I have never applied for planing, and I note loads of people around here who seem to have 27 Mhz ariels, did consider 2 meter but only one guy I can reach, so seems a little pointless.
As for TV in a narrow boat or caravan I can see why omnidirectional, but in the main we want to only get signal from one mast, so directional aerials both increase signal from a selected mast and decrease signal from others. In the last house, aerial on the wall to mask it from Winter Hill, so only got Moel-y-Parc, but here Moel-y-Sant is rather useless, given up, and use satellite only.
One can extend cables, and after the pre-amp should not be a problem, however it does not say if horizontal or vertical polarised, main transmitters and repeaters use different polarisation, vertical is OK as a simple dipole, but horizontal need a halo type aerial which have a lot of losses. Distance does matter, leaving Sizewell 'B' using SSB I was comparing signals between halo and 7/8th whip, and as expected up to Cambridge the halo worked best, but then I got a black spot, and by time approaching M1/M6 interchange, on way to North Wales, the 7/8th whip was actually working better. Most do not use 2 meter sideband mobile, it was an experiment.
However, it depends on the other station as well, he had a rather good horizontal beam. Falklands uses horizontal mobile FM 2 meter, but most use vertical for mobile.
The whole idea of horizontal or vertical polarised transmitters is to stop the repeaters interfering with the main transmitters, so seems odd not to state which the aerial is. FM, DAB & Digital TV seems odd, as the TV carrier signal is not digital or analogue it does not matter, it would be like saying black and white receiver, does not matter what colour I paint the aerial, which is the apparatus which receives the signal, so it is the decoder circuit which allows one to view in black and white (monochrome) or colour, not the receiver (aerial).
This
is the important bit, the cable and any amp or filter must be able to take DC, many wall plates include a brade break to stop static shocks when handling the cable, and these will not allow DC to pass.