[digitalradio] MT63 is NOT spread spectrum!

[KH6TY]

MT63 is PSK, and if you go to this link 
http://f1ult.free.fr/DIGIMODES/MULTIPSK/MT63_en.htm you can see how the 
carriers are fixed in frequency and not random in frequency. In fact, 
the description of MT63 is, "DBPSK on 64 carrier tones. The tones are 
separated by 7.81 Hz for the 500 Hz bandwidth, 15.625 Hz for the 1000 Hz 
bandwidth or 31.25 Hz for the 2000 Hz bandwidth mode. The data is 
encoded using a Walsh-Hadamard transform to provide high degree of 
redundancy". The tones (i.e. carriers on a SSB transitter) are in a 
FIXED place and NOT randomly assigned a frequecy, so MT63 is NOT 
frequency hopped, or spread spectrum, even though it can be as wide as 
2000 Hz.

The spectrum of MT63 shows this very clearly. Compare that to the 
spectrum of ROS 16 and 1 baud of 2250 Hz width.

73 - Skip KH6TY