Thanks for the testing Tony. We observe Doppler shifts of as much as 100 Hz and Doppler spreads around 50 Hz or greater. On SSB phone, a S3 signal will not be intelligible and you can hear the voice pitch go down in a fluttering manner. ROS definitely produces nothing but garbage when SSB phone is not understandable, but Contestia will keep on printing perfectly.
That is just one more reason that there are better modes than ROS we can use, are of much less bandwidth, and equal of better sensitivity. As someone pointed out, spread spectrum is basically used for encryption and has no advantage in disturbed environments. BTW, it is interesting to note the huge impact of Pawel Jalocha has on the use of digital on the ham bands. His SLOPSK development was the basis for G3PLX's PSK31, and now, Olivia is the highest performing digital mode. It is as if he were the "father" of all we are working with today! I wish I knew more about his background. 73, Skip KH6TY On 7/21/2010 12:15 AM, Tony wrote: > > > 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 >>> the quick brown fox jumps over the lazy dog >>> the quick brown fox jumps over the lazlµog >>> Lghe quick brown fox jumps over the lazy dog >>> the quccirown fox jumps over the lazy dog >>> the quick brown fox jumps over the lazy dog >>> Âe quick brown fox jumps over the lazy dog >>> the quick brown fealoeumps ovahe lazEh/i >>> >>> 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 >>> >> >> >> __________ Information from ESET NOD32 Antivirus, version of virus >> signature database 5293 (20100719) __________ >> >> The message was checked by ESET NOD32 Antivirus. >> >> http://www.eset.com <http://www.eset.com> > > > ------------------------------------ http://www.obriensweb.com/digispotter.html Chat, Skeds, and "Spots" all in one (resize to suit) Facebook= http://www.facebook.com/pages/digitalradio/123270301037522 Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/digitalradio/ <*> Your email settings: Individual Email | Traditional <*> To change settings online go to: http://groups.yahoo.com/group/digitalradio/join (Yahoo! ID required) <*> To change settings via email: digitalradio-dig...@yahoogroups.com digitalradio-fullfeatu...@yahoogroups.com <*> To unsubscribe from this group, send an email to: digitalradio-unsubscr...@yahoogroups.com <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
