Hi Joe,
It squares this way. PACTOR uses multiple tones, but not tone shifting, so shift
is zero.
PACTOR baud rate is around 100 Hz, so it is well below the 300 Hz max, so
legal.
The key is that PACTOR-III is not FSK. It is more like OFDM - carriers
that carry D-BPSK or D-QPSK modulation.
PACTOR chose 2200 Hz occupied BW (not 2400 - that's an ARRL error) exactly
because it fits in the SSB passband of typical ham radio. Theoretically there
is no statutory BW limit for that kind of scheme as long as baud rate is less
than 300 Hz! As more radios show up with "flexible" bandwidths greater than
today's
2200 - 2600 Hz, there will be the temptation under current rules to fill that
bandwidth.
Only a BW limit will stop them, because wider radios are coming -- they are most
useful
for JT65 / JT9 and PSK operators at the moment, where observing a 4 - 6 kHz BW
in an SSB
radio is very useful.
That is the biggest reason why I favor dumping the baud rate limit in
favor of a BW limit.
Yeah, the situation can be VERY ugly if we manage to kill the ARRL proposal and
radios like software defined radios with wider SSB bandwidths become more
prevalent, and it gets ugly if 2800 Hz passes - but ugly only when HF radios can
handle 2800 Hz BWs. Most can't, today's typical radio BW is around 2.2 to 2.6
kHz.
I believe our best course is to sway the FCC to choose the ARRL proposal, but
cut
the BW to 2200 Hz (and 2800 above 28 MHz).
No current user is excluded (Commissioners have stated that excluding current
users is not
in the public interest), and we cap the BW.
73
Kai, KE4PT
On 11/24/2013 9:28 PM, Joe Subich, W4TV wrote:
If it is 2.4 KHz wide, it can not be legal ... how can one square
2.4 KHz occupied bandwidth with a rule that states a combined
criteria of 1000 Hz and 300 baud which works our to 1500 Hz?
This is *exactly* the reason that comments need to stress a 500 Hz
bandwidth limit for all "RTTY, data" emissions in the spectrum
covered by 97.307(f)(3) and 97.307(f)(4) to be consistent with
"traditional radiotelepinter bandwidths" as the Commission held
in "Further Notice of Proposed Rule Making, 43 Fed. Reg 36984".
The Commission believed that a 1000 Hz shift and 300 baud symbol
rate would assure emissions consistent with "traditional radio-
teleprinter bandwidths" would provide for bandwidths consistent
with then standard operating practice. Unfortunately, there was
at that time no use of composite FSK/PSK systems, multi-tone
systems, etc. and their use has exploited a regulatory loophole
*that needs to be closed* lest these wide bandwidth and inefficient
modes cause irreparable harm to traditional narrow bandwidth modes
which are limited to frequencies where F1 emissions are authorized.
73,
... Joe, W4TV
On 11/24/2013 9:01 PM, Kok Chen wrote:
On Nov 24, 2013, at 5:02 PM, Joe Subich, W4TV wrote:
PACTOR III is *NOT* currently permitted under the rules. Its use has
been *overlooked* by enforcement organizations as it *absolutely* can
not be justified under the *dual standard* in 97.307(f)(3) which has
both 300 baud and 1000 Hz shift limits.
That is not true Joe... please don't make that mistake in your FCC filing.
At all SL levels, Pactor III's symbol rate is fixed at 100 baud (yes, not
even close to 300 baud). (Don't confuse Symbol Rate (baud rate) with data
rate (bit rate)).
Pactor III is not 2 tone FSK, so the FSK shift rule does not even apply
(makes no technical sense since there is no frequency shift happening).
Pactor 3 SL1 (the slowest rate) consists of two synchronous PSK signals (not
FSK), that are separated by 840 Hz. 840 Hz is the maximum tone separation
for Pactor 3 (if you want to apply the term "shift" to the signal). As more
tones are added (SL2, SL3, etc), the tone separations become narrow, and at
the narrowest, there are 18 tones, separated by 120 Hz from one another.
Pactor 3 SL1, 2 and 3 uses binary PSK, and Pactor 3 SL4, 5, 6 uses Quadrature
PSK.
It is much clearer if you go take a look with a panadapter or a waterfall, or
if you can, in I/Q phase space.
Pactor 3 SL1 looks like two broad indistinct tones that are 840 Hz from one
another, with a distinctive gap in between them. It is quite unmistakable
once you see it on the waterfall.
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
|