dear rick conventional dtmf does need a very good s/n ratio BUT in mftty there are slower modes with much less shift and very narrow filters so you can pick up a very low signal out of the noise you know surely if bandwith is getting lower the s/n increases i tested the soft "off-air" and i could detect a signal with my pc mic in front of pc speaker that i could not detect by ear ... and i had some background noise during the test cause my girlfriend was watching tv :-) i know that this is not a real test like testing it on the air but i am sure it will work for weak signals greetz dg9bfc sigi ----- Original Message ----- From: Rick W To: digitalradio@yahoogroups.com Sent: Thursday, January 15, 2009 10:43 PM Subject: Re: [digitalradio] Re: New MFTTY Version 30.145
DTMF tones are easy to distinguish for us OT's. Maybe not so easy for new digital hams, but and that might be a useful characteristic as long as it can compete well against the existing modes of which we have many, some with not that much difference in performance. A couple days ago I started working on a new document that looked at the various digital modes, particularly the sound card modes, to put some kind of perspective for hams new to digital modes. But after working on this for a while, I realized that there were only a few that do work well in terms of speed vs ISI vs Doppler, vs weak signal, vs bandwidth, etc., so it is nearly a moot point. And even though some modes are superior to other modes under some conditions, if no one uses them, then no matter how good they may be, it won't matter. Over the past few years, we have seen a new mode come along, get a lot of comments on groups like this one to try and coordinate with other hams, sometimes successfully and sometimes not. But after a few weeks, it dies down and you never hear much again. If I understand Patrick, F6CTE's critique of his implementation of DTMF, which has been in Multipsk for some time, this is not a weak signal mode and requires signals to be well above zero dB S/N. Or is this implementation that much different? I sure do not miss the green keys and my Model 15 TTY and homebrew TU and loop supply. I am totally sold on computer generated digital modes, especially the sound card modes that avoid vendor lock in and special hardware. 73, Rick, KV9U kh6ty wrote: > There is always a search for a "Holy Grail" of digital modes for ham radio, > with ease of use, performance, robustness, resistance to atmospheric > doppler, bandwidth, speed, FUN, etc! > > Personally, I just like the musical sound of MFTTY and appreciate the > uniqueness of Norbert's approach. Once the user friendliness gets ironed > out, I look forward to being able to find people using the mode often. MFTTY > is easily distinguishable from other modes - it sounds a little like Throb > perhaps, but not idential, so I do not think it is so much a "different > tongue" on the Tower of Babel that is difficult to distinguish on the > waterfall presentation, as some of the flavors of Olivia and DominoEx are. > > Other opinions may vary, of course, but my opinion is that I just ENJOY > using the mode. It probably will never be as popular as PSK31 for chatting, > but it definitely is FUN in my persoanl opinion! (I am one of those old guys > who started with a green key machine on RTTY and miss the clatter and smell > of the machine oil - but I also appreciate the progress in performance, > convenience, and friendliness of the soundcard modes). > > Let's all play with MFTTY and send Norbert our comments and suggestions. It > might turn out to be more than it appears at first glance. One thing is for > sure, Norbert has done a very complete and respectable job on these initial > beta implementations! > > 73, Skip KH6TY > >
