Re: [digitalradio] MFSK16 tuning improvement, was:best mode to use for weak signal HF work and othe
Hello Vojtech, It works on Olivia because this mode uses a transform (Walsh Hadamard), an interleaving and a pseudo-random function: so within a pack of bits defined in time and in frequency there is a very strong correlation and outside the correlation decreases rapidly. This permits to define the best band of frequencies (maximum correlation). This does not exist in MFSK16 where a convolution code is used (so there is no such correlation). Moreover, the S/N measure is too much imprecise, the selection would be almost random on weak signals. If you use RS ID (RX and TX), the tuning is automatic. 73 Patrick - Original Message - From: Vojtech Bubnik To: digitalradio@yahoogroups.com Sent: Wednesday, December 27, 2006 4:57 PM Subject: [digitalradio] MFSK16 tuning improvement, was:best mode to use for weak signal HF work and othe Hi Patrick. I wonder whether it would make sense to improve MFSK16 to be more easy to use. The idea is to decode multiple streams in parallel as it is done in Olivia and pick the one with the best S/N. It seems to me that Olivia is only that much popular because it is a lot easier to tune than MFSK16. 73 and GL, Vojtech OK1IAK --- In digitalradio@yahoogroups.com, "Patrick Lindecker" <[EMAIL PROTECTED]> wrote: > > Hello Rick, > > >If often wonder if a mode that has a very wide ability to print even if > >not tuned in well has to have some tradeoffs in robustness compared with > >critical to tune modes. Anyone have specific information about that? > The ability of DominoEx to be tuned very easily is that the modulation is an IFK one and not a MFSK one. It means that you measure a difference of frequency not a frequency in absolute as in MFSK. The good point it is easy to tune (no absolute reference of frequency) but the bad point is that when you do an error, the second symbol is also in error...you double the error (it's a bit like in PSK31, which one measures a difference of phase: if you do a error on one symbol, the next symbol will be also in error). > > >Can anyone say with some degree of certainly what modes you think will > >get through on the low bands with high QRN levels? > I think Olivia must be good but Contestia is more close to ideal as twice quicker than Olivia with a minimum S/N just 1 or 1.5 dB superior to Olivia. > > 73 > Patrick > > > > - Original Message - > From: KV9U > To: digitalradio@yahoogroups.com > Sent: Friday, December 01, 2006 7:49 PM > Subject: Re: [digitalradio] best mode to use for weak signal HF work and other mode discussions > > > Brett, > > There are several sound card modes commonly used in addition to the most > popular PSK31 and 45 baud RTTY That would be MFSK16, Olivia, Hell, and > Throb/ThrobX. Although there are others, I rarely, if ever hear them. I > no longer seem to hear any MT-63 and the CHIP modes came and went quickly. > > I wanted to do more experimenting with DominoEX and last night I got to > work some 160 meter NVIS. We started out on MFSK16 but I have been > having a lot of problems with this mode as of late and maybe it is > because my soundcard is not calibrated correctly, but I find that I have > to use about 10 to 20 Hz offset RIT in order to print the other station. > MFSK16 really does require extremely accurate tuning of perhaps 4 Hz or > so. My rig is an ICOM 756 Pro 2 which is supposed to have very good > stability at 0.5 ppm. > > The other station and I tried some PSK31 for a short time when I lost > him on MFSK16 and was just able to get him to try DominoEX at 11 baud. > His signal was close to the noise although it was not that noisy on 160 > since we are in the winter season. The print was very poor at 11 baud, > so we dropped to 8 baud and things got better. Even at 8 baud, the speed > of transmission is still faster than MFSK16. We had a CW station come up > about 50 Hz below us and when that station was transmitting, it > drastically affected the print of the DEX mode, even at 8 wpm. The one > thing that DEX has going for it is that it is less critical to tune in. > > If often wonder if a mode that has a very wide ability to print even if > not tuned in well has to have some tradeoffs in robustness compared with > critical to tune modes. Anyone have specific information about that? > > We probably should have tried even slower speeds because later on I had > great difficulty copying him and took lots of hits. He is running Linux > so did not have the FEC version of DEX. My experience in the past was > that the Viterbi codin
[digitalradio] MFSK16 tuning improvement, was:best mode to use for weak signal HF work and othe
Hi Patrick. I wonder whether it would make sense to improve MFSK16 to be more easy to use. The idea is to decode multiple streams in parallel as it is done in Olivia and pick the one with the best S/N. It seems to me that Olivia is only that much popular because it is a lot easier to tune than MFSK16. 73 and GL, Vojtech OK1IAK --- In digitalradio@yahoogroups.com, "Patrick Lindecker" <[EMAIL PROTECTED]> wrote: > > Hello Rick, > > >If often wonder if a mode that has a very wide ability to print even if > >not tuned in well has to have some tradeoffs in robustness compared with > >critical to tune modes. Anyone have specific information about that? > The ability of DominoEx to be tuned very easily is that the modulation is an IFK one and not a MFSK one. It means that you measure a difference of frequency not a frequency in absolute as in MFSK. The good point it is easy to tune (no absolute reference of frequency) but the bad point is that when you do an error, the second symbol is also in error...you double the error (it's a bit like in PSK31, which one measures a difference of phase: if you do a error on one symbol, the next symbol will be also in error). > > >Can anyone say with some degree of certainly what modes you think will > >get through on the low bands with high QRN levels? > I think Olivia must be good but Contestia is more close to ideal as twice quicker than Olivia with a minimum S/N just 1 or 1.5 dB superior to Olivia. > > 73 > Patrick > > > > - Original Message - > From: KV9U > To: digitalradio@yahoogroups.com > Sent: Friday, December 01, 2006 7:49 PM > Subject: Re: [digitalradio] best mode to use for weak signal HF work and other mode discussions > > > Brett, > > There are several sound card modes commonly used in addition to the most > popular PSK31 and 45 baud RTTY That would be MFSK16, Olivia, Hell, and > Throb/ThrobX. Although there are others, I rarely, if ever hear them. I > no longer seem to hear any MT-63 and the CHIP modes came and went quickly. > > I wanted to do more experimenting with DominoEX and last night I got to > work some 160 meter NVIS. We started out on MFSK16 but I have been > having a lot of problems with this mode as of late and maybe it is > because my soundcard is not calibrated correctly, but I find that I have > to use about 10 to 20 Hz offset RIT in order to print the other station. > MFSK16 really does require extremely accurate tuning of perhaps 4 Hz or > so. My rig is an ICOM 756 Pro 2 which is supposed to have very good > stability at 0.5 ppm. > > The other station and I tried some PSK31 for a short time when I lost > him on MFSK16 and was just able to get him to try DominoEX at 11 baud. > His signal was close to the noise although it was not that noisy on 160 > since we are in the winter season. The print was very poor at 11 baud, > so we dropped to 8 baud and things got better. Even at 8 baud, the speed > of transmission is still faster than MFSK16. We had a CW station come up > about 50 Hz below us and when that station was transmitting, it > drastically affected the print of the DEX mode, even at 8 wpm. The one > thing that DEX has going for it is that it is less critical to tune in. > > If often wonder if a mode that has a very wide ability to print even if > not tuned in well has to have some tradeoffs in robustness compared with > critical to tune modes. Anyone have specific information about that? > > We probably should have tried even slower speeds because later on I had > great difficulty copying him and took lots of hits. He is running Linux > so did not have the FEC version of DEX. My experience in the past was > that the Viterbi coding helps a great deal in good printing, even at 11 > baud, but of course your speed drops by all of 50% so you are just a bit > slower at 11 baud/FEC than you would be with MFSK16. > > It would be interesting to hear of other station's experience with DEX > and DEX/FEC and various speeds with and without FEC, particularly with > the lower baud rates on low band NVIS type operation. > > One of the things that I have to accept is that almost none of these > modes will work very well on the lower bands with high QRN levels from > summer static. > > Can anyone say with some degree of certainly what modes you think will > get through on the low bands with high QRN levels? > > 73, > > Rick, KV9U > > Brett Owen Rees VK2TMG wrote: > > > All, > > > > I find that I normally use PSK31 - as that is what most other stations > > use > > and is popular. But, I see a lot of stations that I cannot work - yet > > I can > > see their trace on the waterfall. Often, they are responding to my CQ and > > they just don't make it. Why do people respond to a 2 * 3 call with a > > 1*1 or > > 1*2 call? There seems to be a strategy for psk31 mode that involves >
