At 11:19 PM 10/31/2009, Kok Chen wrote:
><snip>
>The point is that steam RTTY requires much higher SNR to operate under
>propagation conditions that includes echos, than it does under
>propagation conditions that includes selective fades (that is why the
>experimenters eventually chose more than one tone for RTTY in the
>first place -- early amateur RTTY experimenters had used OOK (one on-
>off tone), but went to FSK to avoid selective fading). <snip>
A comment - I don' t think the early experimenters "eventually chose"
FSK - OOK was the only legal mode. We were not allowed FSK on the HF
bands until Jan 1, 1953 by the FCC. FSK use started as soon as the
FCC allowed it. Interesting reading of early days at
http://www.rtty.com/history/w6owp.htm
Jerry W4UK
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