UHF Antennas Everything You Need to Know

Whether you are trekking through the outback or through the bush your choice of UHF antenna can determine if your transmissions come through loud and clear while still being functional.

It can be rather confusing when getting down to the nitty gritty things – I know I had a lot of trouble when I first went looking for an appropriate UHF antenna for my own needs. Hopefully, from all the things I have learned I can help you out and make your antenna choice that much easier!

First off, UHF antennas allow you to communicate and connect with others on a single frequency of 477MHZ. This could be in a group, convoy, in an emergency situation or just to see who is out and about. They transmit best by a line of sight, this doesn’t necessarily mean what you can see but what the apex of your antenna can see.

Often when it comes down to the final decision it is based more around how practical, how function and what features you really need.

Why the Antenna is Important?

Essentially, your antenna is the eyes and ears of your radio. You need it to see incoming signals and hear the the incoming transmissions clearly. If you mount your antenna poorly or it is of poor quality it can reduce how effective and reliable it actually is. Purchasing a quality antenna that fits your requirements is the best way to ensure that you have reliable and effective communication while exploring. Always remember to test your radio before you head out as it may just save you!

UHF Antenna Basics

When it comes to your antenna there are a few things you need to be aware of. These can change how effective it is and how functional it is for your needs.

Height

When it comes to the length of your antenna, the height it reaches will typically reflect it’s ability to perform. However, you may not need the tallest one – from a communication perspective a taller one is better but you need to make sure your antenna is functional for you in all occasions.

If you have an extensively long antenna and you don’t have the option of removing it – it will become a nuisance, Especially if you are in an underground car park – you may take out a light or two!

Location

Where you mount your aerial can affect the signal it is able to pick up and transmit to. The ideal location is actually in the middle of your roof! But this isn’t always the easiest to get to or mount. Often they are mounted on the front guard or the bull bar. This is the easiest location for decent signal that still allows you easy access to it When you do this it is essential that you use a ground independent antenna and mount the antenna away from vertical metal section ie windscreen pillars, other antennas etc. Vehicle metal structure can shadow your transmission making them quite, hazy or even disrupted by static.

You should also mount the antenna as high as possible. The higher your antenna is the further it will be able to ‘see’. This gives you a further distance of communicating which could be vital in a emergency situation. Even the most simplest of issues can become a dyer situation when you are away from others.

Base

The base is how the antenna is attached to your motor vehicle and how the coax cable is secured to your aerial. You want to ensure it is secure and picking the right base is essential. Varying in sizes, shapes and materials makes sure that there is something for everyone’s rig.

Attaching a whip to the base is also advised, especially when your antenna is rather ridged. A whip enables movement which is particularly useful if you are trekking through bush that will continuously be connecting with your aerial.

Flexibility

Depending on the material that your antenna is made of will determine how much flexibility it has. You can run into issues if you don’t use a whip and your antenna is extremely stiff. If your chosen antenna is quite flexible you may be able to forgo a whip altogether – you just need it to suit your use. If you need it to be able to bend it to get it into a carport or bounce back after being pulled in tree branches you may opt for a whip and an antenna that is already flexible.

Cable Lengths

When it comes to cable lengths, it doesn’t actually matter (unless you are running a multi-antenna system – discussed further down) – the quality is what really matters. A cheap cruddy cable is not going to last you very long and it may even prevent you from clear transmissions. Do your best to keep the cable as short as possible and use a quality coax cable to reduce any signal loss or noise in transmissions. You may have to invest in a more expensive one but trust me it is going to be worthwhile.

Gain

This is probably the most important aspect of a UHF antenna. Gain is measured in decibels (dB). If you are trekking through the hilly countryside or scouting across the vast outback it is going to determine what gain you need.

Low Gain

This is around the 3-5dB range and is best suited for hilly terrain. You need to picture the signal as an apple, it is wide but short in distance. This is great for hills as it give you the height and depth required for communication at different levels of elevation.

High Gain

This is around the 7-9+ dB’s. This is best used for terrain that is flat. The signal is more of a flat platter shape – it is long in distance but shallow in depth. Amazing for adventures in the vast outback as it goes for long ranges. High gain doesn’t give you any height or depth for different elevated altitudes, straight line of sight from the apex of your antenna.

Climate/Conditions

Although this isn’t something your can necessarily control you need to be aware about it. Your climate and the conditions you are traveling through can also affect the signal of your transmissions. If there is a lot of dust, cloud or electricity in the air it can cause interference as the signal tries to pass through it.

Which antenna is best for me?

Your choice really comes down to what you need it for. You should ask yourself these questions to assist in deciding what is going to be the best option for your needs.

  • Are you going to be trekking through hilly terrain? Low gain antenna – Hilly Terrain round 3-5dB
  • Do you frequently venture into the outback? High gain antenna – Flat terrain around 7-9+ dB
  • Do you alternate your adventures from one to the other?

Moderate gain antenna – Great all rounder for a combination of hilly and flat terrain. Around 5-7dB. Otherwise you can opt for both a low gain and high gain antenna to accommodate any terrain and ensure you have the required range you need. This brings us to our next point.

If you are in a convoy or a group where you are only going to be communicating with vehicles roughly 1km in front or behind you a short rubberised antenna, around 150-300mm should suffice. It is recommended to ensure at least one or two people in your group have a set up that can reach further distances in case of an emergency.

If you are looking to communicate with those further than 1km radius you are more than likely going to want to invest in a fiberglass or aluminum antenna as they are a little sturdier than a rubberised one. The length you need could be as little as 1m to one that is over 2m. This really depends on the gain your antenna provides as well as what is functional for you.

What Are Multi-antenna Systems?

This is probably the best option if you know you are going to be exploring the outback to the hills and god only knows where else! There are a few options when installing a system with two antennas.

2 Antennas, 1 UHF CB radio with the coax cable joined

This is most definitely a more complicated option to install. It is advised that you avoid it unless you like a fiddly-diddly-do situation. This requires your two coax cables to be the exact same length and I mean exact, otherwise you are going to end up with interference. You also need to make sure they are a sufficient distance apart otherwise they will interfere with each others signals preventing you from getting the full advantage of them both. This set up can just be a nightmare.

2 aerials, 2 UHF CB radios

This is functional and useful – however it can be a nuisance as you have two independent set ups. You must be careful with the distance between the antennas, otherwise they will interfere with each other and render them pretty much pointless! Not to mention the extra time of assembling and securing your setups.

2 aerials, 1 UHF radio and a coax cable switch

This is probably the most functional and effective of setups. You install a switch in the cab which allows you to switch between antennas. As you have a switch the antennas don’t interfere with each other as technically one is off while the other is on. It is also quick and easy access to both of your options whenever you require them and it is rather easy to install it. With this set up you can run more than 2 antennas if you really want – however if you make the right decision when purchasing you will only need 2 to cover all your requirements.

What is a ground independent antenna?

A ground independent antenna can be extremely useful especially when mounting on a bull bar, uneven surface or even on one side of your vehicle. Ground independent means that it simulates a ground plane to ensures it performs correctly even if there is minimal to no ground plane. A ground plane is the surface your antenna is affixed to.

An independent ground antenna can also help to correct the signal range of your antenna. If you fix your antenna to one side of your vehicle it can create a lop sided signal. By utilizing a ground independent antenna it corrects the signal slightly to ensure it is a little more even. It also corrects the signal if you mount your antenna on an uneven/sloping surface.

What Are Antenna Mounts?

When it comes to fixing your antenna to your vehicle you need to be sure that it is reliable and secured well – we can all put our vehicles through some intense conditions! Depending on the mount you get will determine where you after able to secure it. Here are a few options:

  • Magnetic based – usually a powerful magnet combined with a intense suction cup to ensure your antenna stays mounted. Remember it is a magnet so it will only attach to a metal surface.
  • Remove-able mount – gives you the option to remove your antenna from your vehicle. This is a great option for someone who only need a temporary setup every now and then when you get the time to go out exploring.
  • On glass mount – allows you to attach to glass and usually only a temporary set up for that weekend away.
  • Brackets – these are usually made of stainless steel to ensure a study material. There is a wide range of bracket to suit vehicles and location if you want it mounted to the bonnet, your bull bars, your boot etc.

Having an idea of where you are going to be attaching your antenna can save you money prior to buying your mount.

Hints and Tips

Don’t coil your excess coax cable as it can create problems. This causes the cable to become an conductor – this can produce a voltage spike down the cable and back into the transmitter and blow up the output stage transistors, it can also cause noise when sending and receiving transmissions. The solution to avoiding this is to shorten the cable at one end to the desired length. This won’t damage the antenna or signal regardless of the dB. If you don’t want to shorten the cable or you aren’t able to, the next best option is to run it in long loops under the dash to assist in avoiding the creation of the above issues.

Remember your antenna will be the most effective the closer it is to vertical. If your antenna is flexible it may lose a little performance as you drive due to it bending, however it should be find when you are stationary. If you have your antenna tilted and not completely vertical you change the distance and area for signal. Picture tilting a flat platter dish – some of the platter is in the air, while the other end is sloping towards the ground which isn’t really useful to you.

If you are going to be traveling down corrugated roads often they have a tendency to shake aerials creating a weak point and snapping clean off -this is in particular of steel antennas. To avoid this you could wrap some self-vulcanising tape around the base and a partial way up the antenna – say around 1/3 of the antennas length. This limits your whip affect, minimising the possibility of snapping off due to the weak point that is now avoided.

When it comes down to it you need to make sure your antenna comes with warranty and good customer support. Nothing is always perfect in the world and in case your purchase is faulty, has an issue or something out of the blue happens you can take advantage of the warranty.

Remember to read the fine print and ask what the warranty covers. Some manufacturers may have specifications on where and where not is acceptable to mount your antenna making the warranty void.

Don’t forget to check all the boxes to be sure you purchase the right antenna!

  • What is the maximum height you can get away with without causing function issues?
  • What gain do you require for your needs.
  • What fitting or flexibility do I need in the mount and aerial?
  • What can I spend?

Related Questions

Are there antennas available in between 3dB and 4dB etc?

Yes! You don’t just have to stick to whole number dB’s they come in a range to ensure everyone can get what they require. You are able to purchase 3.5, 7.6, 5.6, 4.2 etc throughout the dB range.

What brands should I look at?

When it comes to brands there are a few major players that are reliable, worth the investment and they also have great customer support and product warranties in case something does go

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