They tuned it to the typical ham transceiver BW (just like they did
PACTOR-3). THAT is why we need a limit! Ham radios, especially SDR
units, will be able to handle higher BWs - let's get the limit in
place NOW.
Which is all fine and good but *don't* put wideband data on top of the
nearly 60% of amateurs who still use narrow band modes. If you want
2000, 2200, 2400, or 2800 wide data, put it in the part of the bands
where J2 modes of that bandwidth are already permitted.
The Commission has repeatedly held that separating wideband modes from
narrow band modes is proper:
We believe that separation of emission types by bandwidth is accepted
in the amateur service as a reasonable means to minimizeinterference
> on shared frequencies and bands ... (pg 12, FCC 06-149, WT Docket
04-140)
Simply eliminate regulation based on the modulation source - limit
occupied bandwidth on those frequencies currently identified as "RTTY,
data" to 500 Hz or less, allow occupied bandwidth of up to 2800 Hz on
those frequencies between 3 and 39 MHz currently identified as "Voice,
image" with an exemption to 6 KHz for A3E (communications quality
double sideband AM) and prohibit spread spectrum or "sounding". At
that point, amateur radio has maximum flexibility, the opportunity
to innovate and nobody has "lost" any privileges although some
operations might need to move a bit to comply.
After that we can argue about the treatment of "permitted codes"
- what data must be made public and to what extent developers of
new protocols must facilitate monitoring for purposes of self-
regulation.
73,
... Joe, W4TV
On 12/26/2013 4:27 PM, Kai wrote:
Hi Chen,
Right you are - P4 is 2400 Hz BW, not 2200 Hz. So the 2200 of P3 has
already crept up to 2400 Hz. The data from your URL further also makes
my point:
"Special importance was given during the development of PACTOR-4 that
this *could be used without problem on industry standard transceivers
with a 2.4 kHz IF bandwidth ("amateur radio transceiver")*. Due to the
adaptive equalizer, the form of the IF filter curve (as compared against
OFDM, PACTOR-3) is non critical. PACTOR-4 requires only slightly more
SNR in order to equalize even "heavily bent" IF filter curves."
In other words, *it is only 2400 Hz because of today's equipment
limitations!*
They tuned it to the typical ham transceiver BW (just like they did
PACTOR-3). THAT is why we need a limit! Ham radios, especially SDR
units, will be able to handle higher BWs - let's get the limit in place
NOW.
73
Kai
On 12/26/2013 4:01 PM, Kok Chen wrote:
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
_______________________________________________
RTTY mailing list
RTTY@contesting.com
http://lists.contesting.com/mailman/listinfo/rtty
_______________________________________________
RTTY mailing list
RTTY@contesting.com
http://lists.contesting.com/mailman/listinfo/rtty
|