On 7/20/2010 3:54 PM, KH6TY wrote:
>Our on-air tests show that ROS 16 baud, 2200 Hz wide spread spectrum
was very poor on UHF under Doppler >spreading. Can you confirm this with
flutter tests like Jaak has done.
Skip,
My path tests show that ROS is less tolerant to Doppler spread than
Olivia or one of it's variants so I'd have to agree with your on-air
evaluation. Throughput starts to fail as the Doppler spread is increased
beyond 20Hz (two channels 2ms delay) and I suspect you could be
experiencing frequency dispersions beyond that range.
I haven't been able to find any propagation data that shows how much
Doppler spread is likely take place on VHF/UHF. Wish I knew that answer
to that.
Tony -K2MO
Tony,
Our on-air tests show that ROS 16 baud, 2200 Hz wide spread spectrum
was very poor on UHF under Doppler spreading. Can you confirm this
with flutter tests like Jaak has done on
http://contestia.blogspot.com/p/pathsim_09.html
<http://contestia.blogspot.com/p/pathsim_09.html> ?
73, Skip KH6TY
On 7/19/2010 9:42 PM, Tony wrote:
All,
With all the attention ROS has been getting lately, I thought it
would be interesting to see how the narrow mode compared to the wide
version under the controlled environment of the HF path simulator.
After a few hours of testing, it seems there's little difference
between the two.
The simulator indicated that they both had the same sensitivity
(-15db) and essentially the same poor channel performance
characteristics (see throughput samples below). In no case did one
mode outperform the other to the point where it would make any real
difference; both have the essentially the same wpm rate as well.
These tests are not conclusive, but they do suggest that there may
not be any real advantage in using the wide mode vs narrow under most
circumstances. Of course, the simulator can only emulate the basic
characteristics of the real HF channel so it would be interesting to
hear from those who have compared the two on-air.
Tony -K2MO
____________________________________________________________
CCIR-520-2 POOR CHANNEL SIMULATIONS: -11DB SNR
ROS 2250 / 16 baud
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ROS 500 / 16 baud
the quick brown fox jumps over the lazy dog
the quick brown fox jumps over the lazy dog
the quick breFn fox juo3s over tes lazy dog
the quæe t ´uls r?umps over the lazy dog
the quick brown fox jumps over the lazy dog
the quick brown f Á jumps over the lazy dog
the quick brown fox jumps over the lazy dogQo
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