talk to people in other groups that couldn't be heard by others in my group. The efficiency of the antenna itself is probably more important than being on the roof instead of on the A/bull bar.

IMG_1619.JPG
 
I had a front bumper mounted antenna on my last 100 that worked very well but it was a long one. I would often be able to talk to people in other groups that couldn't be heard by others in my group. The efficiency of the antenna itself is probably more important than being on the roof instead of on the A/bull bar.

View attachment 110537
Er Jon, does the generous coating of mud have a detrimental effect on the aerials performance? :think:
 
Don't like the adverts?  Click here to remove them
maybe in theory Chas, especially when wet, but I doubt it would be a significant percentage performance loss :)
 
I had a front bumper mounted antenna on my last 100 that worked very well but it was a long one. I would often be able to talk to people in other groups that couldn't be heard by others in my group. The efficiency of the antenna itself is probably more important than being on the roof instead of on the A/bull bar.

View attachment 110537

So size does matter then Jon, maybe mine is too short, or at least I might be better off with a longer one?
 
So size does matter then Jon, maybe mine is too short, or at least I might be better off with a longer one?

That fat bit at the bottom of your antenna likely has another 3ft of wire in it so size is not necessarily the problem . I remember reading somewhere that you should set up in a good clear area which tells me they are prone to interference .

Both Jon and Chas have an antenna taller than their trucks and with the 6 cylinder bonnet being about 4 miles long ...........

I think i will just mount mine on the roof and be done with it , pita i lost the key so i can't fold it down for a drive through car wash though :doh:
 
Thanks Dave its an idea , i could make up a key i suppose its only a flat round bolt head with a couple of small holes and the key went unnoticed on my car key ring .
 
The wire coil at the base is a matching coil to give the antenna the correct impedance to compensate for it being shorter than the ideal and does not transmit the signal so you still have a short less efficient antenna even if there seems to be a lot of wire in the base coil.

Size does matter Clive but even a big antenna will be rubbish without a good ground plane and your bonnet may not be providing a good ground plane at the moment.
 
The wire coil at the base is a matching coil to give the antenna the correct impedance to compensate for it being shorter than the ideal and does not transmit the signal so you still have a short less efficient antenna even if there seems to be a lot of wire in the base coil.

Size does matter Clive but even a big antenna will be rubbish without a good ground plane and your bonnet may not be providing a good ground plane at the moment.

Yes Jon, actually the "ground plane" bit is just about the only part of this that I've grasped to any extent :lol:.

I'm going to try a braid from body to bonnet and see if I can source a longer antenna locally. It will be a start.
 
As was predicted, my gutter mount snapped on my second laning trip :(

Has anyone tried one of the heavy duty stainless steel gutter mounts? Or a Sirio branded cast mount (which are sold as being 'stronger')? The cheapo gutter mount really was useless. It felt flimsy and when it broke the casting just snapped in half.

I've seen people mount them on the offside C-pillar, next to the door but the pillar on mine is a box so I would have to make a big hole in the inner skin to reach the inside of the outer bodywork. If Bert sees this (or anyone else who's done it), did you find the same?
 
As was predicted, my gutter mount snapped on my second laning trip :(

Has anyone tried one of the heavy duty stainless steel gutter mounts? Or a Sirio branded cast mount (which are sold as being 'stronger')? The cheapo gutter mount really was useless. It felt flimsy and when it broke the casting just snapped in half.

I've seen people mount them on the offside C-pillar, next to the door but the pillar on mine is a box so I would have to make a big hole in the inner skin to reach the inside of the outer bodywork. If Bert sees this (or anyone else who's done it), did you find the same?

I had to make a big hole in mine to get to the outer skin..... but like you, I'm still not certain it would stand up to a BIG knock or snag..
Capture.JPG
 
Oh! I've seen that photo before, but I didn't quite realise what I was looking at. So that's looking through an oval hole (with grommet) on the inner skin of the C pillar and seeing the base plate of the mount on the back of the outer skin. Cheers Bert

It's a far more sheltered placement than the gutter, and it looks neater too. I'd previously though about drilling the roof, but if it got ripped off by trees it'd leave a nasty gash in the roof.

The only disadvantage I can see is that the aerial will make a racket banging on the bodywork when it catches in trees and starts twanging. Maybe it could be made more upright by fitting a directional adaptor?
 
Oh! I've seen that photo before, but I didn't quite realise what I was looking at. So that's looking through an oval hole (with grommet) on the inner skin of the C pillar and seeing the base plate of the mount on the back of the outer skin. Cheers Bert

It's a far more sheltered placement than the gutter, and it looks neater too. I'd previously though about drilling the roof, but if it got ripped off by trees it'd leave a nasty gash in the roof.

The only disadvantage I can see is that the aerial will make a racket banging on the bodywork when it catches in trees and starts twanging. Maybe it could be made more upright by fitting a directional adaptor?

Hi Dave. So far I've not had any banging going on. The part under the coil is solid so the only movement is the aerial above the coil. It moves about a bit off road, but to date, not hit the body work.
 
I have wondered myself about welding a fold of metal on the roof at the rear , bit like a shark fin so the grommet itself doesn't even get wet . It's a scary thought but hey i'm never gonna sell the truck so if it works for me why not .
 
New mount fitted! Not tested yet, but it can only be better than the cruddy gutter mount. I used my existing co-ax cable. I trimmed back the insulation and added a couple of standard ring terminals that I crimped into place. The aerial (I've got a standard length springer, which is quite long) points forward and towards the centre of the car at a crazy angle. I quite like it :) but I could correct it with a directional adaptor.

b.jpg
a.jpg
 
I think there's a case for having a sacrificial mount if you're offroading/greenlaning and have a fancy antenna. When I was in Scotland last year I came across a guy who had just snapped off his on a low branch and buggered the motorised loading coil in the base. No big deal you might think but it was £350's worth!
 
Back
Top