I'll leave the solution to those much more knowledgeable than I am, but
my simplistic guess is perhaps ROS does not have the degree of
redundancy that Olivia has, and when enough tones are distorted, the
data is lost. I think the main point is that Olivia outperforms ROS in
less than half the bandwidth. What we hoped to find is ROS exceeding
Olivia under the same conditions, but unfortunately, it is far away from
even the same performance under those conditions. Using a wider
spreading is not practical, because the IF bandpass of almost all
transceivers in use is only around 2500 Hz. It would take SDR's on both
ends to use a wider spreading, and it will probably be many years before
those are commonplace.
Presumably, a wider spread can be combined with using more carriers and
still maintain a good S/N, but using a wider spread is just not
practical at this point in time. Maybe FHSS alone is just not the way to
go, considering all the adverse conditions we have to work under, which
includes the need for a reasonable typing speed.
It's too bad the code is being kept a secret, or others may be able to
contribute to improving the performance.
73 - Skip KH6TY
w2xj wrote:
Yes but at UHF there seems to not be enough spread to tolerate the
Doppler shift. If the frequencies were further apart, and were received
through a wider window, the Doppler would be tolerated better but at
what penalty in noise? I can think of a few ways to solve your problem
but not with existing sound card modes.
