> > Very important information, Rein, and thank you for sharing it with the > group. This is the kind of real world information we need to hear. > Considering the enormous amount of bandwidth MT-63 takes up, it would > have to work several times faster and better than a narrow band mode to > warrant such BW useage. > > I suppose a mode like MFSK16 would be very difficult to tune in, but if > we could have a similar mode that operated several times faster with say > no more than 1 KHz BW, would this be a possible contender for a robust > waveform when compared to PSK63?
Possibly... But look at the facts: PSK63 bandwidth 100 Hz, MFSK16 250 Hz PSKmail sync range 20 Hz MFSK16 5 Hz PSKmail throughput 67 wpm MFSK16 42 wpm (30 WPM with arq and 64byte blocks). The sync range is important, as the server is on a fixed frequency (nobody to point-and-click here). AFC range on the server is limited to +- 15 Hz, and sync will be quick if the client is within 10 Hz of the center frequency. If you would quadruple the bandwidth of MFSK16 by using a Baud rate 4x as high you would get: MFSK16 Bandwidth 1000 Hz MFSK sync range 20 Hz MFSK Throughput (without arq overhead) 170 wpm (150 wpm with arq and 64 byte data blocks) This is not too far from the MT63 throughput of 200 wpm without arq, in half the bandwidth. But I am not sure the 4x symbol rate would still be as robust as that of MT63, and whether the error rate improvement compared to PSK63 would be large enough to warrant a bandwidth of 10x that of PSK63 is questionable. Still, if it were available I would like to try it, as it may be better in certain forms of QSB. The QSB we encounter on the path between Benicassim(Spain) and Stockholm(Sweden) is often so severe that the signal is gone completely for several (sometimes 10) seconds, especially during the times propagation switches between 1F and 2F mode, and they appear simultaneously. The only solution is then to 'work around the holes', like you would do when driving on a Montenegran road. Also, the better error rate may result in less repeated blocks, the only quality ctiterion for a PSKmail channel. I have tried MFSK16 for PSKmail also. We are using stable equipment for PSKmail (FT897D), so 5 Hz is just about within the range of possibilities of the rig. But improvement with respect to PSK63 was marginal, the throughput only half the speed and the bandwidth 2.5x Moreover I had to increase power to get those improvements (small wonder, the power is in a larger bandwidth). Until I have tried it I will remain sceptical. The 63 Hz Baudrate of PSK63 is pretty well ideal for most circumstances at HF. Looks like Skip Teller did a good job when he made PSK63... 73, Rein PA0R PS: You may want to look at an example of what PSK63-ARQ can do under marginal circumstances at http://pskmail.wikispaces.com/PSK_arq Path length to qso partner as well as the server was about 1000 Miles. -- http://pa0r.blogspirit.com Need a Digital mode QSO? Connect to Telnet://cluster.dynalias.org Other areas of interest: The MixW Reflector : http://groups.yahoo.com/group/themixwgroup/ DigiPol: http://groups.yahoo.com/group/Digipol (band plan policy discussion) 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: mailto:[EMAIL PROTECTED] mailto:[EMAIL PROTECTED] <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
