Radio amateur operators in Australia have been granted access to the new 630 m band. The frequency range is 472 kHz to 479 kHz. The maximum EIRP allowed is 5 W pX and the maximum bandwidth is 2.1 kHz. There are two exclusion zones around the Exmouth NDB (1000 km) and Timor NDB (2000 km). A map showing the exclusion zones can be seen here (courtesy of Mike VK2IG).
I have built a valve transmitter for 472 kHz . I am also building a simple, non-linear, transmit converter.
630 m activity coordination and relevant discussions take place in the 600m yahoo group.
I am also building a DC receiver. So far, there is a simple bandpass filter but more details will follow soon.
Finally, there is a page on a small magnetic loop antenna with 10 turns, tuned to 475 kHz.
Grabbers are computer systems connected to receivers that continuously monitor a part of the spectrum, posting every few minutes the latest spectrogram on a page accessible via the internet. They are valuable tools to transmitter builders as they provide immediate feedback on the performance of their transmitter. They are also valuable to operators wishing to fine-tune their receive setup, by providing information on signals on air in real time.