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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