Short and stubby
One of these works well in medium to strong signal areas, and has a mag mount. It can be left on the roof at the pointy end. I find it works best in conjunction with an aerial amplifier, typically a 12V one from a caravan accessory place. If we can't pick up anything with this, and we really need to watch something, then the pole comes out with a short log periodic that Nick linked to above. Or if we have plenty of Gigs left on the mifi, watch through the internet.
Sony flat screen TV, works through a 12V - 19V laptop power supply.