Re: [digitalradio] Re: Sub Channel DQPSK
Well, I do not have a distinct characterization of Olivia submodes. 8/500 seems to be fair enough, not too greedy on bandwidth and works where other modes (not Olivia) fail. I have used the most common available on MultiPSK, that is, 8/250, 8/500, and 16/500. Ocassionally, 32/1000, or even 2/125 on a couple of QSO's using MixW. I felt 2/125 a bit better than RTTY, but made no serious comparisons, and I feel (maybe a bit of a gut feeling) that Olivia with just two tones defeats most of its adventages. 73, Jose, CO2JA --- Rick wrote: > Have you found particular combinations of Olivia BW and tones that seem > to work the best for various conditions? > > My frustration with Olivia is that it is impractically slow for keyboard > chats unless you use the higher baud speeds to get the wpm to at least > 30 wpm. But then it does not seem to work as well. > > But if the choice was some communication instead of no communication, > there would be times that it would be a good choice. My main interest is > in using sound card modes that work well for emergency communication > with lower power and lesser quality antennas, particularly on HF NVIS. > > 73, > > Rick, KV9U > > Jose Amador wrote: >> As all differentially encoded modulations, it has a price, in the form >> of burst errors following a wrong bit. >> >> For me, Olivia is far better than any Domino EX modes, including Domino >> with FEC.With FEC it is more robust, >> but becomes slower than Olivia, without reaching the same degree of >> robustness. It is my impression with actual >> tests on the air. > __ Participe en Universidad 2008. 11 al 15 de febrero del 2008. Palacio de las Convenciones, Ciudad de la Habana, Cuba http://www.universidad2008.cu
Re: [digitalradio] Re: Sub Channel DQPSK
Have you found particular combinations of Olivia BW and tones that seem to work the best for various conditions? My frustration with Olivia is that it is impractically slow for keyboard chats unless you use the higher baud speeds to get the wpm to at least 30 wpm. But then it does not seem to work as well. But if the choice was some communication instead of no communication, there would be times that it would be a good choice. My main interest is in using sound card modes that work well for emergency communication with lower power and lesser quality antennas, particularly on HF NVIS. 73, Rick, KV9U Jose Amador wrote: > > As all differentially encoded modulations, it has a price, in the form > of burst errors following a wrong bit. > > For me, Olivia is far better than any Domino EX modes, including Domino > with FEC.With FEC it is more robust, > but becomes slower than Olivia, without reaching the same degree of > robustness. It is my impression with actual > tests on the air. > > >
Re: [digitalradio] Re: Sub Channel DQPSK
Vojtech Bubnik escribió: > PSK as well as MFSK will be affected by multipath, it will create > another type of inter symbol interference - time overlap. DominoEX > with its incremental MFSK tries to cope with it, but there is a price > for that. I am not convinced yet that the incremental MFSK is the > best thing. As all differentially encoded modulations, it has a price, in the form of burst errors following a wrong bit. For me, Olivia is far better than any Domino EX modes, including Domino with FEC.With FEC it is more robust, but becomes slower than Olivia, without reaching the same degree of robustness. It is my impression with actual tests on the air. Jose, CO2JA __ Participe en Universidad 2008. 11 al 15 de febrero del 2008. Palacio de las Convenciones, Ciudad de la Habana, Cuba http://www.universidad2008.cu
[digitalradio] Re: Sub Channel DQPSK
> Would the phase distortion that can corrupt a PSK signal occur the same on a > M-PSK signal? Phase and frequency modulation are two sides of the same coin. There is a baseband transformation to translate from phase to frequency modulation and vice versa - integration / derivation. Integrate baseband signal for phase modulator to get baseband for frequency modulator, derive baseband signal for frequency modulator to get baseband signal for phase modulator. The same phase distortion rendering PSK signal unreadable shows as a Doppler shift making the signal leaking into a neighbor frequency bins. Generally, there will be some inter symbol interference, but MFSK will still work, if the bins are not too narrow. PSK as well as MFSK will be affected by multipath, it will create another type of inter symbol interference - time overlap. DominoEX with its incremental MFSK tries to cope with it, but there is a price for that. I am not convinced yet that the incremental MFSK is the best thing. > If the phase distortion affects all the sub channels then doing differential > PSK among the sub channels would work where symbol to symbol DxPSK would not > work. It is rather not the case. Polar flutter is frequency dependent. It seems you are jumping on the train very fast. I hope you will help me to make PocketDigi better, because my time for PocketDigi will be shortened as I am slowly getting busy with the Father project, hi. 73, Vojtech OK1IAK
