Please allow my 2 cents worth. KN6KB in his presentation of SCAMP to the DCC a couple of years had a slide that showed where he measured P III with a channel simulator from KC7WW. I showed that around -5 dB SNR there was still something in the area of 200 WPM throughput.
I believe that you might be able to see some incidental throughput perhaps at less than 50 WPM. The thing that will absolutely kill Pactor III is its 100 baud physical signaling rate. There are conditions on HF when this high of a baud rate simply will NOT propagate. IMHO, if they were to drop the baud rate to 50, they might even see a higher throughput at a -5 dB SNR. Its interesting to note that KC7WW measured MT63 on his channel simulator and MT63 showed 200 WPM at or near -5 dB SNR. I discussed this at leangth with Vic Poor when we had breakfast at the DCC and he agreed that the above was probably true for Pactor III and MT63-2K between -2 and -7 dB. If anyone would like to verify KN6KB's measurements, I recommend you purchase a copy of the DCC proceedings from TAPR that contain KN6KB's SCAMP presentation...or purchase a KC7WW channel simulator and check it yourself. Note, you might also try duplicating the test using Moe Wheatly's PathSimulator. It runs on a PC and is free to download. 73, Walt/K5YFW -----Original Message----- From: digitalradio@yahoogroups.com [mailto:[EMAIL PROTECTED] Behalf Of KV9U Sent: Wednesday, January 10, 2007 3:12 PM To: digitalradio@yahoogroups.com Subject: Re: [digitalradio] Pactor versus Olivia Rich and group, I have read from the SCS website that there is still throughput with P2 and especially P3 when down to maybe as low as -16 db below noise. Others have claimed that Pactor 2 and 3 drastically drop off by the time you reach -5 db S/N such as KN6KB's RFfootprints powerpoint on comparing various digital modes. Can you quantify what some throughputs might be at the low S/N ratios? There isn't any miracle modulation scheme with pactor 2 and 3 from what I can see. What they do is optimize many little things which gives them improved throughput. I question whether P3 is going to work a lot better than the wider Olivia under the most difficult conditions, although I hear the claim made that it does extremely well. But I am not sure of the actual throughput under real world conditions. The curious thing is that if it can not operate below 100 baud, there should be times of doppler, bit smearing, multipath, etc., that would make pactor modes completely unusable even though low baud rate modes would work quite well. 73, Rick, KV9U Rich Mulvey wrote: >What BW/tones were you using for the Olivia comparison? > >The thing about Pactor 1 is that it's adequate for relatively good >conditions, but is noticably worse than >Pactor 2 and 3 when things get marginal. Pactor 3 absolutely shines >under the absolute worst conditions, >when all of the sound card mode operators have given up and turned off >their rigs, complaining that the band >is dead. ;-) > >- Rich > > > > > Announce your digital presence via our DX Cluster telnet://cluster.dynalias.org Our other groups: http://groups.yahoo.com/group/dxlist/ http://groups.yahoo.com/group/themixwgroup http://groups.yahoo.com/group/contesting http://groups.yahoo.com/group/wnyar http://groups.yahoo.com/group/Omnibus97 Yahoo! Groups Links
