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SEARCHING FOR A SIGNAL, PART 2

 

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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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