In Off-roading or "Overlanding", it is quite common to not really only on the availability of the mobile phone network, but to use radio communication.
Basically, you got three options:
CB (Citizen Band, transmitting analog in 27 MHz across 40 to 80 channels using around 5 to 25 Watts of power),
PMR, transmitting around 440 MHz with a limited amount of power (usually 0.5Watts only)
and finally, HAM or Amateur Radio, also commonly using the 440 MHz range but with much higher transmission power (up to around 200 Watts in mobile units).
CB and PMR do not require a license, Amateur Radio does (but it is fairly easy to acquire and definitely interesting to learn about).
As CB has the range advantage in terrain over PMR, we opted for CB radios. They are also very inexpensive (about 100 EURO). We chose the model President Bill II which as a clever Auto-Squelch feature and configurable background lights to suit your car/preferences.
The tricky part is finding a good antenna that can work on the California's aluminium roof. On a normal car roof, placing the antenna in the middle of the car roof will provide a sufficient ground plane. On an aluminium roof, that is not an option.
Luckily we found select an antenna which does not require a ground plane. The one we chose works fine attached to our Terranger Dachgepäckträger Leicht (which also happens to be made out of aluminium).
K-PO Omega Firestick 27 NGP (No Ground Plane), price around 75 EURO.
For our mobile (handheld) units, we chose two Randy III's, also by President. These are way more compact and better battery-wise then the old clumsy models from the 80:s & 90:s!
Good radio (online) shops:
In Germany:
Diesner Funk: https://diesnerfunk.de/
Neuner Funk: https://www.pmr-funkgeraete.de
In Sweden:
Limmared Radio: https://butik.limmared.nu
