I have a fair bit of experience operating /P from the top of various hills around here - but with voice - not specifically ATV (yet
).
However, FWIW, I will contribute my description of operating, some of which will be relevant to /P ATV ops...
Power-wise, to avoid becoming stuck miles from anywhere with a flat battery, I have a ~100Ah 'leisure battery' in the back of the truck, completely unconnected with the vehicle electrics (I operate in the 10W max category of the UKACs and the battery will normally last 5 or 6 sessions of 2.5-3 hours, comfortably. (Obviously, operating 5.6GHz low power ATV with WBFM and/or DATV/ATV at higher powers will have a different consumption porfile, but the worst that will happen is that you run out of QSO time, rather than being stranded, after dark, on a remote hilltop, as could be the case in the UKACs
)
Antennas (a mottley collection of yagis/moxons for the lower bands (50MHz-2.3GHz) are held aloft by means of a 5m (4m if windy
) sectional lightweight alloy pole, held at the bottom by a drive-on plate with a tubular socket. If the mast needs additional support, I have a bracing piece extending from the roof rack. For microwave ops with flat panel and small dish antennas (3.4-10GHz), I have a selection of 'tripods' (originally intended to support PA or DJ speakers (not Dutch and German ones
) or a Radio Structures Ltd tripod which will take a 1.5" 4m pole. The assembly is somewhat wobbly with the 4m pole in it, so I tend to use a shorter length, particularly if windy.
Power distribution for the lower power items (microwavey bits) is via a small SOTABeams distribution box with Anderson PowerPole connectors, fed from the aforementioned battery. The higher power radios' power leads are routed directly to the battery via PowerPole connectors.
Antenna cables are fed in through a partially open window, with length of pipe insulation slotted over the top edge of the window glass to allow the cables in, but keep the rain and the draughts out.
Radio equipment is perched on a shelf which fits between the top of the dashboard and the headrest of the passenger seat (seat reclined to get things level), and my tablet that I use for logging is held in a holder designed to fit between headrest supports - for back-seaters to enjoy films - but which fits neatly enough between the spokes of the steering wheel.
At present, antenna rotation is via the armstrong method, but I'm hoping to have my ProSisTel rotator rebuilt later this year which will make things somewhat drier on most evenings. This will be fitted at the bottom, and rotate the whole mast. I'm hoping before too long to have some sort of pump-up mast attached to the back corner of the vehicle, which will make getting the antennas aloft a bit easier, but will have to re-consider rotation schemes if this happens.
Just a few ideas - hope thy are of some use.
John