Re: [digitalradio] ROS on UHF]]
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.
Re: [digitalradio] ROS on UHF]]
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. KH6TY wrote: > Based on observations of the tones on the waterfall on the air, > compared to observing them locally, and hearing the raucous tones > compared to bell-like quality locally, my guess is that perhaps the > modulation is disturbed or the tones moved in frequency far enough so > there is no decoding. If we try to use DominoEx, which is very > tolerant to drift, the Doppler distortion also stops DominoEx from > decoding. MFSK16 is not usable, because the Doppler shift is so great > that tuning is lost and the AFC cannot follow it. It is not unusual to > see a slow Doppler shift of 50 Hz to 100 Hz on 70cm, but the most > severe problem is a fast Doppler distortion which is present almost > all the time and destroys the integrity of the carriers, at least as > it is possible to hear and see on the waterfall. > > I can't compare ROS on HF to UHF, except for monitoring, as it is > illegal to transmit on HF, but monitoring on HF does not show the same > problems. I have seen ROS signals start printing garbage on HF in a > QSB fade and then recover when the fade ends, but there is no > published specification for the minimum S/N that the 16 baud variation > is supposed to work at. Even when there is no QRM, I have seen > decoding of ROS 16 baud, 2250 Hz width, stop at metrics of -8 dB. If > this corresponds to S/N, then the 16 baud version does not compare > favorably with Olivia or MFSK16, which can work 4 dB to 5 dB lower. > > My guess is that the problem is not because the spreading in ROS is > too little, but on UHF, that the tones themselves are disturbed in a > way that makes ROS just print garbage when Olivia is still printing > quite well. ROS stopped decoding today even when SSB phone was about > Q4 copy, and under those conditions Olivia prints without any errors. > > Unfortunately the way it is now, we are unable to successfully use ROS > on UHF, for whatever the reason, and it is illegal to use it on HF > under FCC jurisdiction. > > That is too bad, because ROS is definitely fun to use. > > 73 - Skip KH6TY > > > > > w2xj wrote: >> >> >> >> If there were documentation on ROS then there would the possibility of >> >> investigating the problem further and maybe adding improvements. Part of >> the problem is that even if there is a large degree of spreading >> compared to the data rate, the channel is still quite narrow and a large >> portion of it subject to the same disturbances or interference. This is >> similar to what happens with the various commercial broadcast digital >> systems. The wider ones are much more robust, especially in regard to >> multipath, even though the data payload was increased in proportion. >> >> KH6TY wrote: >> > > Simon HB9DRV wrote: There's a lot more to Olivia than being >> > multi-tone MFSK. >> >> >> >> >> >> >> >> >> > I am aware of that, Simon. >> > >> > However, Olivia is currently the most popular digital mode other than >> > PSK31 and RTTY, and the question was if ROS 16 baud was worth using >> > twice the bandwidth of Olivia. We hoped that it would be, because on >> > UHF, space is not at a premium as it is on HF, but ROS 16 baud, (the >> > spread spectrum variation) at 2250 Hz width, was not even as good as >> > SSB phone under the fast Doppler flutter conditions. So, as a choice >> > of modes currently available, either MFSK16 (my personal preference on >> > HF, but impractical on UHF due to the necessity to tune so accurately >> > and have little or no drift) or Olivia, is a far better choice than >> > ROS, and performs better. >> > >> > We would like nothing better if there were a mode that outperformed >> > Olivia at equivalent typing speed, and could copy further into the >> > noise than Olivia can, and is more tolerant to mis-tuning or drift >> > than MFSK16, but so far ROS is not the one. As things stand, CW >> > (decoded by ear) is currently the "last mode standing", but it seems >> > it must be possible to come up a mode that can beat CW under the >> > typical conditions found on UHF. >> > >> > 73 - Skip KH6TY >> > >> > >> >> >> >> >> > >> >> >
Re: [digitalradio] ROS on UHF]
Based on observations of the tones on the waterfall on the air, compared to observing them locally, and hearing the raucous tones compared to bell-like quality locally, my guess is that perhaps the modulation is disturbed or the tones moved in frequency far enough so there is no decoding. If we try to use DominoEx, which is very tolerant to drift, the Doppler distortion also stops DominoEx from decoding. MFSK16 is not usable, because the Doppler shift is so great that tuning is lost and the AFC cannot follow it. It is not unusual to see a slow Doppler shift of 50 Hz to 100 Hz on 70cm, but the most severe problem is a fast Doppler distortion which is present almost all the time and destroys the integrity of the carriers, at least as it is possible to hear and see on the waterfall. I can't compare ROS on HF to UHF, except for monitoring, as it is illegal to transmit on HF, but monitoring on HF does not show the same problems. I have seen ROS signals start printing garbage on HF in a QSB fade and then recover when the fade ends, but there is no published specification for the minimum S/N that the 16 baud variation is supposed to work at. Even when there is no QRM, I have seen decoding of ROS 16 baud, 2250 Hz width, stop at metrics of -8 dB. If this corresponds to S/N, then the 16 baud version does not compare favorably with Olivia or MFSK16, which can work 4 dB to 5 dB lower. My guess is that the problem is not because the spreading in ROS is too little, but on UHF, that the tones themselves are disturbed in a way that makes ROS just print garbage when Olivia is still printing quite well. ROS stopped decoding today even when SSB phone was about Q4 copy, and under those conditions Olivia prints without any errors. Unfortunately the way it is now, we are unable to successfully use ROS on UHF, for whatever the reason, and it is illegal to use it on HF under FCC jurisdiction. That is too bad, because ROS is definitely fun to use. 73 - Skip KH6TY w2xj wrote: If there were documentation on ROS then there would the possibility of investigating the problem further and maybe adding improvements. Part of the problem is that even if there is a large degree of spreading compared to the data rate, the channel is still quite narrow and a large portion of it subject to the same disturbances or interference. This is similar to what happens with the various commercial broadcast digital systems. The wider ones are much more robust, especially in regard to multipath, even though the data payload was increased in proportion. KH6TY wrote: > > Simon HB9DRV wrote: There's a lot more to Olivia than being > multi-tone MFSK. >> >> >> >> > I am aware of that, Simon. > > However, Olivia is currently the most popular digital mode other than > PSK31 and RTTY, and the question was if ROS 16 baud was worth using > twice the bandwidth of Olivia. We hoped that it would be, because on > UHF, space is not at a premium as it is on HF, but ROS 16 baud, (the > spread spectrum variation) at 2250 Hz width, was not even as good as > SSB phone under the fast Doppler flutter conditions. So, as a choice > of modes currently available, either MFSK16 (my personal preference on > HF, but impractical on UHF due to the necessity to tune so accurately > and have little or no drift) or Olivia, is a far better choice than > ROS, and performs better. > > We would like nothing better if there were a mode that outperformed > Olivia at equivalent typing speed, and could copy further into the > noise than Olivia can, and is more tolerant to mis-tuning or drift > than MFSK16, but so far ROS is not the one. As things stand, CW > (decoded by ear) is currently the "last mode standing", but it seems > it must be possible to come up a mode that can beat CW under the > typical conditions found on UHF. > > 73 - Skip KH6TY > > >> >> >
Re: [digitalradio] ROS on UHF]
If there were documentation on ROS then there would the possibility of investigating the problem further and maybe adding improvements. Part of the problem is that even if there is a large degree of spreading compared to the data rate, the channel is still quite narrow and a large portion of it subject to the same disturbances or interference. This is similar to what happens with the various commercial broadcast digital systems. The wider ones are much more robust, especially in regard to multipath, even though the data payload was increased in proportion. KH6TY wrote: > > Simon HB9DRV wrote: There's a lot more to Olivia than being > multi-tone MFSK. >> >> >> >> > I am aware of that, Simon. > > However, Olivia is currently the most popular digital mode other than > PSK31 and RTTY, and the question was if ROS 16 baud was worth using > twice the bandwidth of Olivia. We hoped that it would be, because on > UHF, space is not at a premium as it is on HF, but ROS 16 baud, (the > spread spectrum variation) at 2250 Hz width, was not even as good as > SSB phone under the fast Doppler flutter conditions. So, as a choice > of modes currently available, either MFSK16 (my personal preference on > HF, but impractical on UHF due to the necessity to tune so accurately > and have little or no drift) or Olivia, is a far better choice than > ROS, and performs better. > > We would like nothing better if there were a mode that outperformed > Olivia at equivalent typing speed, and could copy further into the > noise than Olivia can, and is more tolerant to mis-tuning or drift > than MFSK16, but so far ROS is not the one. As things stand, CW > (decoded by ear) is currently the "last mode standing", but it seems > it must be possible to come up a mode that can beat CW under the > typical conditions found on UHF. > > 73 - Skip KH6TY > > >> >> >
Re: [digitalradio] ROS on UHF
> Simon HB9DRV wrote: There's a lot more to Olivia than being multi-tone MFSK. I am aware of that, Simon. However, Olivia is currently the most popular digital mode other than PSK31 and RTTY, and the question was if ROS 16 baud was worth using twice the bandwidth of Olivia. We hoped that it would be, because on UHF, space is not at a premium as it is on HF, but ROS 16 baud, (the spread spectrum variation) at 2250 Hz width, was not even as good as SSB phone under the fast Doppler flutter conditions. So, as a choice of modes currently available, either MFSK16 (my personal preference on HF, but impractical on UHF due to the necessity to tune so accurately and have little or no drift) or Olivia, is a far better choice than ROS, and performs better. We would like nothing better if there were a mode that outperformed Olivia at equivalent typing speed, and could copy further into the noise than Olivia can, and is more tolerant to mis-tuning or drift than MFSK16, but so far ROS is not the one. As things stand, CW (decoded by ear) is currently the "last mode standing", but it seems it must be possible to come up a mode that can beat CW under the typical conditions found on UHF. 73 - Skip KH6TY
RE: [digitalradio] ROS on UHF
There's a lot more to Olivia than being multi-tone MFSK. A fairer comparison with a new mode such as ROS would be MFSK as the features of Olivia that make it so very robust could (should) be added at a later date. To put it simply Olivia hunts for the best signal it can decode and has error correction, this 'hunting' is a reason for the greater CPU usage. Simon Brown, HB9DRV http://sdr-radio.com From: digitalradio@yahoogroups.com [mailto:digitalra...@yahoogroups.com] On Behalf Of hteller Sent: 21 March 2010 15:38 To: digitalradio@yahoogroups.com Subject: [digitalradio] ROS on UHF ... whereas Olivia is a multitone FSK mode and does very well.
