[RTTY] Wow - thanks Dr Flowers!

[Kok Chen]

On Dec 26, 2013, at 12:15 PM, Kai wrote:

> PACTOR-4 (which occupies about 2200 Hz BW, just like PACTOR 3 which is in use today) would indeed be permissible once the 300 baud symbol rate is removed.

Pactor-3 has 2200 Hz bandwidth (2K20J2D), but Pactor-4 is 2400 Hz, per SCS, not 2200 Hz.  See

http://www.p4dragon.com/en/PACTOR-4.html

Pactor-4 SL1 has two subcarriers.  Pactor-4 SL2 through SL10 are all single carrier, at 1800 baud.  SL9 and SL10 are 16-QAM and 32-QAM, thus 1800*4 (7200) and 1800*5 (9000) bits/second raw data rate.  See 

http://www.medav.de/fileadmin/redaktion/documents/English/vd_PACTOR_demodulator.pdf

So, the ITU emission mode of Pactor-4 actually changes as you switch SL levels.  But the bandwidth of Pactor-4 does not change to same the degree as the bandwidth change for Pactor-3 (from 500 Hz to 2200 Hz).  

Further, notice that SL2 through SL4 have a spreading factor, so the 1800 baud actually produces lower than 1800 bits/second raw data (bit) rate.

It is going to be interesting to see if Pactor-4 SL2, 3, and 4 can be legal on ham bands since they involve some sort of spreading.  DQPSK is often implemented with a direct sequence spreader.  If/when they reveal the details (to work around "unspecified codes") we will know if these SL levels are mathematically equivalent to direct sequence spread spectrum.  

Lawyers, start your billable hours clocks :-).

73
Chen, W7AY