Nils which Northern Terriotary roads do you have in mind???
UHF radio is very short range, depending on the terrain up to 5 or 10km safe with hand held units even shorter and will either get you in contact with 4WD travellers or local cattle station out workers
An EPIRB is used for emergency situations only as a last resort and will get you help ASAP. In the outback that can take a while as there are huge distances to cover, but they will investigate.
A HF radio has national coverage and is suitable for the 4WD traveller but is out of the question for the motorcycle traveller due to it's physical size
The other option to consider is a Sat Phone that supposedly has national coverage. These can be hired locally depending on your starting point.
Depending on how remote the roads are you intend to travel, it would be very unusual not to see another vehicle within a 24 hour period
In winter you will see a lot more people travelling than in summer when temps are very uncomfortable
Go to 4WDing, Camping & Caravanning around Australia @ ExplorOz
for remote road condition info
Fuel range is normally more of a problem than communications
I have had a few drinks, so I hope this makes sense, Glen
Feb 2014, currently travelling the America's on a Tiger 800XC
Live every day like it's your last, one day you'll get it right!!!