Kok,
Yea, I also don't see the tie to "modern" in that none of the modern methods
are wide banded. Only the stuff for mail relay seems to be. I actually
don't understand how winlink mail makes sense - I can see and emcom
justification but that's not the selling point. Free email via HF seems to
be the selling point.
I do find it pretty interesting that of the 5 ARRL signatures on the
Document 28 petition, the chairman and second undersigned are promoters of
the Winlink system. And at the same time, none of these guys seem to be
RTTY contesters - only K1ZZ sent a log in the 2012-2013 ARRL RTTY RU.
73/jeff/ac0c
www.ac0c.com
alpha-charlie-zero-charlie
-----Original Message-----
From: Kok Chen
Sent: Thursday, November 21, 2013 11:04 AM
To: RTTY Reflector
Cc: Jeff Blaine
Subject: Re: [RTTY] ARRL attack on current RTTY users
On Nov 21, 2013, at 8:26 AM, Jeff Blaine wrote:
There is a lot of "modernization" and "flexibility" listed - but who,
beyond the PACTOR guys, would actually benefit from this change. Figure
that out and we can likely connect the dots from that group to this
decision.
Unless the words "modernization" and "flexibility" are synonymous with the
phrase "more data bandwidth," the ARRL proposal simply don't make any
technical sense.
As I mentioned in an earlier private email to another reflector participant,
take a look at all the advancements towards getting the most miles with the
lowest power. You need not look further than Joe Taylor's modes.
http://www.physics.princeton.edu/pulsar/K1JT/index.html
If you include the also widely used PSK31 (very good for folks with small
antennas and low power when propagation is good) the focus on narrower
bandwidths goes back for at least two and a half decades.
These folks had the freedom to use higher symbol rates and wider bandwidth,
but choose not to.
Technically, you can use wider bandwidths to counter selective fades due to
multipath in Rayleigh channels (best model for HF that has been used for
decades now). That is addressed in modern modes with good forward error
correction (FEC) and longer data frames. And even when you use simple two
tone FSK, it has been known by amateurs since the 1960s that 170 Hz is
already wide enough to derive information to apply a good automatic
threshold correction to FSK. As I mentioned in my "RTTY Demodulators"
article,
"In a February 1964 article in the RTTY bulletin, Frank Gaudé reported that
there is actually no significant difference anyway between the amount of
selective fading between a wide shift and a narrow shift signal down to the
170 Hz region."
So, the need for wider bandwidths has nothing to do with finding better
modes for HF communications. It does allow you to push more bits per second
through the channel.
BTW, you can include references in your comments to the RM, and the
references can include Web links, references to RTTY Bulletins from the
1950s, or email to your kids, if those are pertinent. Please feel free to
do all the web research that you need and include references that you decide
are pertinent to include in your own comments.
73
Chen, W7AY
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