Digital radios in a Mountain environment.
For roving applications there are no fixed repeaters with known coverage areas and known black-spots. Coverage is dynamic and highly dependent on the location of each end of the radio link. A bit of high ground in the way will block coverage but sometimes reflection and refraction can give surprisingly good coverage particularly at VHF frequencies.
The one big advantage the mountain radio user has over the low country radio user is they can quickly gain height and improve coverage significantly.
All this means the mountain radio user has to be skilled in assessing where in the terrain radio coverage will be found and where transmitting will be hopeless.
Choice of radio.
Weatherproofing is often a concern however most quality radios are built to withstand temperate climate downpours even if they are not submersible.
Wind over the microphone can be a problem. It can be dealt with by turning your back to the wind, by putting the radio in an Aquapac which shields the mic or using a DSP microphone processor such as found on all digital radios.
Digital or Analogue
Digital radios used in digital rather than analogue mode gives some important performance differences compared to analogue radios: Aside from the advantages of DSP, Digital mode gives clear, noise free audio up until the signal disappears. But the drop-off is sudden, unpredictable and usually without warning.
Although analogue radios become noisy as the signal becomes weaker this increase in noise is a reliable indicator of the signal strength. This offers a huge advantage to the hill user as it can give them the information to choose if the need to move (usually higher) to improve communications.
VHF or UHF
VHF gives marginally (rather then spectacularly) better hill coverage due to its longer wavelength which seems to reflect and refract better than UHF.
Licensed radios transmit on higher power which in theory should give better coverage than lower power licence-free radios. In practice the negative effect of the terrain has far more effect than an increase in radio power can ever overcome.
Pan European Use
For non UK use a UHF PMR446 radio is the only practical option as there is no such thing as a licence-free VHF radio and licensing a VHF radio in multiple countries is extremely expensive and complicated.
If you are intending to use your radios across Europe then good quality PMR 446 radios are ideal. Mostly these are analogue but there are a few digital versions now available some of which have DSP even in analogue mode.
If you have a more 'Professional Budget' and not intending to use radio outside the UK then a licensed radio may give better performance especially if it has DSP in analogue mode.
Whatever radio you decide to use it is essential that you familiarise you and your colleagues with how coverage is affected by the terrain. There is only one way to do this; Get out there and use them!.