Yup most are 12v and most caravan aerial amplifiers are inside the caravan.
Perhaps a bit of explanation is in order why I asked for suggestions regarding 5v and antenna with the gain block near to the dipole element:
I've been a radio ham (GW0MOQ class A)since the early 1990s and it's hard to get away from good practice that is.. every amplifier amplifies every thing it sees on its input. So any 'noise' which enters the cabling between the resonant dipole and the amplifier input is amplified in addition to the wanted signal. Which generally is not a good thing.
I mentioned the claimed Hama gain of 18db.... is that dbi or dbd?.... a retailer can get away with vague a specifiation much in the same way that audio amplifiers output can be expressed as music power, RMS or peak.
I hope that this explains why I am looking for suggestions for roof mounted (to benefit from the vans metal roof / ground plane. ), 5v because that's what the TV provides, and the reason why I want the amplifier at the antenna.
Yagi are directional and polarised so require pointing. Omnidirectional don't but admittedly have less gain, which makes the amplifier class and location important.
If anyone has a suggestion for others like the ebay Hama ones I really would love to check them out.
Nick