View Full Version : MT-63 Question
Our local RACES group is setting up digital comms. Originally all the equipment had been ordered to run WL2K but there was a change of direction.
Now the group is looking into using MT-63.
So far my reading indicated that MT-63 needs to run on a sideband transmitter. My question is will it run on an FM transmitter?
73
Frank
n5rfx
09-28-2006, 09:38 PM
I assume by FM transmitter you are referring to an F3E transmitter like you would use on 2m meter or 440 repeaters? Yes is will work fine, but the FEC and interleaving are overkill for a full quieting channel. MT63 was designed to work in the HF bands where conditions are less than optimal. You can read about MT63 at http://www.qsl.net/zl1bpu/MT63/Technical.htm
73,
Mark N5RFX
I agree with Mark, that MT-63 is way overkill for a full-quieting FM mode. You might also want to investigate the various MFSK modes such as "Olivia" . You might even want to go to DRM protocols and see if it is possible to send files etc. with the mode. I would certainly check into the legalities of doing those things, but the technology is there. Make sure you aren't getting into hot water with the FCC or any OOs out there!
Good luck ! 73, Jim
Good point.
I have been talking with the powers that be in our RACES group and I didn't think MT-63 was the way to go considering what I have read.
Thanks
73
Frank
N5PVL
09-30-2006, 12:23 AM
I'm not sure if I understand correctly... Are you looking for a good digital mode to use over FM voice repeaters?
If so, then this article on mixed-mode operation (http://www.uspacket.org/mixmode.htm) may be of use to you. It describes the use of Q15x25 mode for 2.5kb digital communications over a voice repeater. - It also describes how to tie these communications in to a Packet Radio network, giving the voice repeater the functions of a Packet node.
Contact me if you decide to try this out... I think it's possible to get 3.0kb out of this setup but have not tested my theory yet.
I tried this system out and found it to be excellent for transferring files over an FM voice repeater.
KG4RUL
09-30-2006, 12:25 AM
MT63 is fast and fine to use. You don't need a connected mode like packet at all on FM. http://www.qrz.com/iB_html/non-cgi/emoticons/biggrin.gif
N5PVL
09-30-2006, 12:42 AM
What a connected mode gives you is error-free data transfers. - Reliably.
Sometimes accuracy can be important, so I wouldn't discount the connected modes just yet.
All the digital modes have thier special abilities, good points and bad points. - It's a tool box, full of tools that do different jobs in different ways.
I'm thinking that for FM, the importance of being able to do file transfers, rather than just plain text might be a factor. However, I am not that familiar with the FCC requirements on the VHF bands. Can you fill us in on that , Charles ? And of course, not all the protocols can do file transfers. That is one reason I mentioned DRM in a previous post. But again, I am not up to speed on the requirements as I haven't been interested in doing such a thing up to this point. But I may be gravitating toward it, so "inquiring minds want to know! "
73, Jim
N5PVL
09-30-2006, 04:14 AM
The rules for VHF/UHF are more relaxed than they are for HF, as mixed-mode communications are allowed on VHF/UHF frequencies, but not on the HF bands.
Other than that, I guess it's about the same in most respects. You get more bandwidth to play with on VHF/UHF, but I think that's more from the laws of physics rather than PART97.
One thing to be careful about is not to get the repeater trustee mad at you, if you are going to run mixed-mode over his repeater. Be sure to notify the guy or even better, ask first. Also, there are some repeater controller settings that can make mixed-mode operation difficult if not impossible to do. Because of this, some repeaters will work a lot better for mixed-mode operation than others. If you are on good terms with the repeater trustee, they can adjust the repeater controller's timing parameters and announcements so as to optimize the repeater for mixed-modes.
I tested the FlexNet/Q15x25 setup over the local voice repeater by transferring 10k text files, but it could have been graphics, executables or anything else. Q15x25 is an AX25 mode like Packet, which means that it has good error correction and can transfer any kind of file reliably.
There is a dll package for MixW that gives it Q15x25 capability. Once installed, it offers Q15x25 as a Packet modem option. This is the same software used by FlexNet for thier "Newqpsk" mode. They are identical in function, written by the same guy.
It's nice to speculate about this stuff but best of all is to get out there and see what works best. Two hams who both have MixW, a soundcard interface and VHF radios could test a number of modes and protocols and compare performance. - Just have a standard 10 or 20k test file that you transfer in simplex mode and then over a repeater with each mode or protocol in turn, keeping careful record of how fast or slow the file transfers went.
If you want to be meticulous, it is a good idea to run each test three times and then average the results. Check all received files each time for errors, whether the mode you test has error correction or not. Some error correction systems are more reliable than others, especially under unusual operating conditions like you would encounter while using a voice repeater.
As you can probably tell, I really like doing that kind of testing but unfortunately I am one of three amateurs living in my county. It's hard to get victims, er I mean volunteers for that kind of activity.
WIth good signal, MT63 is FAST. It has robust FEC too, so errors are few. Use the 2 KHz mode and you can send a long message faster than you could read the preamble by voice. Plus, you can just set the radio or mike next to a computer speaker, and the computer mike next to a rig for MT63. It's that easy. You might try it with HT's next to a laptop.
Cortland
KA5S
Will MT63 do file transfers ? I certainly remember packet being able to with a program called YAPP. I did my VHF experimenting years ago when packet came around the first time. But I haven't been involved in it at all lately. I'm glad to see an expert such as Charles on board !
I still think it would be great if a "fill in the blanks" file were prepared in Word™ and the document could be sent as a formated file rather than just plain text. Well, that is the way I would be approaching the whole thing. Ideas ? http://www.qrz.com/iB_html/non-cgi/emoticons/rock.gif
73, Jim
N5PVL
09-30-2006, 07:06 PM
MixW will send files in MT-63 mode, and IZ8BLY's dedicated MT63 Terminal program lets you specify a text or binary transfer.
I think a Word document would have to go as a binary file. The problem there is making sure everybody has a copy of Word, preferably the same version.
Would the RTF file format work out OK? Any Windows computer can deal with Rich Text Format files. Wordpad will read and write them.
Virtually any computer that is sold with the Windows™ operating system and an office suite of software is capable of working with Word™ documents. I only know of one or two people that I have any sort of contact with that are holdouts for WordPerfect™ although I personally like the software better, myself!
But I still think the "fill in the blanks" document is certainly a modern equivalent to the ARRL message #s .
Yup, I'm sure that all the formatting commands,etc that make up a RTF file would have to be sent in a binary formatted file transfer protocol.
N5PVL
10-01-2006, 02:40 PM
I read somewhere yesterday evening that MT63 was disqualified for use by MARS because it cannot offer sufficiently reliable error correction. - You can only expect so much from any FEC mode, and 100% correct copy at all times is just not one of those things you can expect.
It seems like it was Army MARS being mentioned, but I am not sure. I skimmed across the reference while looking for something else, so I didn't pick up much detail.
This is not by any means an attack on MT63, which is a great digital mode. If reliably accurate copy is not vitally important to what you are wanting to do, then I am certain that MT63 will handle your needs very well, as witnessed by enthusiastic reports from hams who have used it.
Sometimes 100% accurate copy is required and sometimes it really isn't.
My personal experience with MT63 only extends to a few QSOs on 20 and 30 meters. I was just ragchewing, and never did try to send any files. It worked OK for me but there I was, taking up enough bandwidth for ten or more PSK31 QSOs and not accomplishing anything that I couldn't have done just as well or better with one PSK31 stream.
If I had been interested in transferring data then I would have wanted good error correction, and if I was just ragchewing then I would want to be able to make contacts easily and not take up any more bandwidth than the task demands. - So for the things I was interested in doing, I never saw where they fit into MT63's capabilities and rather than misapply the mode, I went on to other digital modes that were better suited to the jobs I had in mind.
One really sad thing to see is where an amateur will develop a weird attachment to one particular digital mode and go forth to 'promote' that one mode above all others for each and every purpose. These hams try to get by with just one tool, seeing all the other tools in the box as 'competition' instead of simply being other tools, each with its own special utility for a particular need or situation.
Might as well just go ahead and shoot themselves in the foot.
There are so many misguided digital mode enthusiasts out to promote some mode or another at all of the other ones' expense that I no longer pay much attention to enthusiastic claims and disparaging comments, instead drawing my own conclusions after some personal experience.
We have migrated away from the basic science of testing and evaluating our tools, instead lurching over to a system of mindless promotion and propaganda campaigns. Why we have allowed ourselves to degenerate this way is a big mystery to me. It seems awfully stupid of us to drift into that kind of behavior when we were already set up with a long, honored tradition of doing things on a rational, scientific basis.
KG4RUL
10-02-2006, 11:30 AM
Charles appears to have missed the point of the original poster's question i.e. MT63 on FM!
A connected mode such as packet is overkill on FM. MT63 is fine and since it is a soundcard mode, it is usually easier to implement. http://www.qrz.com/iB_html/non-cgi/emoticons/biggrin.gif
Quote[/b] ]A connected mode such as packet is overkill on FM. MT63 is fine and since it is a soundcard mode, it is usually easier to implement.
The original packet network was over FM (simplex), and packet can be implemented with a sound card. Why are we wanting to jam up a perfectly good repeater with MT-63?
Quote[/b] (N5PVL @ Oct. 01 2006,10:40)]I read somewhere yesterday evening that MT63 was disqualified for use by MARS because it cannot offer sufficiently reliable error correction. - You can only expect so much from any FEC mode, and 100% correct copy at all times is just not one of those things you can expect.
MARS does use MT63 for traffic "real time." It's not suitable for unattended exchange of messages, because errors -- not unlikely on HF -- cannot be corrected in a timely manner.
However, nothing stands still, and there has been mention of an adaptive ARQ mode for MT63.
That said, it's easy to try out MT63 for this application. I say give it a try; they can always try something else. Just don't wait for a real emergency!
Cortland
KA5S/AAR9UT
N5PVL
10-02-2006, 12:37 PM
KG4RUL says:
Quote[/b] ]
Charles appears to have missed the #point of the original poster's question i.e. MT63 on FM!
KG4RUL appears to have a problem reading and comprehending english. - I responded to that question in a comprehensive manner.
N5PVL:
Quote[/b] ]
What a connected mode gives you is error-free data transfers. - Reliably.
Sometimes accuracy can be important, so I wouldn't discount the connected modes just yet.
N5PVL:
Quote[/b] ]
It's nice to speculate about this stuff but best of all is to get out there and see what works best. Two hams who both have MixW, a soundcard interface and VHF radios could test a number of modes and protocols and compare performance.
N5PVL:
Quote[/b] ]
MixW will send files in MT-63 mode, and IZ8BLY's dedicated MT63 Terminal program lets you specify a text or binary transfer.
N5PVL:
Quote[/b] ]
I read somewhere yesterday evening that MT63 was disqualified for use by MARS because it cannot offer sufficiently reliable error correction. - You can only expect so much from any FEC mode, and 100% correct copy at all times is just not one of those things you can expect.
It seems like it was Army MARS being mentioned, but I am not sure. I skimmed across the reference while looking for something else, so I didn't pick up much detail.
This is not by any means an attack on MT63, which is a great digital mode. If reliably accurate copy is not vitally important to what you are wanting to do, then I am certain that MT63 will handle your needs very well, as witnessed by enthusiastic reports from hams who have used it.
Sometimes 100% accurate copy is required and sometimes it really isn't.
- Which all apply quite well to the question about MT63. I noted that it was a great mode, but I did not gloss over the fact that FEC is not 100% effective. I encouraged experimentation not just with MT63, but with a variety of modes, and verified MT63's ability to transfer either text or binary files.
Not noted above is my discussion of the legal side of operating mixed-modes, a lesson on getting along with repeater trustees/owners and and example of an existing VHF mixed-mode file transfer setup that has been developed and tested on the air with another digital mode, Q15x25. This gives us a good base for comparing performance and ease of use with other digital modes like MT63 and others that you can easily try out with MixW.
I described a rough and ready method for comparing perfomance during file transfers that anybody can do, and the articles I referred to discuss timing factors that must be addressed in order to operate any digital mode over a voice repeater.
While I was at it, I also noted:
Quote[/b] ]
One really sad thing to see is where an amateur will develop a weird attachment to one particular digital mode and go forth to 'promote' that one mode above all others for each and every purpose. These hams try to get by with just one tool, seeing all the other tools in the box as 'competition' instead of simply being other tools, each with its own special utility for a particular need or situation.
Might as well just go ahead and shoot themselves in the foot.
One thing I didn't do was to act like a used-car salesman, trying to shill some pet digital mode. Personally, I don't believe in choosing which digital mode to use based upon which idiot screams the loudest so what I 'sell' instead is the notion of conducting a fair test to see which digital mode fits your particular needs the best. - It's easy and inexpensive to do and returns results that you can see and judge for yourself.
I hope that compiling this info will help you make a breakthrough on understanding what I have written in this topic, OM. #Re-read as necessary, and be sure to let us know if you have any more difficulty.
Thanks again everybody.
Good information to consider.
What the RACES RO is planning is a network of fixed sites around our county made up mostly of hospitals.
We currently have equipment that was origianlly intended for use with WINLINK but since you need an internet connection for that to work, it was decided to look for something that can be strictly radio to radio.
MT-63 seems to fill that requirement.
73
Frank
K0RGR
10-02-2006, 07:04 PM
You might want to try a program called ARES-Pack. It's a DOS program that will send and receive ARES messages via ordinary Packet.
I think I've seen that the downside of the program is that it is DOS-only - won't run correctly in WIndows compatibility mode, but I could be mistaken about that.
Overall, the application software that formats, sends, receives, and displays/prints the messages will be a bigger bugaboo than the protocol used to send it.
If you don't have MS Word, try the freeware Open Office. It's very MS compatible.
N5PVL
10-02-2006, 08:46 PM
AC3P says:
Quote[/b] ]
Thanks again everybody.
Good information to consider.
What the RACES RO is planning is a network of fixed sites around our county made up mostly of hospitals.
We currently have equipment that was origianlly intended for use with WINLINK but since you need an internet connection for that to work, it was decided to look for something that can be strictly radio to radio.
MT-63 seems to fill that requirement.
That sounds great, Frank. It sounds like your group is on the ball, and I'd like to wish you guys 'clear ether', as they used to say.
Once you get it all going, give us a report with setup info! - A lot of other groups appear to be interested in the same kind of thing, for the same reasons.