Extensive tests on 70cm using ROS 16 baud spread spectrum have been
disappointing. ROS appears to be unable to survive the Doppler shift and
Doppler induced "flutter" so prevalent on that band. The hope was that
ROS 16 baud would make traditional communications possible that were
difficult on SSB phone because of the Doppler shift and "flutter".
However, the tests show that Olivia 32-1000, in half the bandwidth, and
Olivia 16-500, produce print when ROS only prints garbage. This,
together with the fact that both stations must be within 400 Hz of each
other before even trying to communicate, instead of being able to tune
with the mouse as is possible with Olivia, makes it very difficult to
achieve a QSO on 70cm using ROS. Olivia has therefore proven to be much
more successful than ROS on UHF.
Tests using the ROS 1 baud variation will be made next, but the slow
speed of that mode is more suited to EME communications than normal QSO's.
In two weeks of monitoring ROS 16 baud on 20m, there has been only one
observed case where the S/N was under where Olivia 32-1000 can decode,
so even on HF, there does not appear to be any justification for using
such a wide mode, even if spread spectrum were permitted on HF in the
US. Just use Olivia or MFSK16 instead when band conditions are poor. The
new narrow band ROS modes were not tested, since a mode to do better
than Olivia is what is needed, and the spread spectrum mode of ROS held
the best hope. As it stands, only CW is better than Olivia under the
worst conditions, and only when copying by ear, but CW is only a little
better than Olivia 16-500. We have also found that the more narrow
Olivia modes (i.e. < 500 Hz wide) are also too greatly disturbed by
Doppler to be useful either.
If anyone is within 200 miles of FM02, has 100 watts and an antenna gain
of 17 dBi or greater, and would like to try ROS 16 baud on UHF, I am
available to do that.
I promised to post the results of our attempts to use ROS on UHF on this
reflector, and this is what we have found. So, it looks like Olivia is
currently still the best digital mode to use on UHF, VHF, or HF for
normal (not EME) digital QSO's.
73 - Skip KH6TY
Trevor . wrote:
Regarding Spread Spectrum Notice of Proposed Rule Making (NPRM)
http://www.arrl.org/news/stories/2010/03/18/11396/?nc=1
<http://www.arrl.org/news/stories/2010/03/18/11396/?nc=1>
It proposes to reduce some of the restrictions on Spread Spectrum but
unfortunately does nothing about permitting the use at HF and VHF of
SS modes that completely fit within the bandwidth of a phone signal
(say 3 kHz on HF and 15 kHz on VHF).
It says comments can be filed on or before 30 days after date of
publication in the Federal Register. Instructions on how to file
comments on the NPRM only are listed on pages 6-7 in the NPRM.
http://hraunfoss.fcc.gov/edocs_public/attachmatch/FCC-10-38A1.pdf
<http://hraunfoss.fcc.gov/edocs_public/attachmatch/FCC-10-38A1.pdf>
Electronic Comment Filing System
http://www.fcc.gov/cgb/ecfs/ <http://www.fcc.gov/cgb/ecfs/>
73 Trevor M5AKA
