-----Original Message-----
PA must be linear. Is this a though requirement for the
present crop of PAs
around ? How much would this requirement be of obstacle to
the adoption
of such a scheme (which could also be FEC corrected...). TNX
73 Alberto
With the present designs a real killer !
Switching transmitters achieve well over 90% efficiency, and a
conventional linear design would have 78% absolute maximum, more like
50% in reality. With kW outputs, that's a lot of heat to get rid of.
The efficiency issue is why so many commercial LF transmissions use
constant amplitude MSK now, having changed over from bandwidth hungry
FSK. PSK, to be social, needs amplitude tailoring otherwise this
would be the mode of choice. We can get away with using PSK without
any complaints as we are using very low data rates, so the sidebands are
not a serious problem, but there all the same.
Hence my proposal for two sequential tones for a (tongue in cheek)
visual human decoded system.
Or a slowed down narrowband version of Piccolo.
Isn't is about time some more LF operators tried BPSK - I've no one to
listen out for ! But we'll have to find a new frequency, Larry is
established on 137.79 now.
Andy G4JNT
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