Home |
Search |
Today's Posts |
#11
|
|||
|
|||
Extension of PSK segment
John Smith I wrote:
wrote: ... "The market" spoke very clearly, in the form of comments to FCC. The CTT proposal was overwhelmingly opposed. About 7 out of 8 comments on it clearly said NO. Sounds like a clear message from the market to me! 73 de Jim, N2EY However, if a new market comes forth, one composed of amateurs with little or no knowledge of CW and only using digital voice and digital data transmission--it would be market controlled also, and one would suspect it would self-correct and frown on the use of the bands for wasteful analog and cw communications. I would disagree. Those modes are not wasteful. On the other hand, a vision of using the HF bands for data transmission would indeed be a way of filling up our bands pretty quickly, and for not a lot of gain. If I'm interested in Data Transmission, I would design a system for frequencies where there is less natural noise - VHF and up. Then bandwidth issues would be less of a problem too. Let's face it, digital voice is the only way to go. I would disagree. What I have seen in digital voice so far offers no particular advantage over SSB, unless we are talking about digital for it's own sake. Most schemes that I have seen have some fatal flaws, such as the received transmission must be received in toto - IOW if you don't catch the beginning, you don't catch anything. The solution to that would be channelizing HF, or assigning specific frequencies to Digital voice. In addition, unless there have been some big advances recently, Digital voice does not have any particular bandwidth advantages. Give me a Digital voice mode that I can tune across the band and pick up a conversation at any point in the transmission, and a 1 KHz or less bandwidth signal, and then I'll be interested. And of course, I'll need to see that some other folks are buying the digital radios too, so I'll have people to talk to. PSK is too slow for data transmission of LARGE and multi-megabyte amounts of data, end of story. As for PSK, you are correct that it is too slow for data transmission. But that little 31 baud signal was never intended for Data transmission. It was intended for correctable text at a rate that a reasonably proficient typist could tap away at the keyboard in real time. Also a mode that can be efficiently operated at QRP and lover levels. And for that, it is an excellent mode. - 73 de Mike KB3EIA - |
#12
|
|||
|
|||
Extension of PSK segment
On Mar 15, 7:44 pm, wrote:
. Sounds like a clear message from the market to me! Actually I suspect it is a clear message from the embedded "gentlemen". 73, de Hans, K0HB |
#13
|
|||
|
|||
Extension of PSK segment
On Mar 15, 11:38�pm, John Smith I wrote:
wrote: "The market" spoke very clearly, in the form of comments to FCC. The CTT proposal was overwhelmingly opposed. About 7 out of 8 comments on it clearly said NO. Sounds like a clear message from the market to me! 73 de Jim, N2EY However, if a new market comes forth, one composed of amateurs with little or no knowledge of CW and only using digital voice and digital data transmission--it would be market controlled also, and one would suspect it would self-correct and frown on the use of the bands for wasteful analog and cw communications. If a new market appears, use of various modes will change, and the new market can propose rules changes to FCC. If a new market really does emerge, such proposal will be widely supported in the comments. However, it seems to me that the "new market" may be more of an illusion than a reality. We've had PCs in hamshacks for a couple decades now, and yet the popularity of analog modes doesn't seem to be declining. I recall being told, 20+ years ago, that there would soon be a national highspeed digital amateur radio packet network using VHF and UHF that would turn HF into a backup system. Never happened. As for "wasteful analog and cw communications" - why do you call them wasteful? Can a real-time digital voice message be sent in the width of an SSB voice signal and result in the same effectiveness? (signal to noise, power requirements, lack of need to synchronize, tolerance of interference and fading, etc.)? Is there any non-text data mode (IOW, something you listen to rather than look at) which can replace Morse Code? Should AM voice be banned from amateur radio? How about FM voice? Let's face it, digital voice is the only way to go. Why? And which kind of digital voice? Why can't there be a choice of modes - digital, analog, old, new - available to hams? *PSK is too slow for data transmission of LARGE and multi-megabyte amounts of data, end of story. Not the end of the story at all. Yes, PSK31 is too slow for large amounts of data - because it wasn't designed for that. PSK31 was designed to be a keyboard-to-keyboard mode that uses very little bandwidth and has excellent performance with low S/N ratios. It was meant as an improvement to FSK RTTY for such QSOs. For real-time (live) QSOs, PSK31 is fast enough. An "industry standard" for encryption/compaction and decryption/de-compaction still needs to come forth to deal with HIGH transfer rates of digital voice and data transmission and availability to ALL hardware/software developers/manufacturers be assured to such a standard(s) ... Yup. And that's the "who's going to tie the bell on the cat" question. Who will come up with that standard? That's the key question to the whole issue. Who is going to do all that development work and then give it away free? G3PLX and a small group did it for PSK31. Great care needs to exercised when proposing and developing acceptable schemes to the above, we certainly don't need to create a "tower of babel" by not having free access to algorithms and standard methods in common use--and free use and experimentation needs to be right up front and encouraged--this only holds with the tradition of amateur radio! Agreed! And it's already been established as a tradition. PSK-31 is a classic example. Everything about it is wide open and free-for-the-download. OTOH, Pactor 2/3 is not free at all. Implementing it requires buying a specific hardware modem that is rather pricey. Some may say that $600 for a modem isn't much in the scheme of things, but even if that's true, it's the principle of proprietary methods that goes against the grain. btw, there is a downside to all this digital stuff. With 'analog' modes, such as AM, FM, SSB and Morse Code, anyone with a suitable receiver can hear amateur communications as they were meant to be heard. Tuning in SSB requires a specialized technique, and *understanding* Morse Code requires learning a skill or using a decoder, but all that is needed to receive them is a suitable receiver. IOW, they're wide open. With digital modes, the incoming message is incomprehensible without a decoding device - usually a computer. That creates a divide between those who are equipped and those who aren't. Some may think this is trivial in a world where computers are all over the place. And perhaps it is. But it may not be a trivial thing at all. In the days when AM voice was *the* voice mode used by hams on HF, amateur radio got a lot of new hams from folks who heard hams talking on their 'shortwave' receivers. That source all but disappeared when SSB replaced AM, because most SWLs couldn't receive SSB. More recently, we've gotten new hams from the ranks of the scanner folks, because they could hear amateur FM repeaters. Going digital would eliminate most of that. IOW, watch out for the Law of Unintentional Consequences. 73 de Jim, N2EY |
#14
|
|||
|
|||
Extension of PSK segment
In article .com,
wrote: Can a real-time digital voice message be sent in the width of an SSB voice signal and result in the same effectiveness? (signal to noise, power requirements, lack of need to synchronize, tolerance of interference and fading, etc.)? The review of DRM-based digital voice in this month's QST makes a point of noting that both the WinDRM and hardware-modem-based systems require a pretty clean, fade-free propagation path in order to perform well. On less clean paths, they're prone to drop out... I infer that as soon as the facing or QRM is severe enough to overcome the forward error correction coding, you lose an entire packet. Not the end of the story at all. Yes, PSK31 is too slow for large amounts of data - because it wasn't designed for that. PSK31 was designed to be a keyboard-to-keyboard mode that uses very little bandwidth and has excellent performance with low S/N ratios. It was meant as an improvement to FSK RTTY for such QSOs. I've heard of at least two groups who have been working on a PSK31-based bulk data transmission system - both systems uses both forward error correction and an ACK/NAK protocol structure. It's not intended for megabytes of data, but for semi-unattended transmission of modest amounts of data during emergencies. For example, basic health&welfare traffic (queries and "We're OK, are in the shelter" responses) can be entered via online Web forms, the fields converted to a compact representation and heavily compressed, and then sent out in big batches via PSK31 or a similar narrow-bandwidth mode. The idea isn't to replace SSB voice (or CW net traffic) but to supplement it, reducing the operators' workload and reducing errors. It's certainly not intended as a substitute for broadband! Yup. And that's the "who's going to tie the bell on the cat" question. Who will come up with that standard? That's the key question to the whole issue. Who is going to do all that development work and then give it away free? G3PLX and a small group did it for PSK31. Agreed! And it's already been established as a tradition. PSK-31 is a classic example. Everything about it is wide open and free-for-the-download. OTOH, Pactor 2/3 is not free at all. Implementing it requires buying a specific hardware modem that is rather pricey. Some may say that $600 for a modem isn't much in the scheme of things, but even if that's true, it's the principle of proprietary methods that goes against the grain. There was some work going on towards an open-source higher-speed HF-data protocol a couple of years ago - SCAMP. If I recall correctly it's based on OFDM (like DRM) with heavy use of forward error correction. The last I heard of it, it had worked out well under clean-pathway conditions, but wasn't working all that well under noisy/fade-prone conditions and wasn't yet considered "ready for prime time" or (as yet) a serious competitor to Pactor 2/3. Haven't heard anything more about it in the last year or so - it's possible that development has stalled. IOW, watch out for the Law of Unintentional Consequences. a.k.a. "Oops!" :-) -- Dave Platt AE6EO Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior I do _not_ wish to receive unsolicited commercial email, and I will boycott any company which has the gall to send me such ads! |
#15
|
|||
|
|||
Extension of PSK segment
wrote in message oups.com... On Mar 15, 11:38�pm, John Smith I wrote: wrote: [snip] PSK is too slow for data transmission of LARGE and multi-megabyte amounts of data, end of story. Not the end of the story at all. Yes, PSK31 is too slow for large amounts of data - because it wasn't designed for that. PSK31 was designed to be a keyboard-to-keyboard mode that uses very little bandwidth and has excellent performance with low S/N ratios. It was meant as an improvement to FSK RTTY for such QSOs. My question on this is why would we be sending large amounts of data on amateur radio? The need for it doesn't exist in general. If it did, someone would have developed the appropriate digital mode by now. Dee, N8UZE |
#16
|
|||
|
|||
Extension of PSK segment
On Mar 17, 2:19�am, "Dee Flint" wrote:
My question on this is why would we be sending large amounts of data on amateur radio? * I can think of a couple uses for it, Dee. First there's emergency/public service comms. The served agencies are used to being able to send emails with sizable attachments through the usual networks. A mode that would let them do that via amateur radio when the usual networks are not available would be a really good tool in the emcomm toolbox. IMHO it's the thinking pushing WinLink. Second, there are plenty of times in an ordinary QSO when it would be good to be able to send a picture, station description, article, a sound clip, etc. directly by radio, and have it in digital format at the other end. In the past, such modes as SSTV have gained limited acceptance because they required lots of extra apparatus, but with the widespread acceptance of PCs today the big limitation is software, not hardware. The need for it doesn't exist in general. In some cases, if something is presented to people, they will find a use for it. Look back on predictions about computers - in the early '50s it was predicted that a half- dozen or so general-purpose computers would serve all the needs of the USA, and in the '70s it was said that no ordinary person would ever need a computer in their home. Both pronouncements were made by knowledgeable professionals, and at the time seemed quite reasonable. Of course "if you build it, they will come" doesn't always work out. *If it did, someone would have developed the appropriate digital mode by now. I disagree. One of the big problems is that such development tends to be protected by the developers, and *not* made open-source. PSK-31 and Linux are exceptions, not the rule. In the bad old days, the focus was on hardware, and the idea of controlling a mode-concept wasn't taken too seriously. SSB, FM, SSTV, RTTY, AX.25 packet, etc., all came to amateur radio essentially as freebies. The standard was widely and publicly available, just meet it and go on the air. But you can't homebrew a Pactor 2/3 modem today the way you could homebrew an SSB rig 50 years ago. The "bell-the-cat" question is still *who* is going to develop such new modes and then just give them away for free. Groups that have tried (TAPR and the spread-spectrum idea) have taken years without much to show. All IMHO 73 de Jim, N2EY |
#17
|
|||
|
|||
Extension of PSK segment
"Dee Flint" wrote in message
[snip] My question on this is why would we be sending large amounts of data on amateur radio? The need for it doesn't exist in general. If it did, someone would have developed the appropriate digital mode by now. Dee, N8UZE Erm.... Packet Radio..?! I ran a packet BBS for 11 years, ok so it was slow (1200/9600 bd) but it was reliable and transmitted a *lot* of data (ok most of it rubbish, but what the heck..?!) 73 Ivor G6URP |
#18
|
|||
|
|||
Extension of PSK segment
|
#19
|
|||
|
|||
Extension of PSK segment
On Mar 17, 1:19 am, "Dee Flint" wrote:
My question on this is why would we be sending large amounts of data on amateur radio? "Because we can" Actually, I agree that there may be no particular ongoing NEED for an Amateur Radio high volume data channel, but neither was there a NEED for LEOs, APRS, and similar "tinkerer" modes, many of which had their genesis in ham shacks and now have morphed into commercial applications. I believe that the rules for Amateur Radio regulations should be loosened to the "least required to protect other spectrum users" with the intention to promote a renewed spirit of experimentation by hams. 73, de Hans, K0HB |
#20
|
|||
|
|||
Extension of PSK segment
wrote in message ups.com... On Mar 17, 2:19�am, "Dee Flint" wrote: My question on this is why would we be sending large amounts of data on amateur radio? I can think of a couple uses for it, Dee. First there's emergency/public service comms. The served agencies are used to being able to send emails with sizable attachments through the usual networks. A mode that would let them do that via amateur radio when the usual networks are not available would be a really good tool in the emcomm toolbox. IMHO it's the thinking pushing WinLink. Perhaps they would like to have such but IMHO, when the catastrophe is serious enough and wide spread enough that hams are truly needed, that is apt to be coupled with power source limitations that would make it unwise to send such length attachments in many cases. Plain ascii text would be the most useful and results in low file size. There are several modes that can handle that. In addition, the power source limitations might make running computers as well as radios an unwise choice in some situations. Second, there are plenty of times in an ordinary QSO when it would be good to be able to send a picture, station description, article, a sound clip, etc. directly by radio, and have it in digital format at the other end. In the past, such modes as SSTV have gained limited acceptance because they required lots of extra apparatus, but with the widespread acceptance of PCs today the big limitation is software, not hardware. Yes the PC capabilities have done a lot for digital modes of all types. The need for it doesn't exist in general. In some cases, if something is presented to people, they will find a use for it. Look back on predictions about computers - in the early '50s it was predicted that a half- dozen or so general-purpose computers would serve all the needs of the USA, and in the '70s it was said that no ordinary person would ever need a computer in their home. Both pronouncements were made by knowledgeable professionals, and at the time seemed quite reasonable. Well the science fiction authors were envisioning small personal size computers almost from the day computers were invented. I must have read a lot of it as I've always believed that computers would become an everyday tool for everyone. Of course "if you build it, they will come" doesn't always work out. If it did, someone would have developed the appropriate digital mode by now. I disagree. One of the big problems is that such development tends to be protected by the developers, and *not* made open-source. PSK-31 and Linux are exceptions, not the rule. Well I disagree with your disagreement. To me it seems that there are enough hams that somewhere in that group are several people capable of doing this it they deemed it worth doing. Then we would have modes and software developed by hams for hams. Then there would be more likelihood that it would be shared in the same manner as PSK-31. There is nothing stopping anyone from doing that development other than lack of interest. etc., all came to amateur radio essentially as freebies. The standard was widely and publicly available, just meet it and go on the air. But you can't homebrew a Pactor 2/3 modem today the way you could homebrew an SSB rig 50 years ago. Well the today's computer capabilities, the hardware aspect simply goes away. It becomes a software issue. The "bell-the-cat" question is still *who* is going to develop such new modes and then just give them away for free. Groups that have tried (TAPR and the spread-spectrum idea) have taken years without much to show. I think the problem with the spread-spectrum is that for ham radio operators, the usefulness simply doesn't justify setting up to use it. People want to get out there and find stations rather than having to have pre-arranged schedules for everything. If it doesn't seem useful to them, people will pass on it. This occurs in all fields of endeavor. A person has a bright idea, packages it, markets it, and it doesn't sell simply because the market doesn't perceive any significant need for or pleasure derived from the product. Dee, N8UZE |
Reply |
Thread Tools | Search this Thread |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Forum | |||
PBS's Newshour 15 min segment on VOA-BBG (FRI 26 JAN)? Do mpeg copies exist (that are fully downloadable)? | Shortwave | |||
aluminium element segment corrosion & weather proofing... ? | Antenna | |||
Dipole Extension | Antenna | |||
dipole extension? | Antenna | |||
Daws Butler will be the subject of today's ALL THINGS CONSIDERED segment. | Broadcasting |