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SEARCHING FOR A SIGNAL, PART 2
COPY
Most competent DIYers will have little
trouble fitting a car cellphone aerial, but doing the job properly, and
ensuring optimum performance is another matter! It’s not simply a question of lining
up and sticking the bits in the right place, one of the biggest problems is
routing the cable. There are important safety considerations, so we must repeat
the earlier warning about not tackling this kind of job, unless you know what
you are doing.
We strongly recommend that anyone intending
to fit a car kit and antenna should acquaint themselves with a Department of
Trade and Industry document called ‘Code of Practice for Installation of Mobile
Radio Equipment in Land-based Vehicles’ (MPT 1362), which covers the subject in
some depth. In any case we would advise against fitting body-mount antennas,
that involve drilling holes in bodywork. There’s a lot that can go wrong, and you
only get the one chance to get it right, so leave it to the professionals, and let
them assume responsibility for any unfortunate consequences...
If you’re still with us, here’s a few common-sense
do’s and don’ts: Mag-mount antennas are clearly the easiest to fit, but take
great care with the cable entry point. If it’s going to be routed through a
door or boot-lid make sure the cable wont be crushed. If it does it can have a dire
effect on the phone’s performance, possibly stopping it from working
altogether!
Before you fit a glass mount antenna plan the
installation carefully, it’s usually a good idea to route the cable first, and
cut it neatly to length, rather than coil the surplus. Look to see where aerials
are mounted on cars of the same model as your own. Common mistakes include
mounting the antenna base in the path of a rear-screen wiper or washer jet, on
top of defroster heating elements (it will soften the adhesive), and not
cleaning the glass thoroughly beforehand. The glass must be completely free of
grease or dirt -- both sides -- otherwise it will fall off. It may help to warm
the glass slightly with a hair dryer, if you’re fitting an antenna on a really cold
day. Make sure the radiating element is vertical -- Saab owners take note, don’t
be tempted to rake the antenna, like the radio aerial!
You can take it as read that most cellphone
car antennas are intended for ‘professional’ installation. In other words the
manufacturer assumes the end-user knows what they’re doing, so they generally
have only cursory instructions.
BOX COPY 1
THE TESTS
We’ve kept our tests simple, to reflect real
world conditions. They’re in two parts, we used a static test rig and a
cellphone with a sensitive digital signal strength meter and cell site ID
display, to give us a basic set of performance figures, that will show up any
major discrepancies. The second test involves fitting the antenna to a vehicle,
taking signal strength readings and making a series of calls at fixed locations,
including areas of poor coverage. Finally
we look at the design and construction of each antenna, with particular regard
to weather-proofing, corrosion protection plus how easy it is to fit, and
remove, which you may need to do, before going through a car-wash. Most of the aerials featured here are old
friends; the fact is hardly any new models have been launched recently, apart
from upgrades and tweaks for various digital networks.
ANDREW K3
This is one of the a handful of new cellphone
antennas launched in the past year. The 3dB colinear whip is available with an open
or closed coil, the latter is designed to eliminate wind ‘whistle’ at high
speed. The mount is strong and secure with an easily lowered whip.
Straightforward fitting, and it performs very well.
Make/model Andrew K3
Type 3dB colinear whip
Performance ****
Ease of installation ***
Construction ****
WC Rating 88%
ALLGON 1128 OB 3157
A well thought-out package containing a glass
cleaning swab, adhesive, cable clips, plugs and 5 metres of cable. Very secure
belt and braces fitting (sticky pad and adhesive). Reasonably simple to fit,
good performance.
Make/model Allgon 1128 OB 3157
Type 4dB colinear whip
Performance ****
Ease of installation ****
Construction ****
WC Rating 85%
ALLGON CLIC B1138.1UK
The quick release ‘Clic’ slide fitting is an
Allgon trademark. The mounting plate contains a built in ground plane, which
helps improve performance, especially in marginal signal areas. A tough, easy
to fit design with better than average instructions.
Make/model Allgon CLIC B1138.1UK
Type 3dB colinear whip
Performance ****
Ease of installation ****
Construction ****
WC Rating 88%
CARANT GU 995
A ‘spoiler’ on the detachable whip helps eliminate
wind noise. It comes with a full fitting kit, including cable clips, cleaning
swab and Allen key removal tool. Average to good performance and a simple
fitting.
Make/model Carant GU 995
Type 3dB colinear whip
Performance ***
Ease of installation ****
Construction ****
WC Rating 80%
ORA CMS 895E
Characteristically solid design, it comes
with a generous 5 metre cable and unusually well comprehensive fitting kit
containing cleaning swabs, drying cloth, glass adhesive and cable clips. Easy
to detach and well protected mounting hardware. Good performance.
Make/model ORA CMS 895E
Type 3dB colinear whip
Performance ****
Ease of installation ****
Construction ****
WC Rating 85%
ORA CMX 720E
Uprated version of the CMS 895E featuring a
modified coupler with ground plane wings and stronger mounting bracket. The fitting
kit includes everything you need for a strong, secure installation. Improved design
give a marginal increase in performance.
Make/model ORA CMX 720E
Type 3dB colinear with ground-plane
Performance ****
Ease of installation ****
Construction ****
WC Rating 85%
ONLINE AGC3DB
A straightforward design, though the coupler is
quite bulky, compared with most of the others. Some care is needed to ensure a secure
contact. An Allen is supplied for the detachable whip. Performance ranks as average.
Make/model Online AGC3DB
Type 3dB colinear whip
Performance ***
Ease of installation ***
Construction ****
WC Rating 80%
VIVANCO AGC 1040
An elaborate design, with exposed exterior
ground planes, that could receive unwelcome attention from vandals. Whip
slightly tricky to adjust and remove. Coupler design also unusual; the 4 metre,
pre-terminated cable might pose problems on larger cars. Average performance.
Make/model Vivanco AGC 1040
Type 4dB colinear whip with ground-plane
Performance ***
Ease of installation ***
Construction ***
WC Rating 80%
WALLEN PA008
An unusual ‘Dipacitor’ design with two 120mm
(1/2 wave) radiating elements, that give improved sensitivity for both
horizontally and vertically polarised signals. Mounting bracket could do with
additional weatherproofing. Good performance.
Make/model Wallen PA008
Type Dipacitor twin whip
Performance ****
Ease of installation ****
Construction ****
WC Rating 85%
CONTACTS
Andrew Corporation, Ilex Building, Mulberry
Business Park, Fishponds Road, Wokingham RG41 2GY Telephone (01734) 776886
Allgon Antennas, 27 Manor Road, Didcot, Oxen,
OX11 7JZ Telephone (01235) 911119
Online Accessories, 1-15 Kingston Road.
Freemantle,
Southampton SO15 3DB. Telephone (01703)
237111
ORA Electronics, 28/29 Faraday Road,
Aylesbury, Bucks HP19 3RY
Telephone (01296) 415445
Vega, (Carant) Bamford Village Centre, Martlett Avenue, Rochdale OL11 5QY. Tel:
(01706) 44177
Vivanco, Unit C, ATA House, Boundary Way, Hemel Hempstead HP2 7SS. Telephone
(01442) 231616
Wallen Antennas, Les Wallen Manufacturing
Ltd., Unit 1, Trinity Place, Ramsgate, Kent CT11 7HJ. Telephone (01843) 582864
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Ó R. Maybury 1996 2711
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