Portable digital TV roof aerial, any good?

If you mean VisionPlus, yes, they are good. Again, rotatable uni directional is better than fixed omni directional. 

https://visionplus.co.uk

A tad better, I suggest that free standing SAT dish ‘cos at least that free standing one gives some positional advantage over the roof mounted ones. Mine has a 25m metre cable, in fact the same one I use for the bollards. That gives me a possible 25m radius of possible line of site from the van. The rest is choosing that right pitch! Sometimes, just sometimes my aerial works mind!😁

I haven't set up my sat system for ages, I checked the HD receiver still works so its just getting the dish right! I have downloaded a sat finder app, so hopefully I'm halfway there I used this system in Holland but for the love of me I can't remember how we set it up. I'm sure it will come back to me.  I was hoping g for an easy option

Well my husband said we'll buy one and see,so we went to a little cl for the weekend and tried the antenna, it was amazing, I stuck it on the roof of my car and put the lead through a window, plugged it into TV,  located plug and play on my TV and tuned it in. Was fantastic picture, at night I said to my husband to bring the aerial in and it worked inside. I was so impressed. I know it may not be as good on other sites but for £25 I'm well impressed 

do you have the post code for the CL  site as it would interesting to see how far away the transmitter was

Just don't park under a tree and find it is blocking direct line of sight to the satellite.

Yes, they do work in particularly strong signal areas giving a false impression that they may be effective everywhere. However, many will struggle where this is not the case. Unfortunately in the countryside areas we visit they have less than desirable signals broadcast to them so I have my portable SAT system with me just in case. 

As pointed out VHF & UHF signals are line of sight and as you are aware pass through the atmosphere hence you get satellite tv and Nasa can contact their space crafts, lower frequencies  bounce of the  ionosphere (skip) remember listening to radio Luxemburg on the MW were the signal would fade in and out due to  atmospheric conditions. 

 As pointed out VHF & UHF signals are line of sight 

They work better if there is line of sight but you can receive some signal even when they are not. The lower the frequency the better the chances.

Where I live, I have no line of sight to the main TV transmitter but with the right equipment, hi gain aerial and a low noise mast head pre amp I can get an excellent signal.

peedee

It’s not just distance that influences the reception, topology of land, how powerful the transmitter is, whether it is horizontal or vertically polarity   and, then, the ‘quality’ of the equipment  receiving the signal all have a part to play.