Back in spring 2018 Rolf, DK7FU, contacted me about the key click from DB0HRF, on 2 m using PI4, that disturbed the DR9A contest group 172 km away. I made and installed a new S/W on the AD9912 driver that is able to perform linear intermediate steps when shifting from one tone to the next. We eventually settled for four intermediate steps. The steps reduced the key clicks by ~12 dB. More steps did not provide any significant difference. With 100 steps the signal sounded like a slide guitar straight out of Nashville. 100 steps also fooled PI-RX so this was not feasible at least with the speed of change implemented and over the K = 40 tone spacing.

With an AD9912 clocked at 1 GHz https://rudius.net/oz2m/ngnb/dds.htm changing frequency is limited by the SPI speed. But Gaussian steps could easily be implemented. On top of my head I believe that some of the AD99xx DDSes can do some sort of Gaussian steps themselves in addition to raised cosine RF amplitude.

Bo
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