Dave,
The answer to your question is no for MT63, as it is nearly just as wide
as ROS 16 baud, but will stop decoding at -8 dB S/N for the 50 wpm mode,
Contestia 1000/64 at -13 dB S/N at 30 wpm, and Olivia slower at 15 wpm,
but probably around -15 dB S/N. PSK31. PSK31 works down to -11.5 dB S/N
at 50 wpm, as a comparison, but is only 31 Hz wide.
The point is that for QSO's (which ROS does), not messaging (what WINMOR
does), fast speed is not needed, because people usually cannot type more
than around 50 wpm (the design goal for PSK31). For messaging however,
you sacrifice minimum S/N for speed. You can get an idea by looking at
the 1 baud mode of ROS, which is extremely slow, even for QSO's, but
good just for exchanges, like in WSJT or moonbounce. This is where ROS
has the greatest potential and where its wide width is not important
because there is so much space at 70cm and 23cm. Otherwise, on HF, the
same long-distance QSO's can be accomplished in much, much, less
bandwidth, and probably just as effectively. I have often worked the
South Pole, Japan, Australia, New Zealand with only 900 mw and PSK31 on
20m and the bandwidth was only 50 Hz maximum. If conditions are at all
favorable, it does not take much power on the higher HF bands to go
around the world.
For UHF, and short exchanges, ROS is probably the best performer in a
bandwidth of 2250 Hz, but the speed is very, very, slow. That is why the
macros are like WSJT macros. It just takes too long to exchange much more.
There is really no rationale for using ROS 16 baud on HF, as wide as it
is, because our ham bands are shared, and spectrum hogs leave no room
for others. However, on UHF, there is, and that is where ROS, with SS,
is not counter-productive, but has the most promise.
On UHF, we could use ROS, but it does not hold up well under Doppler
Spreading, so we have settled on Contestia 1000/64 at 30 wpm as the best
performing mode, decoding right down to the noise threshold, when even
CW is hard to copy by ear. ROS simply failed to print when Contestia
1000/64 was printing 100%.
Your point is well made, but there is a advantageous application for
ROS, and that is on UHF for EME. Up there, it is legal for US hams to
use also.
73 - Skip KH6TY
Dave Sparks wrote:
More importantly (to me, at least) is Spread Spectrum the most
effective or
efficient way of using a given amount of bandwidth to deliver a given
data
rate, from a weak signal point of view? IOW, would ROS work better than,
let's say, MT-63, WINMOR, or Olivia if those three modes were adjusted to
use the same bandwidth and data rate as ROS? If it were open source, I
would have included Pactor-3 in that list, too.
If not, then using SS is counter-productive as well as legally
problematic.
(I'm not implying that ROS is SS, BTW.)
--
Dave Sparks
AF6AS
--------------------------------------------------
From: "Trevor ." <m5...@yahoo.co.uk <mailto:m5aka%40yahoo.co.uk>>
Sent: Wednesday, June 02, 2010 2:29 PM
To: <digitalradio@yahoogroups.com <mailto:digitalradio%40yahoogroups.com>>
Subject: Re: [digitalradio] What is here Spread Spectrum and why and
what is
not?
> --- On Wed, 2/6/10, KH6TY <kh...@comcast.net
<mailto:kh6ty%40comcast.net>> wrote:
>> The FCC engineers have performed the same spectral analysis and
>> informed the ARRL that the mode is truly spread spectrum.
>
> That's interesting, the FCC have said they they did not give
judgments on
> individual data modes, it's up to the operator to decide.
>
> Who were the FCC engineers you mention, where is their report and
who in
> ARRL HQ did they communicate with.
>
> 73 Trevor M5AKA
>
>
>
>
>
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