Shark fin type radio aerial

[SilverSurfer]

Hello again, been trying to sort out a radio aerial for my caravan and have had a few suggestions. Just seen a shark fin aerial on eBay and was wondering if these are ok for caravans. Do they need to be earthed to metal, better on roof or side wall? Do they give good reception?
Please help

 

[Sproket]

I thought the shark fin aerials were meant for GPS reception, just like on the BMW's for their sat-nav units.
But I have found this

These fins are only really suitable for GPS and Phone frequencies hence their short length. Radio reception requires something longer.

When we have the radio on in the van, it comes though the telly via the satellite dish & sky, but I have a small portable dab radio from asda for when we are packing things away.

 

[WatsonJohnG]

I replaced the stick aerial on the Kuga with a Sharksfin and it is fine on AM and FM
You have to be sure that its an aerial and not a look alike
Usually it states for appearance only if its a styling accessory
There are a couple of types
Usually you unbolt the old car aerial which involves taking the headlining down on the Kuga but I got one that has a small printed circuit and it just attaches to the old aerial base