[digitalradio] ROS on UHF
Extensive testing of ROS on the air on UHF have now been concluded. Unfortunately, ROS totally fails for UHF communications, in either 16 baud, or 1 baud variants, and using either the HF or EME channel. Even with ROS metric readings between -1 dB and -8 dB (i.e. relatively strong signals), ROS only printed on 16 baud or on 1 baud as long as the tones sounded pure in the headphones, but as soon as the tones sounded wobbly and became broadened on the waterfall, decoding became total garbage. When SSB phone was understandable (but with significant flutter), ROS still would not print, even after a successful Frame Acquisition and Symbol Synchronization and print of the callsigns. We switched to Olivia 32-1000 and print was perfect, as expected, as signals were strong, even though QSB and flutter could be heard. The problem is that ROS is apparently completely destroyed by what is appears to be Doppler flutter (for want of a better term), which is present on UHF most of the time. Under those conditions, the spread spectrum technique used in ROS 16 baud and ROS 1 baud modes simply does not survive the Doppler disturbances, whereas Olivia is a multitone FSK mode and does very well. The ROS 500 Hz FSK variants were not tested, as the hope was that the spread spectrum variant of ROS would outperform Olivia, but instead it did much worse. Olivia 16-500, as a reference, almost equals CW in ability to work near the noise, so we were hoping that ROS would work under the noise, but it did not. Apparently, spread spectrum is just a poor choice whenever there is Doppler-induced distortion like there usually is on 70cm. When I use two transceivers and computers locally, where there are no Doppler effects, all the ROS variants work perfectly, but in real life conditions, where we are faced with QRM, QSB, multipath, and unstable atmospheric moisture conditions that cause fast frequency shifts (apparently Doppler-induced disturbances), ROS fails completely. As Olivia has been designed to accommodate all the difficult conditions we have to deal with on both HF and above, Olivia is a much better choice, and at half the bandwidth, at the same typing speed. This concludes our tests with ROS and there will be further testing or use of ROS by this station. ROS spread spectrum is legal to use in the US above 222 MHz, so if anyone else can make such tests, please post the results here. 73 - Skip KH6TY digitalradio@yahoogroups.com wrote: There are 7 messages in this issue. Topics in this digest: 1a. Re: Scanning PSKmail WARC freqs From: Rein Couperus 2. space to ground audio channels via SDR From: Andy obrien 3a. Has anyone tried the WINMOR keyboarding? From: Howard Z 3b. Re: Has anyone tried the WINMOR keyboarding? From: Andy obrien 4a. Net14 + PK-63 From: G0JXN Jim 4b. Re: Net14 + PK-63 From: Andy obrien 4c. Re: Net14 + PK-63 From: Andy obrien Messages 1a. Re: Scanning PSKmail WARC freqs Posted by: Rein Couperus r...@couperus.com pa0r Date: Sat Mar 20, 2010 2:09 am ((PDT)) The PSkmail servers only use CALL de CALL when confirming messages or user beaons... If you have captured PSK250 then it will probably have been US servers, or Intermar maritime servers on 10148.0 (center freq) (DK4XI-30), as on 10147.0 we use PSK500R as default. As soon as a connection is established, RSID is only used for the mode change protocol, and a lot of users don't use the software supporting the new protocol yet... Rein PA0R Rein et al. I scanned 10147 and 18105 today for six hours, alternating every 90 seconds with a 3 Khz range. I only picked up three PSk250 RS IDs on 30M and NONE on 17M. Each RS ID on 30M was not decoded well enough to produce a callsign. Since Muktipsk looks for a de ** string, perhaps the stations were sending PSKMAIL IDs without a de ? For the last hour , I listening for 30 minutes on each frequency, listened with my own ears. I heard no PSK250 on 18105 . On 30M I heard two RS IDs and several PSK250 signals without RS ID. perhaps not all PSK mail servers are using RS ID yet ? Andy K3UK Messages in this topic (3) 2. space to ground audio channels via SDR Posted by: Andy obrien k3uka...@gmail.com obrienaj Date: Sat Mar 20, 2010 1:05 pm ((PDT)) While not exactly digital modes... -- Forwarded message -- From: pauljmarsh pauljma...@yahoo.co.uk Date: Sat, Mar 20, 2010 at 3:07 PM Subject: [SDR-IQ] Re: Impressions on SDR-IP To: sdr...@yahoogroups.com Some impressions of the IP is at http://www.pudxk.blogspot.com/73,Tarmo... Hi Tarmo,all, Thats a very interesting write up. I've put my observations on
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.
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]
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]]
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
