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 jgorman01 wrote: >A couple of comments. The FCC must consider more than just how fast >data can be sent. It must also consider how to maximize the numbers >of users that can access a finite spectrum without waiting. > >Your point assumes there is queuing system of some sort for that 3 kHz >of spectrum and that people will stand in line to use the frequency. >In amateur radio there is no queuing system, you can only monitor a >frequency until the qso finishes. There is no "grab a number" system >to determine who uses it next. And, since qso's are generally random >length, you may have to wait one minute or 30 minutes. The >traditional way of bypassing this is to move to a clear frequency. > >It seems obvious to me that the FCC has decided that much more >bandwidth for phone users is needed versus bandwidth for CW/RTTY/data >(i.e., narrow bandwidth) users and that the narrow bandwidth segment >should be shrunk. In doing so, they needed to decide how to "best" >use the smaller spectrum, and that part of the determination was how >to minimize the wait time for spectrum for the most users. > >I'm old enough to remember 2, 4, and even 8 party telephone lines. Do >you know how much time was wasted in checking the line to see if it >was not being used? There were lots of times it was quicker to drive >to a neighbors or to town rather than wait for the line to clear. >Frustration to the max! Telephone companies have dealt with >maximizing the use on shared facilities for over a hundred years. >They have sophisticated analysis tools that into account all kinds of >variables. However, cusomter wait times is still the one variable >that drives everything else. > >I'll bet I'm not the only ham who would chose wait time for an open >frequency as being more important than length of qso. Perhaps the FCC >is "encouraging" hams to develop a method of queuing for frequencies >and qso times thereby maximizing spectrum use. I suspect a system >like this would go a long way to letting the FCC expand bandwidths. > >Jim >WA0LYK > >--- In digitalradio@yahoogroups.com, "expeditionradio" ><[EMAIL PROTECTED]> wrote: > > >>There's another way to look at spectrum use. It is better to use a >>3kHz bandwith for 10 minutes than to use a 500Hz bandwidth for 1 hour >>to pass the same traffic. On HF, with short propagation openings, it >>is better to be able to quickly send the message. Approximately 3kHz >>is the defacto worldwide bandwidth standard for HF communication >>transceivers. >> >>This R&O isn't an issue of FCC making rules for "encouragement" to >>produce narrower bandwidth signals. It is the result of someone at FCC >>that is out of touch with reality. >> >>The Bigger Issue: The freedom to use existing digital worldwide >>standards for HF communications is important for Amateur Radio. >> >>It is very much like the freedom to use existing analog bandwidth >>standards such as SSB and AM voice. Should FCC take take that freedom >>away also, under the guise of "encouraging innovation"? Should hams be >>forced to develop 500Hz bandwidth voice modes? >> >>Or, should a wide range of communications methods be "encouraged" in >>USA like it is in the rest of the civilized world? >> >>Bonnie KQ6XA >> >> >> Need a Digital mode QSO? 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