I think that for the speed, MT-63 can be OK. But not that great with difficult conditions. A lot of modes will work find with good paths. I suspect that they have reasonably strong signals. MT-63 just does not reach down into the noise as some other modes and I have tested it many times under many conditions to reach that conclusion.
The MIL-STD 188-110 single tone modem is something that I would like to test. It is very odd to me why we are not hearing at least a few who are doing this. I very much want to see how well it works compared to other modes. I realize it is a very wide mode since it was designed to take up most of a full voice bandwidth for commercial/government use. Just because it always runs at 2400 baud symbol rate and is illegal to use here in the U.S. on the text digital portions of the bands does not mean it can not be used in the voice/image portions of the bands to at least send pictures. Why do you suppose that it is not being at least tested? I have asked this many times and have yet to have one person respond with their experiences. 73, Rick, KV9U Steve Hajducek wrote: > Hi Rick, > > You obviously do not use MT-63 to pass book traffic on a daily basis > on NVIS paths, fore if you did your opinion would be completely > different and if you don't believe me, just ask any MARS member that > is using a Sound Card based system these days and they will tell you > just how robust MT-63 is for an FEC protocol. > > As to MIL-STD-188-110 serial tone modem and associated protocols, > being as not only FEC but ARQ is provided and with data rates down to > 75bps, it is extremely robust, granted 75bps is rather slow, but it > just can not be stopped, 75bps is know as ROBUST mode by the way, > there is no PSK carrier frequency and its a psuedo spread spectrum > waveform within a 3Khz channel, even in MARS-ALE at 75bps its always > 3Khz as you can't diddle with the carrier and symbol rate which don't > exist as such at higher data rates. > > /s/ Steve, N2CKH > > At 05:51 PM 10/27/2007, you wrote: > >> Steve, >> >> If MT-63 is robust relative to MIL-STD-188-110, then the latter may not >> be all that robust! I do not find MT-63 to be all that robust, and it is >> not as sensitive as other modes since it does not work well into the noise. >> >> Do you have any real world amateur tests yet on the MIL-STD-188-110 >> modems using the PC-ALE software approach? >> >> I have tested this out on 6 meters and it seems to transmit OK. I don't >> have anyone close by with the capability to run the program who can also >> operate digital modes. >> >> Also, have you found anyone who has run this software on HF here in the >> U.S. in the voice/image portions of the bands? >> >> It has been several weeks and I have not received any response back from >> ARRL yet on my tentative submission to the FCC for an interpretation of >> these regulations. Perhaps some are holding back because they consider >> the modes not legal in the voice/image areas? My reading of the rules >> says that it should be proper to use this software. >> >> Do you (or anyone else) have any thoughts as to why these modes are not >> being at least tested on HF? >> >> 73, >> >> Rick, KV9U >> > > > >
