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
_______________________________________________
RTTY mailing list
RTTY@contesting.com
http://lists.contesting.com/mailman/listinfo/rtty
|