Looking back it seems that up into the mid 1960's Australian dials were marked with call signs, and by the mid 1970's this was replaced by frequency marking. Was there a particular time or legistaltion that resulted in this change, or was this just a result of moving from Australian made to internationally sourced radios?

As far as I have been able to gather the Commonwealth has never required station owners to identify their transmissions by callsign.

There is an international treaty that requires that all transmissions around the world be identified at least once per hour by a name of some sort. EG: The Seven Network calls themselves either Channel Seven or just Seven instead of ATN7, BTQ7, etc.

In radio it is pretty much the same. 2MMM, 3MMM and 4MMM go by the name Triple M and 2FC and 3AR call themselves Radio National.

As far as I know all new licences are still issued with callsigns this is more for management purposes than for station ID.

It is somewhat strange that radio stations around the country continue to ditch public use of callsigns, especially when the nation's top-rated stations have chosen to stick with them. 2GB, 2UE, 2CH, 3AW and 4BC all rank at the top of their target audiences and are amongst the oldest stations overall.

One other thing that has influenced the demise of the all-States tuning dial is the number of radio stations we have now. In 1960 we had only eight stations in Sydney. Now there are three times that many and whilst some have either started on or later shifted to the FM band, these would all still be on the same tuning dial. This space requirement along with the trend towards making the entire radiop fit in your pocket meant that something had to give.

I was somewhat disappointed when 2UW (a station I often listen to) ditched their callsign. They are reported to have broadcasted continually since 1935 when they became the first station to broadcast 24/7. Their callsign is now 2WFM and is publically identified as MIX106.5.

It will be interesting to see what comes with digital radio when it (if it ever) gets off the ground. Assuming that all stations around the country will be required to move to a position in the band allocated to digital radio broadcasting, will new (NLLLL) callsigns be issued or will they be ditched altogether?