/"...That is wrong, but that is the status quo, and RM-11708 has nothing
to do with it one way or the other."//
/
Neglecting the consequences of enacting one piece of legislation to the
detriment of existing legislation is both naive and dishonest. It's
equivalent to lying by the sin of omission.
I do expect the Commissioners will read past the "popularity contest"
going on and reject RM-11708.
73 de Bob - KØRC in MN
------------------------------------------------------------------------
On 12/26/2013 2:15 PM, Kai wrote:
Hi Al,
Baud rate does NOT limit BW, except for 2-tone FSK RTTY.
Actually, two tone FSK RTTY is the ONLY digital modulation that
currently has a defacto BW limit under FCC rules. Those limits are 300
baud and 1000 Hz maximum spacing between tones, which would occupy
1500 Hz. No one uses that, but it is a limit.
On the other hand, I can legally use, for example, 16 carriers (or 32
or 64) spaced 1 kHz each, with each carrier containing QAM encoding,
and as long as I strobe the ensemble of those carriers at less than
300 baud, I'm legal - and occupying more than 18 kHz (or 34kHz or 66
kHz) BW. It's a crappy modulation but LEGAL today! The FSK shift
limit doesn't apply because it's not FSK!
The ONLY thing limiting modulations like the crappy ones I listed
above is that VERY FEW receivers out there can handle a bandwidth of
18 kHz (or 34 kHz or more). Most radios can handle less than 2400 Hz
of phase and amplitude-linear BW suitable for modern modulations.
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.
A sore point for me is that the PACTOR (3 and 4) encoding and decoding
are not publicly available -unless you actually buy their modem. That
is wrong, but that is the status quo, and RM-11708 has nothing to do
with it one way or the other.
Kai, KE4PT
On 12/26/2013 12:44 PM, Al Kozakiewicz wrote:
As I said in my own comment, this is a straw-man argument. The
symbol rate has the effect (intended or not) of capping the
bandwidth. Although you are technically correct that the current
regulations stop no one from sending 45.45 baud RTTY using 120 kHz of
bandwidth, NOBODY does!
Also, I thought that when the ARRL amended their filing to drop the
reference to "unspecified digital modes", that effectively removed
Pactor 4 as a permissible mode on amateur band HF if the proposed
rule was adopted. That's not true?
Al
AB2ZY
-----Original Message-----
From: RTTY [mailto:rtty-bounces@contesting.com] On Behalf Of Kai
Sent: Thursday, December 26, 2013 10:47 AM
To: rtty@contesting.com
Subject: Re: [RTTY] Wow - thanks Dr Flowers!
Hi Chen
What a tortured argument he made!!
BIG error here:
*"**So, before the FCC removes the symbol rate and allow higher
bandwidths ..."*
Higher bandwidths ARE already permitted, or more precisely HIGHER
BANDWIDTHS ARE NOT PROHIBITED TODAY, with the exception of two tone
FSK ("RTTY"), which is limited at about 1.5 kHz BW. [My emphasis!].
Today, hams can use 2.8 kHz, 6 kHz, 12 kHz or 120 kHz or higher
bandwidths as long as the symbol rate is below
300 baud, and the emission is confined to the ham band. The ARRL
proposal would limit the BW to 2.8 kHz where none exists today (well
below the 6 kHz permitted in Canada).
73
Kai, KE4PT
On 12/26/2013 5:42 AM, Kok Chen wrote:
On Dec 25, 2013, at 10:35 PM, Rex Maner wrote:
I'm glad I know how to press the ENTER key. I sure don't have any
idea what this person is talking about , but it sure sounds
informed.( I Think )
I believe some of the points that Andy made are (I paraphrase, and
also drill down a bit):
1) the Symbol Rate is not about the ARRL strawman of "spectral
efficiency." The ARRL themselves have in the past said that spectrum
efficiency is not a goal of amateur radio (and neither does
§97.1(a-e)), and now the ARRL petition claims that it is, when
arguing for wider bandwidths.
2) based on past FCC rulings, the Symbol Rate is never about
bandwidth either, but about hams being able to self regulate.
a) self regulation means that everyone else has to be able to
"read the mail," (literally :-)
b) this means that I should be able to copy a signal even when
conditions are poor,
c) well, if that is so, high symbol rates simply don't work
anyway, since the symbol rate has to be kept low even though the
path between the two parties is good, so that a third party (like an
OO) can still monitor the conversation.
d) by complaining that Pactor-3 is not efficient, the ARRL
obviously don't even understand how the ionosphere works (Andy cites
the Maslin book).
3) modern digital modes use what are called (by Harris, for example)
"Serial Tone" modems.
a) you cannot use low SYMBOL rates (like the 100 baud in Pactor
3) and keep adding subcarriers to get higher DATA rates,
b) so, you use something like 64-QAM (QAM is a mix of PSK and
amplitude modulation -- ASK), and you run at really high symbol rates,
c) to get high symbol rates through HF propagation when
conditions are poor, the Serial Tone modems equalizes the channel,
d) to do equalization, they periodically send a long pseudo
preamble (PN) sequence (example Andy gave is 176 bits long, used in
STANAG 4285) .
e) the receiver takes the PN preamble and performs an
autocorrelation, and from that derives a real time equalization of
ionospheric distortion.
f) but here is the crux: unless the PN generator is openly
published, it is equivalent to encryption, (which serves a dual
purpose with the mil STANAG modems)
g) so we are back to hams not being able to self regulate
again, since we cannot read the effectively encrypted mail.
So, before the FCC removes the symbol rate and allow higher
bandwidths, they should make sure that Amateurs have the tools to
read the mail. By citing Pactor-4 in the petition, the ARRL must
think that Pactor-4 satisfy the "read the mail" condition, but Andy
thinks that it does not. Pactor-4 does not satisfy the conditions
needed to be used in the Amateur service.
Andy also points to the fallacy with people who expect privacy when
they use the Amateur service to forward email, since Amateur Radio
principals have been that messages that are carried by the service
must be transparent. By making encryption open, these email users
will at least not be misled that they have any privacy when they use
the Amateur service to forward their email. Since the principal is
already embedded in §97.309(a), the FCC need not make a new ruling
but just re-affirm it, since "it is obviously a point of confusion"
to many parties.
Andy also called the 2.8 kHz part of the petition "strange," and
added that the ARRL has not specifically said why they think there
is a "tangible need" for it. In my own comment, I had used
"arbitrary and capricious" to describe the 2.8 kHz number -- in
lawyerese, a rule is arbitrary if it is not supported by logic or
the necessary facts; a rule is capricious if it is adopted without
thought or reason or is irrational
(http://definitions.uslegal.com/a/arbitrary-and-capricious/ ).
73
Chen, W7AY
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