M.A.M.I. has license free ISM band radio transmitters capable of sending signals up to 6km depending on terrain without the need of a frequency license, this distance can be extended with the use of Repeaters.
The UHF range of radios are available in 4 and 8 channel versions with the option of external antenna
You have the choice of having the transmitter and antenna integrated or alternatively have an external connector to place the antenna in a better location
It is possible to cluster groups of the UHF radios in an area and retransmit via high power VHF radio over 50km or over GPRS to anywhere in the world!