Over the past few years, tremendous advances have been made in weak signal communications 
on the VHF and UHF bands using computer generated data modes. These modes enable 
communications at or below the noise floor. Amateurs with modest stations are now making 
contacts over thousands of kilometers via EME and Meteor Scatter using these "new modes". 

However, often these very weak data signals can not be detected by ear, which makes them 
incompatible with normal analogue SSB or CW signals. There have been instances of 
interference caused by SSB operators who obviously can't hear the data signals.
The recent EME Conference held in Germany recommended the creation of world-wide VHF and 
UHF subbands for JT-65 - the weak signal data protocol. The suggested segments are 
50.185 to 50.195 MHz on 6 meters, 144.115 to 144.135 MHz on 2 meters, 432.060 to 432.070 
on 70 centimeters and 1296.060 to 1296.070.
(VK4DU, for the national WIA)
from AR-Newsline

The maximum bandwidth determines the maximum spectral width (-6 dB points) of all emissions
allowed in a segment. The mode indicates the modulation methods (e.g. telegraphy, telephony,
MGM, etc.) allowed in a segment. M(achine) G(enerated() M(ode) indicates those transmission 
modes relying fully on computer processing such as RTTY, AMTOR, PSK31, FSK441 and the like. 
from IARU-Bandplan