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The Hype behind the tall.
Buy a really big aerial and you should be able to speak and listen far beyond what your mates can.
Read a CB or 4 x 4 mag and they'll rave about the 2.75 m tank whip aerial.
A God amongst mobile aerials this thing is 9 feet of steel.
Of course you'll smack anything you drive under so they all make sure it's mounted on a VERY large powerful spring.
Take an average Defender 6'5-8". Add 9' of whip and 6" of spring (recommended) 16' 6" (ish) and that's assuming some devoted mud plugger hasn't jacked up the suspension.
But is it any good?
Yes (ish)
Firstly we'll look at mounting the beast.
Where to put it?
It needs metal beneath it. Lots and lots of metal so it needs to sit centre mass right in the middle of your roof.
Forget about the rear bumper, gutter, and front wing (unless there are two of them 9 feet apart).
Older landy's had aerial tuning units on the wings, unless you've got that, your choices are VERY limited.
These whips have no loading coil so to be effective they need to 'see' 360 degrees round the vehicle.
Aluminium or thin metal roof? Don't even think of going there.
One decent clout at speed and your roof will take on a whole new shape. On a Landy you'll probably need to mount a BIG sheet of metal to stick it too.
Does it like mag mounts?
There isn't a simple answer here. The whip is a full quarter wave aerial. It needs 9 feet of metal beneath it. I drive a van. No problem. 2-4 door hatch back. Errrrr, it might work.
Smart Car, No. (Don't laugh, I have been asked).
Does a mag mount work at all ?
Yes BUT it needs to be big. I mean SERIOUSLY BIG.
It has to 'project' or kid the aerial that it is on one seriously large ground plane. Add 6" of spring (recommended) to act as a shock absorber and you may have problems.
As there is no electrical contact between the coax and the roof, a lot of power gets wasted INSIDE the cab as the coax will be radiating power because of this.
In short, you're sitting in a low frequency microwave oven!
It also weighs a lot especially when driving and it's getting slammed by the wind.
I don't often say this but even a 3 magnet mount might struggle on a motorway.
Does it perform better on a hole mount?
Ummmmm ditto I'm afraid. I'll perform better than on a mag mount BUT small cars remain a serious problem.
OK, Stuff it, I'll use it as a base aerial.
Ohhhh Errr. It 's still looking for 9 feet of metal.
You'll need to put out some 9 feet radials for it to work and raise it off the ground another 9 feet.
Good news, you don't need the spring!
So to recap mounting.
It's looking for 9 feet of ground plane.
Seriously large mag mount needed, preferably a hole mount.
Gutter and boot lips mounts, don't make me laugh.
The mag mount or hole mount needs to be in the centre of the vehicle.
It needs protecting so fit a spring. The spring WILL affect the tuning and the aerial will appear WAY TOO LONG!
Tuning the beast.
I have to say that tuning in most aerials is a bit of a black art. Two identical installations will tune differently.
I love the way some manufacturers mark on the whip CEPT and UK to allow you to set the aerial "perfectly".
Rubbish.
Every aerial needs tuning and these big boys are the worse to get perfectly right.
I've tuned them in only to find that adding a passenger throws the tuning WAY OFF. Add a bit of rain, and a wet vehicle changes it's electrical appearance so your ground plane changes ergo, the aerial appears mis-matched.
Firstly if you have a UK only rig, it's going to be too long especially if you've sensibly added a shock spring.
Ideally if needs to be 2.68-2.72 meters for the UK Frequencies and for the CEPT (EU) frequencies it needs to be 2.74 to 2.78 meters.
That’s an incredible 4 inches difference (10 cm) or 25 cm if you add a 6 inch (15 cm) spring.
Those of us who have tuned shorter whips will have found that you are usually working in millimetres when tuning the SWR down so just how does this big boy behave?
Single band UK figures can be good with < 1.3:1 across 40 channels.
Then you add another 40 channels, CEPT. about the same BUT it will favour the middle channels i.e. CEPT Ch. 20 to UK Ch. 20.
Should you use an aerial tuning unit?
I'd say yes especially if you want to use power. However some installations SWR in to < 1.1:1 i.e. almost perfect.
An ATU in a cab? Mostly you're just adding to your low frequency microwave effect.
Conclusions:-
Stick with a conventional sized whip for mobiles.
They won't damage a vehicle bodywork, hopefully anything it hits, and it a lot more friendly to tune and operate through.
Use a long antenna by all means but stop, park, and then swap the little one for your big stick.
If you insist on using a big aerial, consider adding a choke balun to it OUTSIDE the car, right alongside the aerial.
Do I own one?
Yes but mine is carried disassembled in the boot and set up where I want to operate.
Does it make a difference?
I can hear more on bad days BUT I've also talked to South Africa on a 4 foot whip before now.
You're call.
Basic Rules for all aerials:
Taller Aerials perform better than shorter ones.
Aerials that are mounted higher perform better than if mounted lower.
Single Aerials perform better when mounted as close to centre as possible on metal vehicles.
Fibreglass vehicles, or those with little available ground plane, need co-phased or "no ground plane" Aerials.
The physical length of the aerial is all about the law, how much you want to hit things, and the strength of the aerial mount and roof itself.
At least two-thirds of the aerial should be above the vehicles roof line for optimum performance.
The bandwidth of the aerial should exceed the needs of your rig.
On a CEPT / UK CB that’s just over 1 MHZ. Look for an aerial that can tune over 26 to 30 Mhz.
If you put 4 watts into a 102-inch whip, it is the same output as if you put 11 watts into a 3-foot whip.
If you put 4 watts into a 102-inch whip, it is the same as if you put 14 watts into a 28-inch antenna.
If you put 4 watts into a 102-inch whip, it is the same as if you put 54 watts into a 7.5 antenna.
If the SWR on channel 40 is greater than that on channel 1, your antenna is considered to be "LONG" and reduction of physical height and/or conductor length will correct this situation.
Add a spring and the aerial will appear too long by as little as the length of the coil (if tightly packed) or the total length of the spring if unwound. A wildly unpredictable amount.
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