[hpsdr] Mercury sampling rate

[Phil Harman]

Most interesting discussion regarding Mercury sampling rates.  As Greg 
pointed out, we actually don't require a sound card  for Mercury since there 
is a D to A converter on the board. You can also use the D to A on Penelope 
or a Janus board.

There was another reason for using an VHF clock that would divide exactly to 
48/96/192kHz in addition to compatibility with sound cards.

When developing Penelope we wanted the CW performance to be the best we 
could provide. Since the D to A and A to D clocks for the receiver audio 
were from the same phase locked source then we would never run into the 
buffer over/under run issued that others have mentioned.

However,  PowerSDR expects that  the CW timing will be based on a 48kHz 
clock.  In which case any clock departure from exactly 48kHz resulted in an 
accumalated error that would place a 'blip' in both the CW sidetone and 
transmitted signal.

We did consider a 'fix' for this with Bob and Frank but concluded that life 
would be much simpler if we used a VHF clock that had an integer divide to 
48kHz.

Perhaps there  is a technically elegant way of solving this issue but we 
chose the simplest one.

73's Phil...VK6APH



 1208064208.0