[Elecraft] K3 data mode operation?

[Dave G4AON]

I've been trying data with my K3 and find the "Data A" mode works OK for 
RTTY (unfortunately with only basic passband filtering from the K3). I 
was using audio from a sound card fed via the line in socket. When the 
K3 is set for data mode "AFSK A" which implies RTTY mode with AFSK (and 
gives improved dual passband filtering as shown by the filter display), 
there is no transmit output for audio into the line socket - which 
worked perfectly when set to "Data A". Under advanced operating features 
(page 31 of the current manual) there is no mention of data 
transmission, only reception....

There seems little interest in data via the RS232 lead, currently it 
doesn't work properly on receive because of mixing frequency and other 
"housekeeping" information with the received text.

I've not yet tried direct keying on mode "FSK D", this might work...

Any thoughts on data modes with the K3 in general, or have I just hit 
features that are still to be implemented with data via RS232 and the 
"AFSK A" mode?

73 Dave, G4AON
K3/100 #80