[digitalradio] Re: KV9U - MT63
Rick, You have done the tests and found that MT-63 is not very good at handling weak signals compared with other modes. It is less sensitive than others, but some of the most sensitive modes are not necessarily the best performers when conditions deteriorate. I think it's reasonably sensitive though. Is you recent on air testing to determine that or some other parameters, such as ability to handle interference, etc.? Not really. I pretty much know what to expect with MT63 because I've been using it since IZ8BLY first released it a long time ago. The most impressive thing about MT63 is how it seems to resist heavy static crashes. I made a few recordings with short segments of the signal removed to simulate this type of QRN and there was little effect on copy. It seems to withstand a lot more QRM than most and will usually print well with a good chunk of it's signal obliterated. There's a short video on this reflector in the file section showing how MT63 resists a combination of Pactor QRM and some fairly deep selective fading. By the way copying both you near noise level, and Skip, KH6TY, a bit stronger at S3-4. Tried to decode an earlier narrower mode but no luck. Was it MFSK8? That was DominoEX4. Please give us a call next time Rick! Tony -K2MO
RE: [digitalradio] Re: KV9U - MT63
Also the redundancy of the FEC treatment in MT-63 allows it to give 100% accuracy with 25% loss of data. In actual use, Olivia will do better under worse conditions at a large loss of speed. Contestia attempts to bridge the gap, but MT-63 gives the highest accurate through put at the highest speed before going to an ARQ protocol. David KD4NUE -Original Message- From: digitalradio@yahoogroups.com [mailto:digitalra...@yahoogroups.com] On Behalf Of Tony Sent: Saturday, March 21, 2009 3:41 AM To: digitalradio@yahoogroups.com Subject: [digitalradio] Re: KV9U - MT63 Rick, You have done the tests and found that MT-63 is not very good at handling weak signals compared with other modes. It is less sensitive than others, but some of the most sensitive modes are not necessarily the best performers when conditions deteriorate. I think it's reasonably sensitive though. Is you recent on air testing to determine that or some other parameters, such as ability to handle interference, etc.? Not really. I pretty much know what to expect with MT63 because I've been using it since IZ8BLY first released it a long time ago. The most impressive thing about MT63 is how it seems to resist heavy static crashes. I made a few recordings with short segments of the signal removed to simulate this type of QRN and there was little effect on copy. It seems to withstand a lot more QRM than most and will usually print well with a good chunk of it's signal obliterated. There's a short video on this reflector in the file section showing how MT63 resists a combination of Pactor QRM and some fairly deep selective fading. By the way copying both you near noise level, and Skip, KH6TY, a bit stronger at S3-4. Tried to decode an earlier narrower mode but no luck. Was it MFSK8? That was DominoEX4. Please give us a call next time Rick! Tony -K2MO
Re: [digitalradio] Re: KV9U - MT63
MARS has a different situation than the ham bands since you have a dedicated phone communications bandwidth channel. And from what I hear operators can use phone and data simultaneously with MT-63. We can not do that on the ham bands below VHF here in the U.S. I normally try to keep the modes at no wider than 500 Hz unless the selected band is very poor and there are few other stations. I can see using wider modes if they worked better but 2K MT-63 is even worse than 1K in terms of sensitivity and robustness. But it does have double the speed and sometimes you need that if conditions cooperate. Contestia is not able to handle even 7 bit ASCII, so I would consider it more for casual chatting or maybe for handling NTS traffic since the lowest common denominator is likely CW where you don't have case concerns. For the highest speed ARQ sound card mode, that works the deepest into the noise, have you considered FAE400? For better conditions you could move up to FAE2000 although five times wider for maybe 2X throughput? But at least what you get through is perfect copy and you can do both keyboard chatting and messaging at the same time. I don't think you can do that with any other sound card mode other than perhaps PSKmail on Linux? If PSKmail can eventually do peer to peer on MS Windows OS, that could change things a bit. 73, Rick, KV9U Cortland Richmond wrote: In MARS nets I've noticed MT63 2000 Hz with long interleave delivering surprisingly good performance. Here in Michigan Army MARS, we usually choose 1000 Hz long for normal training texts, but 2K for larger files. Cortland KA5S -Original Message- From: David Little Sent: Mar 21, 2009 8:56 AM To: digitalradio@yahoogroups.com Subject: RE: [digitalradio] Re: KV9U - MT63 Also the redundancy of the FEC treatment in MT-63 allows it to give 100% accuracy with 25% loss of data. In actual use, Olivia will do better under worse conditions at a large loss of speed. Contestia attempts to bridge the gap, but MT-63 gives the highest accurate through put at the highest speed before going to an ARQ protocol. David KD4NUE No virus found in this incoming message. Checked by AVG - www.avg.com Version: 8.0.238 / Virus Database: 270.11.22/2015 - Release Date: 03/20/09 19:01:00
RE: [digitalradio] Re: KV9U - MT63
Cortland, We also use it in Region 4, but mostly 1K long interleave. We have used 2k under good band conditions, and the speed is very impressive. We are also experimenting with the text transmission capabilities of Easypal. David KD4NUE -Original Message- From: digitalradio@yahoogroups.com [mailto:digitalra...@yahoogroups.com] On Behalf Of Cortland Richmond Sent: Saturday, March 21, 2009 1:29 PM To: digitalradio@yahoogroups.com Subject: RE: [digitalradio] Re: KV9U - MT63 In MARS nets I've noticed MT63 2000 Hz with long interleave delivering surprisingly good performance. Here in Michigan Army MARS, we usually choose 1000 Hz long for normal training texts, but 2K for larger files. Cortland KA5S -Original Message- From: David Little Sent: Mar 21, 2009 8:56 AM To: digitalradio@yahoogroups.com Subject: RE: [digitalradio] Re: KV9U - MT63 Also the redundancy of the FEC treatment in MT-63 allows it to give 100% accuracy with 25% loss of data. In actual use, Olivia will do better under worse conditions at a large loss of speed. Contestia attempts to bridge the gap, but MT-63 gives the highest accurate through put at the highest speed before going to an ARQ protocol. David KD4NUE
Re: [digitalradio] Re: KV9U - MT63
MT63 was I think the first really accessible I can't see it mode that could deliver printable copy. Our default *slow* digital mode is Olivia 32 bit 1K, but it is interesting that 16 bit is preferred by the cognoscenti. For relatively short messages, speed is of less concern and Olivia really shines in that application. I DL'd a Puppy Linux ISO image with FLDIGI for an Acer One, but have also an Acer One with XP, and a speedier laptop with Vista. The Acers with a six cell battery offer extended service life between recharges which together with Wilderness Protocol operation could allow service over quite a few days cut off from power. Not that we will need that ... It seems like only a few years (30 some!) ago I was reading paper tape and copying MARS traffic for Fort Hood by intercept. I also had a Kantronics UTU in my car, and sometimes delivered AMTOR MARSgrams received on the move and printed with a thermal printer. The Model 100 still works. When all else fails. Cheers, Cortland KA5S/AAR5UT -Original Message- From: Rick W mrf...@frontiernet.net Sent: Mar 21, 2009 2:35 PM To: digitalradio@yahoogroups.com Subject: Re: [digitalradio] Re: KV9U - MT63 MARS has a different situation than the ham bands since you have a dedicated phone communications bandwidth channel. And from what I hear operators can use phone and data simultaneously with MT-63. We can not do that on the ham bands below VHF here in the U.S. I normally try to keep the modes at no wider than 500 Hz unless the selected band is very poor and there are few other stations. I can see using wider modes if they worked better but 2K MT-63 is even worse than 1K in terms of sensitivity and robustness. But it does have double the speed and sometimes you need that if conditions cooperate. Contestia is not able to handle even 7 bit ASCII, so I would consider it more for casual chatting or maybe for handling NTS traffic since the lowest common denominator is likely CW where you don't have case concerns. For the highest speed ARQ sound card mode, that works the deepest into the noise, have you considered FAE400? For better conditions you could move up to FAE2000 although five times wider for maybe 2X throughput? But at least what you get through is perfect copy and you can do both keyboard chatting and messaging at the same time. I don't think you can do that with any other sound card mode other than perhaps PSKmail on Linux? If PSKmail can eventually do peer to peer on MS Windows OS, that could change things a bit. 73, Rick, KV9U
