Ron Stordahl wrote in a message to Mike Bilow:
RS> I have been reading this thread and wondering if a
RS> description, a user level description would be fine, of the
RS> various modes you have been discussing. Pactor, Pactor I,
RS> Pactor II, Clover, etc.
Basically, they are various schemes for using FEC (forward error correction),
ARQ (automatic request for repeat), adaptive modulation, or combinations of
these techniques. For example, Clover changes its output power, bit rate, and
modulation format in response to continuous monitoring of link quality, slowing
down and using more power as the link gets worse.
RS> Personally I have never understood what is wrong with HF
RS> Packet that could not be cured by a lower baud rate, perhaps
RS> a change in modulation method to PSK etc. My impression is
RS> that the protocol is solid, but that FSK is just not up to
RS> 300 baud with 200 cycles shift on HF.
No, the protocol is abysmal. FEC and ARQ are essential to reliable HF data
communications. Adaptive changes to bit rates and output power are nice. The
actual modulation method is the least of it.
RS> I have done a bit of
RS> HF Packet and believe the thruput would actually increase
RS> with a lower baud rate.
Sure it would, and less people would be killed in road accidents if the speed
limit were reduced so that cars could go no faster than pedestrians.
RS> The very effective PSK31 suggests
RS> to me that a switch to PSK for HF Packet may we warranted.
FSK and PSK are essentially the same thing as far as this issue goes, and you
can regard FSK as a special case of PSK. I don't want to get into this issue
in detail because experience has shown that it provokes religious arguments,
but the math is clear.
-- Mike
