Hi Mark, As one of the very earliest testers of Olivia, I got to try out the mode under varying conditions. I did not take notes of the specific combinations that we used, but I am sure that we used too high a baud rate on 80 meters. If you want to maintain or increase the CPS rate you have no choice.
But we wanted to see how far we could go before it failed. And we certainly did not want to accept any slower speed than the default speed which is slower than MFSK16 and that is plenty slow. There are only a few combinations of bandwidth and tones that will give you an adequate character per second speed. The default 32 tones with 1000 BW at 31.25 is only 2.5 CPS. Not really fast enough for many of us but some might find it OK. MFSK16 is not a speed demon either and runs at something around 3.5 CPS which I consider the benchmark to beat. If you tried to use Olivia at 250 Hz what kind of character speed would you get? None are useable from what I have determined. In fact, I made up a chart to reflect the practical number tones to BW and there aren't that many. When you try to go faster than the default, to a more realistic speed, say 4 to 5 CPS, you have to accept the wide BW operation of Olivia. Isn't it correct that even at 500 Hz you would only be able to use 2 tones and still only have a 3.3 CPS rate? How robust would this be? Has it been your experience that it can compare to MFSK16? Even though you are going to be wider than MFSK16? If the speed is only 1 CPS, then I really don't consider that to be all that useful for keyboarding. Maybe for some specialized purpose? When you factor in the minimum acceptable keyboard speed, with a modest footprint, and ability to handle difficult conditions, MFSK16 seems to be hard to beat. 73, Rick, KV9U -----Original Message----- From: Mark Miller [mailto:[EMAIL PROTECTED] Sent: Monday, April 04, 2005 4:19 PM To: [email protected] Subject: RE: [digitalradio] PSK10 or MFSK16 Rick, Yes I probably did read more into that. Thanks for clarifying. Your comments are interesting. At 02:47 PM 4/4/2005, you wrote: >when we have used it on really high QRN nightime 80 >meters, for example, it would do OK with the wide BW and slow data rate. But >when you try some of the lower number of tones (narrower BW) it could not >perform. Even if it was still way wider than MFSK16. Then when we switched >back to using MFSK16 the signal worked very well. Olivia is more bandwidth efficient for the same baud rate and bits per second with respect to MFSK16 (250 Hz vs. 384 Hz). The control that you have with Oliva is the number of tones and the bandwidth. The number of tones does not affect the bandwidth. The bandwidth/number of tones determines the baud rate. Olivia uses 64 bit blocks so the seconds per block is 64/baud. The number of tones determines the bits per symbol so the character speed is seconds per block/bits per symbol. The interleaving depth is determined by the number of tones. By lowering the number of tones in your example above you were not affecting the bandwidth, you were increasing the baud rate, reducing the interleaving depth and at the same time decreasing the characters per second. I am not surprised that performance degraded. Perhaps what you meant to say was that you decreased the number of tones and decreased the bandwidth. In that case you could keep the baud rate the same and keep the characters per second about the same. The penalty is reduced interleaving which will degrade performance. But I don't think that is what you did because you mentioned a decrease in "data rate" which I am interpreting as character speed. MFSK16 has 16 tones and a bandwidth of 384 Hz. The baud rate is 16 and the data rate is 62.5 bits per second. To nearly equal those parameters with Olivia you would choose 16 tones and 250 bandwidth. Olivia is more bandwidth efficient for the same baud rate and bits per second. The character speed will be slower at 1 character per second, but the performance should be better because of the more robust FEC. The same thing happens with QPSK31 vs. BPSK31 and PSK31FEC vs. PSK31. The penalty for increased robustness and unchanged bandwidth is slower character speed. 73, Mark N5RFX The K3UK DIGITAL MODES SPOTTING CLUSTER AT telnet://208.15.25.196/ Yahoo! Groups Links -- No virus found in this incoming message. Checked by AVG Anti-Virus. Version: 7.0.308 / Virus Database: 266.9.1 - Release Date: 4/1/2005 -- No virus found in this outgoing message. Checked by AVG Anti-Virus. Version: 7.0.308 / Virus Database: 266.9.1 - Release Date: 4/1/2005 The K3UK DIGITAL MODES SPOTTING CLUSTER AT telnet://208.15.25.196/ Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/digitalradio/ <*> 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/
