As I’ve mentioned before, your choice of aerial is will play a big, if not bigger role in how clear and how functional you’re UHF CB is.
They come in so many shapes and sizes and it can get very technical so I’m going to try and explain as best I can. Hopefuly it will help you make the right choice.
The working parts of a UHF aerial.
Height:
The height of your aerial or antenna will typcialy reflect on it’s performance. Taller is better from a pure communcations pespective, but if it’s not removable it can be a real pain with general driving (I’ve taken out a few lights in undeground carparks). When you talk about height though, it’s also about location as well as length. The ideal location of the aerial is actually on the middle of your 4×4 on the roof. We put them on bull bars for ease of management and to make sure that heavy peice on steel slowing our 4×4 down is good for something.
Thinkness:
You’ll see various thinknesses and that’s typically related to gain (mentioned below) or the owener compensating for something. I’ll leave that to your imagination.
Base:
This is how it mounts to your rig. There will be base fitting to secure the coax cable to the aerial. There’s a lot of difference shapes and sizes. You can also have atteched to the base is a ‘whip’, that allows for movement of the aerial. Good if your running around in tree lined tracks and are using a more solid arial.
Flexibility:
The ‘whip’ base mentioned below will give you some flexibility. These are almost essential if you are running a super thick broomstick style. If you are running a thinner fiberglast or even metal arial, it will have felxibility enough to pehaps avoice having to use a whip.
Gain:
Okay so this is where it all happens with regards to the type of antenna you need. Gain is measured in ‘dBi’. Now, biggest is not always better. The rule here is the bigger the gain, the longer distance you will get, but the narrower the beam.
This if it like pencil beam headlights v’s wide. Pencil cast light longer, but not as wide. The same goes for dBi. Lower dBi means wider but less travel (3 to 5). Higher (6-9+) means longer travel less width.
So…
- Higher dBI: awesome performance on flat terrain
- Lower dBI: awresome performance on hill terrain
- Middle dBI: great all rounder
What performance to expect:
The distance you get out of your UHF aerials is going to be subject to the gain, the hight, and terrain and even the climate. It can be as short as a 1km to 20km. Using repeaters as discussed in our Channel list can massively extend that range (to over 100Km).
Cable lengths:
For a long time I was led to believe the length of your cable mattered — the truth is it doesn’t for UHF. You should try to keep it as short as possible and use a good quality coax cable to reduce signal loss, but it’s not going to have the imact I thought it did. Another old 4x4ers tale.
Multi aerials installations:
Given you might be wanting to head to the flat outback one day and a high gain aerial is best, then the next to the high country and a lower gain is better a dual aerial installation might be on the cards. And there are a couple of options:
- 2 aerials, 2 UHF CBs: you can run two independant setups to to CBs but you need to be careful with distancing as they may interfere with each other
- 2 aerials, 1 UHF CB with coax cable joined: I really wouldn’t bother with this as its very fiddley. They two coax cables need to be exactly the same length and they might still interfere with each other… a nightmare and stay away.
- 2 aerials, 1 UHF CB, coax cable switched: This is the setup I run. I have a switch in cab that will use one aerial or another. It is easy to setup and works perfectly. Giving you quick access to the right aerial for the job.
So for a quick check:
- What sort of gain do I need for my application
- What is the maximum height I can get away with
- What fitting / felxibility do I need in the mount and aerial
- What’s my budget
If you think about these for things, you’re going to be good shape!
Switch…
Hi there mate, i have a 60 dBi on bullbar, a 2.6dbi on top of my 4×4 on the right side and a 9.6dbi flexible foldaway wip on top of my 4wd on the left running to a 3 way switch to one radio.
My question here please. Is it ok to use the conventional type of connection to all 4 points? I mean the three coming from 3 and antennas and the one going out of the switch to the main unit or should I cut those three cables I mean the three in and the one out and actually sold them inside the switch unit thank you
In this case with three, I’d be doing a three-way switch. Connections are connections as long as you can only have one ‘active’, you don’t have to worry about distancing.
Thanks mate. The system works a treat now. Three antennas connected to the switch the one cable going to the main unit.. Thanks
Thanks for the read now I have more understanding of uhf aerials
hey there, i have a i-com unit and was wondering if you can only use the antenna that comes with it or can you change out the antenna for anything else.
Shayne I think you should do a bit of a spellcheck before publishing an article mate. This is shocking.