Home  -  Sitemap  -  Testimonials  -  Blog     My Hotlist My Hotlist                My Account   ( Sign-in )    
4x4cb .com
UK CB Radio Specialists
Tel: 01306 881137
Browse Products My Shopping Basket / Checkout
Package DealsSpecial OffersAerialsPMR446
Articles About Us
Contact Us
DeliveryAdviceInstallingFAQsLinks
UK CB Radio Specialists - Expert Advice, Competitive Prices & knowledgeable staff, Est 1996
4 X 4 CB
Search for     in             Advanced Search
UK CB Radio Specialists - Expert Advice, Competitive Prices & knowledgeable staff, Est 1996

Installing CB Into 4x4's   Fitting the Aerial & Mount / Fitting a Roofrack / Roofbar Mount
Fitting a 2-Bolt Rack/Bar Mount   |    Fitting a Bullbar / Roll Cage Mount   |    Fitting a Dome Mount   |    Fitting a Gutter Mount   |    Fitting a Magnetic Mount   |    Fitting a PSM-1 Mount   |    Fitting a Widget Mount   |    Need a longer cable?   |   

Click to download this page as a pdf so you can print it and take it out to your vehicle to refer to when doing the job - a lot easier than trying to look at it on a mobile phone!


You are here : Installing CB Into 4x4's / Fitting the Aerial & Mount / Fitting a Roofrack / Roofbar Mount

A Two-Way Roofrack mount shown here with a 5m lead
A Two-Way Roofrack mount shown here with a 5m lead
There are two versions of this mount that we can supply in our package deals, both can be used on vertical or horizontal bars of round or square section.
Most of the photos below show the "single grooved" mount apart from the section towards the bottom of the page which shows the other type, a "double grooved" version of it, which can fit on slightly larger diameter horizontal bars. As the "double grooved" one gives this extra size yet can also be used on vertical bars, we will send this version unless you specifically say you want a single grooved one.

Installing one of our Two-Way Roofrack mounts is very easy...

What you need to do to install a Two-Way Roofrack mount :
Bolt it onto whatever bar or section you want to fit it to - making sure at least one part of the mount has a metal-to-metal connection with what it's bolted to.

(There is a way of getting an earth connection without making metal-to-metal connection at the mount - see the "Installing without metal-to-metal connection" section below)

You will need an SWR meter (a basic and easy to use test meter) to make sure you have a good earth between the mount itself and whatever you have fitted it to. If you don't have a good earth, you will have a very high SWR, and this can damage the CB, so to be sure you should check it with an SWR meter.

Most of our aerials (Springers etc) are about the right length to give a good SWR reading if all other factors are ok (some suppliers call this "Pre-SWR'd" which is rather misleading as a good SWR depends on a number of factors, not just the aerials length), but using the meter to check, and fine tune (usually by adjusting the aerials length) if necessary, as well as check that you have a good earth/ground plane, is essential.

Read our SWR meter guide.


Two-Way Roofrack/Bar Mount Physical Specs :

  • Size (of L-shaped portion) : 50mm Wide x 65mm High (excluding aerial connection)
  • Standoff from outer edge of L-shaped portion to the furthest part of the curved edge : 50mm
  • Standoff from outer edge of L-shaped portion to centre of aerial mounting hole : 35mm
  • Maximum mounting diameter : Vertical bar : 25mm ; Horizontal bar : 32mm (can be increased with our 60mm and 80mm longer bolts, see below)
  • Minimum mounting diameter : Vertical bar : 6mm ; Horizontal bar : 12mm


Two ways of fitting - Horizontal or Vertical :
This mount can be fitted on either horizontal or vertical bars - you simply undo the bolts and rotate the grooved part 90 degrees :

To change between horizontal or vertical mounting, just undo the bolts and rotate the grooved bit - it goes either way!
To change between horizontal or vertical mounting, just undo the bolts and rotate the grooved bit - it goes either way!


Metal-to-metal earth :
You don't have to go mad with an angle grinder or file, but you will need to get a clean metal-to-metal connection between some part of the mount (usually the serated edge inside the "clamp-on" bit) and your roofrack or whatever.

This metal to metal contact point only needs to be a few square millimeters, but if it is this small, make sure the the mount is not going to move over time, so it no longer touches metal (it won't move if you do the nuts up tight).

Generally speaking, the larger the groundplane is, the better the aerials performance will be - this is because the angle of radiation is lower (i.e. being transmitted along the surface, rather than straight up in the air) with a larger ground or earth.

A Two-Way roofrack mount on a galvanised roofrack - you will need to scrape the galvanised layer back to bare metal to make a good earth contact
A Two-Way Roofrack mount on a galvanised roofrack - you will need to scrape the galvanised layer back to bare metal to make a good earth contact
A Two-Way Roofrack mount on a powder coated roofrack - you will need to scrape the powder coating/paint away to get a bare metal earth contact
A Two-Way Roofrack mount on a powder coated roofrack - you will need to scrape the powder coating/paint away to get a bare metal earth contact


Installing without metal-to-metal connection :
If you cannot make a metal-to-metal connection at the mount, there are two ways you can still get this mount to work correctly for you :

If you choose to use an earth wire or earth strap to make the ground contact then the wire should be as short and thick as possible to get the best connection, and should be attached to the mount (not the aerial) - a ring terminal on one of the fixing bolts is ideal for this.

This method of obtaining an earth connection will work ok, but you will get slightly less range than if you had made the earth connection at the actual mount because the further the aerial is away from it's earth, the higher the angle of radiation will be - so you'll be sending signal up at something like 45 degrees, instead of a much lower angle, along the ground.

Using one of these methods is ideal if you have a nice new powder coated rack and don't want to scrape the paint away, or have a heavily chromed or zinc plated bar that again you don't want to scrape, or the surface of what you want to mount to is plastic coated.

A Two-Way Roofrack mount on a single roofbar that wouldn't be a large enough metal area to be a good ground - these particular bars were isolated from the main body of the vehicle so an earth wire was used to provide an earth
A Two-Way Roofrack mount on a single roofbar that wouldn't be a large enough metal area to be a good ground - these particular bars were isolated from the main body of the vehicle so an earth wire was used to provide an earth
A Two-Way Roofrack mount fitted to a single Thule type roof bar which is plastic coated and wouldn't a large enough area of metal to act as a ground for the aerial anyway - again an earth strap has been used
A Two-Way Roofrack mount fitted to a single "Thule" type roof bar which is plastic coated and wouldn't a large enough area of metal to act as a ground for the aerial anyway - so again an earth strap has been used
A Two-Way Roofrack mount on a brand new powder coated roofrack that the customer didn't want to scrape down to bare metal - here an Artificial Ground Plane has been used to provide a good earth
A Two-Way Roofrack mount on a brand new powder coated roofrack that the customer didn't want to scrape down to bare metal - here an Artificial Ground Plane has been used to provide a good earth
Another Two-Way Roofrack mount fitted to a single Thule type roof bar - this time an Artificial Ground Plane has been used to provide a good earth
Another Two-Way Roofrack mount fitted to a single Thule type roof bar - this time an Artificial Ground Plane has been used to provide a good earth


Roofrack mounting
The Two-Way Roofrack mount is ideal for roofrack bars - either round or square section and on horizontal or vertical fitting. If you are using this mount to fix to a roofrack, then you will probably find that the rack itself is a large enough piece of metal to act as a groundplane for the aerial so you won't have to worry about making a connection between the rack and the body or the battery.

If you're using it to fix to a single roof bar, you may need to use one the solutions shown above, even if the roof bar is metal because it might not be large enough on it's own to act as a ground and it may be isolated from the rest of the vehicle (this is done by manufacturers in some circumstances to reduce vibration and wind noise).

One of the factors that contribute to getting a good SWR is that the aerial shouldn't have too much metal close to it, so it's no good putting this mount on the bottom bar of a roofrack on whatever, and having the aerial right next to the top bar etc, as this won't work so well - best to put it on the top bar to start with.

A Two-Way Roofrack mount on a Land Rover Discovery's roof bar - this roof bar has a good connection with the rest of the vehicle so it was not necessary to make a fake earth of any kind
A Two-Way Roofrack mount on a Land Rover Discovery's roof bar - this roof bar has a good connection with the rest of the vehicle so it was not necessary to make a "fake" earth of any kind
A Two-Way Roofrack mount on a square section roofrack - this roofrack is a full size rack so is large enough to give the aerial a good ground, irrespective of whether the racks got metal-to-metal contact with the vehicle
A Two-Way Roofrack mount on a square section roofrack - this roofrack is a full size rack so is large enough to give the aerial a good ground, irrespective of whether the racks got metal-to-metal contact with the vehicle
A pretty standard roofrack mounting
A pretty standard roofrack mounting
A pretty standard roofrack mounting - this time vertically
A pretty standard roofrack mounting - this time vertically


Increase the size of bar you can mount on by using longer bolts :
The bolts this mount comes with are 40mm long which does limit the size of bar you can fit it to... if you have a wider bar, you might be able to use our 60mm bolts or 80mm bolts to make it fit :

Here's a Two-Way Roofrack mount on a wider bar using 80mm bolts instead of the usual 40mm ones - note also the use of an Artificial Ground Plane
Here's a Two-Way Roofrack mount on a wider bar using 80mm bolts instead of the usual 40mm ones - note also the use of an Artificial Ground Plane
Here's a Two-Way Roofrack mount on a wide roof bar using 60mm bolts instead of the usual 40mm ones
Here's a Two-Way Roofrack mount on a wide roof bar using 60mm bolts instead of the usual 40mm ones


Other things you can do to make this mount fit where you need it :
One common use for this mount is not actually as a "clamp round" mount, but as a "bolt on" mount - discarding the smaller bit and just using the right angled bracket thats left :

Here the customer just used the right angled part of the Two-Way Roofrack mount and bolted that on
Here the customer just used the right angled part of the Two-Way Roofrack mount and bolted that on
Here the customer went one further and cut the right angled bracket down to fit where he wanted it - all good!
Here the customer went one further and cut the right angled bracket down to fit where he wanted it - all good!


Other places you can use this mount
It's not just roofracks you can use this mount on...

    For example :
  • On a lamp guard on a bullbar
  • On a rear ladder
  • On any round or square bar between 6mm and 25mm in diameter
Here's a Two-Way Roofrack mount on the lampguards on a bullbar!
Here's a Two-Way Roofrack mount on the lampguards on a bullbar!
A Two-Way Roofrack mount on the mirror arm of a tractor
A Two-Way Roofrack mount on the mirror arm of a tractor
Here's a neat use for this mount - the customer fixed a metal plate coming out of the side of the vehicle, from the rear door opening and fixed the mount to that
Here's a neat use for this mount - the customer fixed a metal plate coming out of the side of the vehicle, from the rear door opening and fixed the mount to that
Here's the same installation showing what it looks like when the rear door is shut
Here's the same installation showing what it looks like when the rear door is shut

A variation on the theme, the "Double Grooved" roofrack mount :
As mentioned at the very top of this page, we do another version of the roofrack mount - on horizontal bars it can actually accomodate slightly wider bars than the standard two-way one can (up to 32mm oposed to the normal ones 25mm) but on vertical bars, you're back to the 25mm maximum diameter :

A Double Grooved Roofrack mount
A "Double Grooved" Roofrack mount
A Double Grooved Roofrack mount
A "Double Grooved" Roofrack mount

General points to remember wherever you use the Two-Way Roofrack mount :
Using this mount means you have the cable on the outside of the vehicle - it's important to secure the cable (with tiewraps) so it's not going to get tugged on by stray branches etc. Also, where there often ends up a "loop" under the mount where the plug connects - make sure you keep this as small as possible, maybe close the loop with some gaffa tape or similar, so branches etc can't snag the cable or connector.

The stud (the bit where the aerial screws in the top, and the plug goes in the bottom) has an insulator fitted which insulates the main bolt from touching the bracket as it passes through it.

This nylon insulator has a lip to it, which is designed to sit in the hole in the bar, so that the bolt that passes through it doesnt touch the bracket at all - this is important so if you take the stud apart for any reason, make sure it goes back with the lip seated properly in the hole.

IMPORTANT : This insulator needs to go at the top so it not only shields the main bolt as it goes through the bracket, but also isolates the hexnut bit at the top (where the aerial screws in) from the bracket... NOT on the underside like this :

Ooops, the insulator needs to go above the metal, not underneath it!
Ooops, the insulator needs to go above the metal, not underneath it!


Product links:
Two-Way Roofrack mount with 5m cable
Two-Way Roofrack mount without cable
Double Grooved Roofrack mount without cable
Two-Way Roofrack mount with PL/SO239 connector for SIrio Hi-Power aerials with 5m cable
4x4 CB Radio Package Deals (all of which have the option of choosing this mount)


More photos of the Two-Way Roofrack mount


You are here : Installing CB Into 4x4's / Fitting the Aerial & Mount / Fitting a Roofrack / Roofbar Mount



Search for     in             Advanced Search

PayPal Payments by PayPal

CB Radio Products  |  Search  |  Information  |  My Basket  |  Checkout

Terms & Conditions  |   My Account  |  Login  |  Contact Us  |  Sitemap  |  Home
 
Sharman Multicom Approved DealerMidland Approved Dealer
Member of the Federation Of Small BusinessesCommunication Eleven
© Copyright 2017, Communication Eleven