Walt, I am mostly figuring it as a data file for the higher speed modes, since most of us can not type all that fast. I have found that for me, about 40 wpm is all I need for Keyboard to Keyboard and that includes some in the type ahead buffer responding to the other station as I receive their text. I find Olivia at around 20 to 30 wpm too slow but much above 50 or 60 to way faster than needed. The exception would be if I wanted to send an image. Then it is hard to have anything too fast:)
From what the developers of the amateur radio digital software modes have told us, they are primarily interested in keyboard only and are not interested in emergency or bbs type use. That is why we have PSK31, Olivia, MFSK16, etc. We don't have any ARQ keyboard mode yet although SCAMP was operated close to that for testing where you could connect and send a message. Changing a mode to send a file would be very disruptive and not the most ideal situation. Since we are likely to be using 500 Hz and narrower digital modes here in the U.S. on any of the data/CW areas, it would be very useful to have a mode that could transparently switch as needed although insuring a clear frequency will be something requiring operator control. Because we typically have waterfalls on our screen when using computer generated modes, this is quite easy to do since the slightest carrier or signal will show up on screen. In order to have a really robust and accurate mode, I would like to see an ARQ mode 500 Hz or less. This would allow for a good throughput and error free data and images, etc. Consider that you can get at least four 500 Hz signals in the width of one voice signal. The 100 KHz digital/CW area of 80 meters could nearly handle 2 signals per kilohertz or close to 200 simultaenous contacts which is actually greater than the 400 KHz voice carrying capacity of the expanded phone bands CW is a special case because except for the 60 meter band, it is permitted on any frequency that you are licensed for. I have been on phone traffic nets where CW stations have checked in, but it is rare. Same thing with some other casual groups hang out. DuBose Walt Civ AETC CONS/LGCA wrote: >Rick, > >Did you figure this as a text/data file being sent or a keyboard-to-keyboard >mode. > >I think that there has to be some operator thought concerning wheather or not >they are going to be operating in a "chat" QSO or data trasnfer mode. But the >condition certainly has to be considered if there is a chat QSO and then one >of the operators wants to send a file. Do they change modes or use the same >mode? > >I believe that this is an operator consideration and not a decision that >software would make. > >Maybe if you contemplate sending data you should start a chat QSO in the wider >mode. > >I don't think we should make operator (operations) decisions strictly based on >mode; but, suggested operating decisions should be made. > >Should I be prevented from using CW on the phone band to QSO with a friend who >is running SSB? How many have operated a voice net where an operator checks >in on CW because they can't talk? > >Walt/K5YFW > >-----Original Message----- >From: [email protected] >[mailto:[EMAIL PROTECTED] Behalf Of KV9U >Sent: Sunday, October 22, 2006 11:56 AM >To: [email protected] >Subject: Re: [digitalradio] 3kHz or 500Hz Re: Updates on effect of FCC >R&O > > >There is a grain of truth in the concept of the wider BW protocol >working more efficiently than a narrower one. But this is primarily for >a special case where it is a "many to one" situation such as between >users of an e-mail system, examples being Winlink 2000, PSKmail, JNOS2, >etc., or BBS store and forward systems such as the Aplink, Winlink, and >packet BBS HF systems, mostly from the past. If there were many users >needing to make a connection with the limited resource, (the connecting >server), then a faster mode would be more convenient. > >But it assumes that there is a very limited resource to connect to. Even >then, you are going to be using many times as much bandwidth with the >wider mode. In terms of bandwidth vs. throughput, the faster mode can >never equal the narrower mode since it doesn't always even run that much >faster and there are certain procedural things that take about the same >amount of time. > >Back when we used the old Aplink and Winlink systems, it was common to >have to wait to either find adequate propagation or an open server. It >was very common for me to be able to connect from SW Wisconsin to Bud in >Las Vegas, NV than to connect to a much closer Illinois station who I >never seemed to be able to connect. > >Using the RF Footprint concept of Rick Muething, KN6KB, the current >principal programmer for the Winlink 2000 system and developer of the >SCAMP Sound Card Amateur Messaging Protocol mode, even under good >conditions, Pactor III is only a bit better than Pactor 2. He uses the >metric of KHz per second and rates various modes as follows: > >Pactor 3 10 KHz-sec >Pactor 2 14 >RDFT 23 >Pactor 1 28 >HF Packet 46 >PSK31 62 >MT-63 110 > >Now you should know that he also allows for a 200 Hz guard band between >signals and that is of course not necessary in all modes and that is why >it makes the wider modes appear more favorable. And remember that this >is for good conditions, something that is often just not available on HF >with perhaps > 10 db S/N. Under difficult conditions, which he does not >delineate, you would find some significant deterioration of the Pactor >modes. SCAMP and Packet would become completely inoperative. Although >Pactor modes are the primary ARQ modes available to hams at this time, >there is the PSKmail sound card mode with most of the ASCII character set. > >When it comes to two hams using digital modes on RF, then the slower, >but much narrower bandwidth modes are a much more efficient use of the >spectrum because you are sharing the limited resource of bandwidth >rather than the limited resource of an RF to internet server. Compare >the number of PSK31 stations that can fit into what would only be one >Pactor 3, wide band Olivia, or MT-63 signal. Just imagine if those PSK31 >ops have one large message to send to one other op. Would they be better >off waiting to use a mode that was over 20 times wider in bandwith? In >other words, would it be possible to get more data through the wide band >mode, with that many connections if you had to wait your turn to use >the only one big pipe rather than many smaller pipes? The answer >obviously is no. There are many other issues, such as making the >connection and negotiating real time issues before you actually make the >transfer of data. > >And that is for good conditions. Under 0 db S/N conditions, P3 drops way >down to perhaps 20 cps and P2 half that at around 8 cps. This is based >upon the slowest speeds available (most robust for difficult conditions) >as shown on the SCS website. I would suggest that at this point the >wider modes would be much slower, in terms of total throughput, with say >10 users (waiting their turn) and a bandwidth of 2.4 KHz than with >narrower methods such as PSKmail with its ARQ PSK63 modulation. > >Sincerely, > >Rick, KV9U > > > Need a Digital mode QSO? Connect to Telnet://cluster.dynalias.org Other areas of interest: The MixW Reflector : http://groups.yahoo.com/group/themixwgroup/ DigiPol: http://groups.yahoo.com/group/Digipol (band plan policy discussion) Yahoo! 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