Getting the most out of our CP100s

Hoping I can get some help. We are currently using Motorola CP100 radios in the UHF band for our gravel pit, however the signal is lost when our operators reach the far edge of the facility. Granted, the radios are old, but is there a different kind of antenna that we could use to increase range? The max distance between radios is never more than 3 km, but there is some terrain and trees that contribute to the interference. Perhaps we might install a tall radio tower at the office? Any help is appreciated.

3km between radios working direct to each other is actually pretty good. The answer is a repeater with an antenna on your office - even better if the office is in the middle of the site, but realistically, that never happens. The higher the antenna/antennas, the further the range - the idea is that with a repeater, everyone’s radios only has to go to the antenna on the office - so range is improved drastically. Cost wise? A UHF repeater is between 750-1500 (UKP) new, but with people moving to digital, second hand repeaters are often available. This of course depends on your licensing system, and if you have the reprogramming facility yourselves? If you don’t, then whoever you use to reprogram all your radios might as well supply you the repeater, filters, cable, antenna(s) and mast you need. The CP100 are legacy radios now, so not everyone can reprogram them.