Can anyone reccomend one that works!!
I have tried a few and none seem to work well and some do not work at all.
Paul
Digital signal can be funny, on my S7000 it can work in one place then move it a couple inchs and it loses signal. Can very much depend on where you are in relation to the transmitter.
The aerial I have came with the S7000 and its only 5-6 inches long stalk. Works a treat in good signal areas
Beetie is on the right lines according to this link (Its a compact “log-periodic”)
aerialsandtv.com/touringaerials.html
Some gain, wide band, attenuation (reduction) of signal from other directions, easy stowing when not in use.
I have a status mounted on back of cab 99% of the time it is ok and you can get a signal, but as Alcapone said it can be hit and miss, I was told that in some areas the digi siganl is not running at fulll power until after the switch over as it knocks the old analogue signal out so that could explain the lack of signal sometimes.
Also I found mobile phones seems to knock the signal out, I find if I put them away from the tv it’s ok that is until the tracker mounted in the dash decides to conect to the system 
.
Phil in the cb shop at Gordano services has some digi aerials that seem to work well
I got 1 from B+M’s, £15 quid, works well most places and where it doesn’t, if I plug it into the mains (inverter) then it seems to work.
I’ve only been on 1 job in last 4mths where it had no signal, and to be honest, I couldn’t pick radio 2 up on the truck stereo either, so didn’t expect there to be one.
What you want is an ariel made for digital.
So get yourself to either a caravan store(these antennas can be good because they can be taken apart easy) or just get yourself a normal digital TV antenna and you will be away.
Some of those caravan ones are pretty crap to be honest, they will say they can be used for digital, but without the digital tick, they arent a proper digital TV ariel.
Some will say they are compatable, and they will work on digital, but it doesnt mean they will work any good.
Thanks Gents, I will have a look about.
Paul
Somethings to bear in mind, Paul. The omni- directional (look a bit like a mushroom) aerials that are often seen on caravans have NEGATIVE gain and the pre-amp (booster) will only boost the signal so if you have a weak and noisy signal at the aerial, the booster will give you a strong and noisy signal. The ONLY way to improve the signal quality is at the aerial.
The laws of physics say that you cannot have something for nothing so an aerial for poor reception areas will have higher gain but will need you to take care with lining up the aerial (The aerial is sharper).
At my home we can receive pictures from Waltham and Belmont but one problem is Belmont’s analogue is on Waltham’s digital so another reason to have a directional aerial.