Re: LF: Keyboard Modes for 600 Meters

[John Andrews <w1tag@w1tag.com>]

Dear ++ (Graham), <g>

I think that Olivia uses sequential FSK, not simultaneous tones. I don't 
believe that Jay and I evaluated any simultaneous systems. We did use 
linear PA's during the tests, but that was more for convenience in 
switching back and forth between PSK and FSK systems. The claim is 
generally made that the various FSK modes do not require amplitude 
linearity. It would make an interesting experiment to compare bandwidths 
and perhaps audible keying artifacts between linear and switching amps 
while driving the fairly high Q antennas we use at LF and MF. I'm always 
amazed at how click-free the hard-keyed CW signals are down here.
John A.

Graham wrote:
> Interesting list of modes and tests ,