UHF, Aerials and Reception
John Westbury talks UHF, explains DBGAIN and tests out two Aerials
Some many years ago when my hair was much darker and I had more of it many people
used the old AM CB radio and at that time you had to pay to have a licence and operate. Many aspects of communication have changed over the years and today the old CB is gone and we are blessed with the UHF system which offers a much better range and audio quality.
Trucks, Convoys and Parking
The UHF radio is really a must for travellers these days, and, it is estimated that 85 percent of those towing caravans use them for various reasons. Some vans have stickers on the back indicating they use both UHF Channels 40 & 18. Channel 40 is used by trucks who, more often than not when they see it, will call a caravan to let them know they are going to pass. Often, when I see one behind me I call them and let them know I can see them and invite them to pass when they want to. Always, after they have passed, they flick their indicators left and right as a message of thanks.
I always suggest to fellow caravanners that they wait until they are out of city limits to use Channel 40 as sometimes there is the odd bit of language on it. On the other side, UHF 40 is handy in that if your van is having a problem, trucks and others who use it can alert you to it before anything untoward happens. There are also caravan convoys who use Channel 18, and some travellers, who don’t have cameras on their vans, use them for parking instructions.
Cattle Stations and Repeater Stations
Another interesting factor with UHF is that if you suddenly do
not have mobile phone reception you may well find your UHF radio will operate via various repeater stations situated around most parts of Australia. I was in the outback some years ago when I picked up a call from a caravanner on UHF 40 who was in a bit of trouble and he did not have any mobile phone reception. Luckily, we were headed his way and was able to help him get back on the road.
You will also find that nearly every outback cattle station operates UHF radio and most have a sign on their main gate indicating the channel they use, and, this is very helpful if you need any advice on roads or other matters.
Antennas, why they matter?
There are various brands of UHF radios available, and it is tour choice what you use, but, at the end of the day the antenna you use is vital to your UHF radio system. Even the best UHF radio will perform poorly if it is connected to a cheap antenna. A good quality antenna will improve the distance and clarity of your transmissions, and, will also have the same effect on receiving transmissions.
What is dB GAIN?
Antennas are generally rated in what is known as “dB gain”. It is a common misconception that the higher the antenna gain the greater the transmission distance. While this is true to some degree, a higher gain 9dB antenna will have a very narrow or directional transmission field making it ideal in open country but not so good in mountainous areas. A low gain 3dB antenna won’t transmit as far but it may perform much better in hilly terrain.
The Quick-Fit Fix?
You can purchase antennas that have two aerials on quick-fit connections, allowing you to
swap aerials between hilly and flat terrain. From my experience, most of the Australian continent is pretty flat. Mountainous terrain is more the exception than the rule. For this reason, I suggest fitting an antenna with around 6dB gain as this is a good compromise.
Our Aerial Test
So, is there a difference with UHF aerials? I road tested two aerials which were just put out by Uniden Australia and the results were quite significant.
Aerial one (our control) is an ordinary slim line and while reception/transmission was average, distance was about one kilometre.
Uniden AWX970S
Aerial number two is the new Uniden AWX970S. With the assistance of Stephen Brown of Toffolon Motors at Seaford in Melbourne we replaced aerial number one with this one. It has a whip length of 570mm. Reception/ transmission was much better and a distance of up to 6-kilometres was achieved.
Uniden ATX970
Aerial number three is the new Uniden ATX970. It has a whip length of 1068 mm and a mounted height of 1200 mm. Reception/ transmission with this aerial
could only be described as unbelievable. I reached a distance of 15-kilometres with no static or interference, and the receiver I spoke with could not believe I was that far away.
However, as Stephen also points out, transmission/reception can also vary on what is known as “line of sight”. In both test cases I changed my line of sight with the same results. Both results can only thus be described as fantastic and there is no doubt Uniden Australia have done some good homework on their new aerials.
