On Feb 17, 2005, at 3:55 AM, niddy noddy wrote:
> SO what exactly is "OOK" ??
OOK On-Off Keyed (one carrier, keyed on and off, e.g., CW)
FSK Frequency Shift Keyed (keying between two different carrier
frequencies, e.g., RTTY)
PSK Phase Shift Keyed (keying the phase of a carrier, e.g., PSK31)
With FSK, the modem's duty is to guess whether it is more likely that a
Mark was sent, or whether it is the Space that was sent. Guessing
wrong causes a bit error.
When OOK is used in an FSK modem, it is asked to guess what was sent
based on only inspecting the mark tone ("Mark-only" detection) or based
on only inspecting the space tone ("space-only" detection).
Since you are only looking at the power from one of the tones, copy is
degraded compared to looking at both tones. However, if one of the
tones is under severe QRM and the other is not, detection with
Mark-only or Space-only can provide usable copy while Mark/Space
detection does not print at all.
73
Chen, W7AY
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