CHOOSING
THE RIGHT AERIAL
Make sure you’re being heard loud and clear - The biggest
players in the communications industry help you choose
the right UHF for your needs!
Have you ever gone to call your convoy and been
told your brand new UHF is crackling? Ever
wondered why your mate’s decade old UHF is ten
times clearer than yours? Well, you could be using
the wrong aerial for your needs, and for your
vehicle. Selecting the right aerial and positioning
it correctly is a dark art that can make, or break
your ability to communicate clearly.
Ground independent aerials are the most
common types used on 4WDs. They use a
ground plane to ‘trick’ the aerial into thinking
it’s mounted to a much larger metal surface
than it is, to give a better signal. The ground
plane on this aerial is the metal piece in
between the metal spring and fi breglass whip.
There’s much more to it however, and we’ve
spoken to experts from GME, Uniden and
Oricom to get you the facts.
IS BIGGER REALLY
BETTER?
We’ve all seen those fl ashy, huge aerials bolted
to the front of big dollar trucks – no denying
they look tough, but do they really offer any
major advantages over a smaller one?
Bigger is not necessarily better. Generally
speaking, the higher dBi rating an aerial has,
the larger physical size it is. That means that a
short, 3dBi aerial is not any less effective than a
9dBi; they perform different jobs.
“There is a relationship in the antenna’s gain
to its radiating pattern. As the electrical design
of the antenna is modifi ed to increase the gain,
the omnidirectional pattern is squashed in a
vertical plane and is enhanced in a horizontal
plane. This expands the signal’s coverage. A
high gain antenna will therefore give increased
coverage on fl at terrain but the elevation will be
limited making it less suitable for mountainous
regions. A lower gain antenna is better suited
because the signal created is more of a bubble
effect and whilst the overall distance is less,
it creates more height allowing for vehicles
on inclines or on the other sides of hills and
mountains to have better performance by
getting “over” the height and being able to
reach another receiver.
GME recommends the use of antenna of
fi breglass radome construction for bull bar
mounting or extensive off-road use.”- Jim Parissis, GME
MIXING BRANDS -
HEAD UNIT AND
AERIAL
Manufacturers design their equipment to work
together with their other products, but does
matching one brand’s head-unit with another’s
aerial adversely affect your UHF’s performance?
“Our In-Car CB Mobiles are tested to work
perfectly with our Uniden Antenna Range where
there is a large assortment of mounting options
available for our antennas. Although in saying
this our CB Radios are versatile enough to work
well with other brand antennas providing the
specifi cations are compatible.”- Brad Hales, Uniden
WHICH DECIBEL
RATING?The decibel rating of a UHF aerial can dictate
specifi cally what kind of terrain your comms
setup is best suited to.
“An aerial’s performance changes accordingto its dB rating, however each has its strengths
in different environments. A low gain antenna
between 2-4 dBi is well suited for hilly terrain
but will lack range in fl at, open terrain. Medium
gain antennas in the 5-7 dBi range are a perfect
all round antenna which works well in hilly and
fl at terrain. Finally, very high gain antennas
over 8dBi are good in fl at terrain but poor in
hilly terrain. Our new range of 6.6dB Aerials
offer the best of both worlds and are perfect for
Australia’s rugged off-road conditions.”- Brad Hales, Uniden
IS IT WORTH RUNNING
TWO UHF AERIALS?
By now we understand what an aerial’s decibel
rating means and understand where each has
a place. So, does running a second, different dB
aerial connected to the same UHF radio give us
the best, or worst of both worlds?
“UHF CB radio’s generally have only one
antenna port. Whilst running two antennas
would give the users the best range coverage
over varied terrain i.e. low dB gain for hilly
country and high dB gain for fl at. The only
effective way to achieve this at present is via an
antenna switch. Unfortunately these devices are
also known to have high signal loss and in most
cases are ineffective due to this. If a user can
reduce signal loss and uses an antenna switch
it is important to ensure that the antennas are
positioned well away from each other (at least
1m) or they will have an adverse effect on each
other’s signal pattern.”- Tim Rollason, National Sales Manager, Oricom
ROOF VS BULLBAR
MOUNTING -
WHICH IS BETTER?
Logic leads us to assume that the higher up
you mount the antenna, the better and clearer
your signal will be. However, is that extra metre
really going to make a difference?
“Antenna mounting is one of the most critical
considerations in maximising performance.
Determining the best position for installation is
like thinking of an antenna as a light source at
night and how much is actually visible as this will
affect radiating patterns. An antenna needs a
large uniform metal surface beneath the radiating
elements to perform correctly. This is referred to
as a ‘ground plane’. Therefore the best position to
install an antenna is in the centre of a metal roof,
however, this is not always possible and installation
on a bull bar or mirror mount is often necessary. In
this case a ‘ground independent’ antenna should
be used to give the antenna its desired radiating
pattern without a metal ground plane. The installed
location of a ground independent antenna will play
a major role in the performance. The higher an
antenna is installed the better the performance
due to less vehicle obstructions.”- Jim Parissis, GME