RE: [digitalradio] 16QPSK Modulation and Baud
I have talked to some scientist at a large research independent facility who are doing HF modem research for the government. Here is some of what they believe... For a broadcast mode, use heavy FEC. If the receiving stations have transmit capability, let them NAK missed data periodically. For individual or group connections, use a small to moderate amount of FEC with CRC and ARQ based on NAKs rather than ACKs. Start off with moderate FEC and send 3-7 frames depending on the length/size of your frame. Short frames send 7, long frames send 3. If no station sends a NAK, send 6-14 frames. If no NAKS, send 12-28 frames, etc. If at any time only one NAK from one station, resend the frame and continue on. If you are for example sending 6-14 frames and receive two NAKs, back off to 3-7 frames. If sending 12-28 frames and receive two or more NAKs, back off to 6-12 frames OR just drop back to 3-7 frames. They also recommend manually setting a real-time propagation index for the frequency used and base your baud rate on that or use a fixed baud rate for various MUFs or bands. There was much discussion among the group concerning using varying baud rates or a single baud rate. About half felt that a 45.5 baud rate (or perhaps 31 baud rate) should be used on HF. The other half thought that 31, 45, 90 and 180 baud rates could be used. For their testing using a channel simulator close to a Watson channel simulator (they tested to a poor CCIR channel with varying fading, noise, etc. with a goal of 0 to -10 dB SNR). Their modem manually switched baud rates depending on the frequency (band) used and of course the band chosen was based on the projected path distance and MUF. Their transmission length were from 10-30 seconds. I don't know how many frames they sent but I do know that a 10 second transmission took 15 seconds to decode with moderate to heavy FEC in the broadcast mode. Their 30 second transmission produced a little over two pages (72-76 characters per line and 60 lines per page) of ASCII characters. They were getting 3 bits of information per tone and were using multi-tone. They said that their mode use much like OFDM and I am almost sure they were using somewhere between 50-80 tones. Their ultimate goal was a full page of ASCII characters being decoded in less than 15 seconds in a broadcast mode. The did mention the error rate but don't know what it was...but I am almost sure that had to be less than 1 character per page considering the type of information the system was to send. I wish I could tell you more, but the entire project is considered intellectual property by the research organization. Walt/K5YFW -Original Message- From: digitalradio@yahoogroups.com [mailto:[EMAIL PROTECTED] Sent: Tuesday, September 19, 2006 3:04 PM To: digitalradio@yahoogroups.com Subject: Re: [digitalradio] 16QPSK Modulation and Baud Jose Amador wrote: Taking adventage of SCS experience, they chose PSK (cannot tell by heart if differential or not, a peek to the manual is needed) as a modem, and depending on the retry rate (closely related to BER) it tries more complex constellations and more carriers. One of the secrets is the switchover criteria...when retries rise, then jump to the next lower speed, whatever it means. I think that FEC could be used wisely... For instance: Initially, use ARQ, with the modulation A, working at A bauds. When retries rise, enable FEC dinamically. If it fails again, jump to the lower speed, or even to another stronger modulation (versus noise, I mean). When the retries diminish, it may try with more carriers, or more complex constellations, or more speed. The key is to do it automatically, or adaptatively. The switchover criteria is the most complex problem... but it could be reached even with the trial and error mode. 73 de Nestor, CM3NA __ XIII Convención Científica de Ingeniería y Arquitectura 28/noviembre al 1/diciembre de 2006 Cujae, Ciudad de la Habana, Cuba http://www.cujae.edu.cu/eventos/convencion 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! Groups Links 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! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/digitalradio/ * Your email settings: Individual Email | Traditional * To change settings online go to: http://groups.yahoo.com/group/digitalradio/join (Yahoo! ID required) * To change settings via email: mailto:[EMAIL PROTECTED] mailto:[EMAIL
RE: [digitalradio] 16QPSK Modulation and Baud
You are right Erik...the problem is that all NWS offices are using the same equipment and same forecasting models, computer programs and all require specific information. There are a couple of hams working at Texas AM Univ in their weather labs that are also computer experts and digital data experts on both V/UHF, microwave and HF. They understand the problem and can't come up with a solution to the problem. With hundreds of NWS offices using the same equipment and methods, if you change one or two, you really need to change all. Again, I agree with you that we need to look for ways to shrink their data needs...but then you will have to understand the complexities of their data modeling programs and the input data it needs and convince the NWS that they need to change their modeling program and weather prediction program and methods. I'm not sure that I want to go there. Walt/K5YFW -Original Message- From: digitalradio@yahoogroups.com [mailto:[EMAIL PROTECTED] Sent: Tuesday, September 19, 2006 7:10 PM To: digitalradio@yahoogroups.com Subject: Re: [digitalradio] 16QPSK Modulation and Baud Walt, I don't doubt that the source data is 20K/Minute or greater, what I question is whether or not sending the 'source' is necessary? It seems to me that you are asking us to find ways to solve a problem, it often helps to step back and look at the problem and ask questions. I make my living as a consulting engineer, and I know I exasperate many of my clients on the first day I walk into a project because, rather than following their predetermined thought processes, I make it a point to question their thought processes. Basically, I define and solve problems, and help implement solutions for a living. It is not unusual for the solutions I engineer to differ greatly from my clients preconceived notions of what they initially thought they needed, but I do solve their problems. What I question is whether or not we shouldn't look at technology solutions that for instance don't require transmission of 20K/Minute of text, but still solve the problem. Especially for a weather system (I've lived through hurricanes, and spent a fair amount of time in tornado alley as well, so I do understand the importance of this information to public safety), it seems that what we are monitoring is a changing system, we might be able to come up with a data model of it that may be a little more granular, be represented by a lot less data, and still get the job done. We often have more sensors and more precision available to us than we need to make decisions, sometimes we need to trim the data. When normal comms are functioning 100% sending the full data with the greatest precision possible is great, when the normal comms fail, we are left in a fall back position. If we allow our 'fall back data channel' to choke because we are trying to provide a 100% solution, haven't we failed our mission? What if we could condense or abbreviate our data stream significantly, wouldn't it be a worthwhile effort to pursue? Engineering is a discipline of making the appropriate economic trade offs, we live in an era of the information age where data memory, storage, and processing capacity are extremely cheap. Usually bandwidth is cheap as well, so we have a certain mindset about not spending effort or money to maximize its efficient use. In this case though, bandwidth isn't cheap, one could argue that from a public safety point of view, it may be the most precious of resources, which leads me back to my point... is it not possible to spend money and processing power on finding a way to greatly reduce the size of a data frame, thereby reducing the bandwidth requirements of the system? Isn't it possible that effort in this direction might yield the greatest overall system performance. 73, Erik KI4HMS DuBose Walt Civ AETC CONS/LGCA wrote: Erik, Send me your E-Mail address and I will send you an 40K sample file of NWS data in csv (delimited text format) that represents 2 minutes of WX radar data. I would never want to send this to the entire net. Walt/K5YFW 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! Groups Links 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! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/digitalradio/ * Your email settings: Individual Email | Traditional * To change settings online go to: http://groups.yahoo.com/group/digitalradio/join (Yahoo! ID required) * To change settings via
RE: [digitalradio] 16QPSK Modulation and Baud
Packet COULD have been a solution, but had a modulation format unable to do the job. As a MultiPSK user, I think that PSK31 is inadequate, maybe PSKFEC could perform better, but I would try PAX. It has some long keying delays I don't like from the moment you press the ENTER key, but is an ARQ mode capable of providing error less reception. I did not evaluate it in depth, but I did like the results I saw. So, if the need is to transfer a file and comment it afterwards, maybe that's one solution already at hand that should be evaluated. Jose, CO2JA --- DuBose Walt Civ AETC CONS/LGCA [EMAIL PROTECTED] wrote: Bill, In the past the HF communications between the NWS offices via amateur radio has been voice because there was not a reliable data mode available to them. In exercises they have tried PSK31 but were not satisfied with the results. They have not tried MT63 thus far. I because none of the operators are familiar with it and they based their use on PSK31 on the advice of the ARRL Section Emergency Coordinator and Section Manager. They also considered using Pactor III but for some reason the NWS didn't buy into it. The NWS wants DATA and Voice on the same channel...send data and then discuss the data. The same is true for HAZMAT teams wanting to talk to state, federal and other HAZMAT experts about an existing condition. The data they want to send is also very large and after the parties have the data, they want to discuss it via voice communications. I've seen the same scenario many times when a two doctors are looking at the same X-Ray, MRI or CAT-scan and are discussion it on the telephone. This is the world we live in and when it comes to decisions that the NWS or HAZMAT team make can save or cause the loss of many lives, they want what they want and nothing is going to change that. If we can't help out in this area, then we need to flat out say we can't and only try to produce new HF data techniques that meet our amateur radio of personal needs. Walt/K5YFW __ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com 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! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/digitalradio/ * Your email settings: Individual Email | Traditional * To change settings online go to: http://groups.yahoo.com/group/digitalradio/join (Yahoo! ID required) * To change settings via email: mailto:[EMAIL PROTECTED] mailto:[EMAIL PROTECTED] * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
Re: [digitalradio] 16QPSK Modulation and Baud
Can you or anyone explain why they need this high speed on HF when even 300 baud is pushing the limit on the higher HF bands? I think this limit only applies to protocols that do not make use of FEC, redundancy and adaptive training. Adaptive training may be the most important element. 73, Mark N5RFX 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! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/digitalradio/ * Your email settings: Individual Email | Traditional * To change settings online go to: http://groups.yahoo.com/group/digitalradio/join (Yahoo! ID required) * To change settings via email: mailto:[EMAIL PROTECTED] mailto:[EMAIL PROTECTED] * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
RE: [digitalradio] 16QPSK Modulation and Baud
Let me give one incident where high through put would be most desirable... When hurricanes hit the Texas Gulf Coast, all but radio communications can be lost between Brownsville, Texas to Houston, Texas. The weather stations there may have their eather radars operational but unable to send the picture or data to other weather stations. A highspeed, error free, robust, realtime, HF data mode is needed. The radar information may be 7.50 K bytes or larger. This data would need to be repeated every 5-10 minutes during critial stages of a hurricane. Walt/K5YFW -Original Message- From: digitalradio@yahoogroups.com [mailto:[EMAIL PROTECTED] Sent: Tuesday, September 19, 2006 7:38 AM To: digitalradio@yahoogroups.com Subject: Re: [digitalradio] 16QPSK Modulation and Baud Can you or anyone explain why they need this high speed on HF when even 300 baud is pushing the limit on the higher HF bands? I think this limit only applies to protocols that do not make use of FEC, redundancy and adaptive training. Adaptive training may be the most important element. 73, Mark N5RFX 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! Groups Links 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! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/digitalradio/ * Your email settings: Individual Email | Traditional * To change settings online go to: http://groups.yahoo.com/group/digitalradio/join (Yahoo! ID required) * To change settings via email: mailto:[EMAIL PROTECTED] mailto:[EMAIL PROTECTED] * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
RE: [digitalradio] 16QPSK Modulation and Baud
Walt- I will agree that this is a desirable capability, and I will agree that Hams should *Within reason* provide emergency Comms, but I DO NOT see this scenario as a proper part of Ham service. Especially if it requires drastic changes in our service constraints. Really- this is an extreme case, and I am truly surprised at you for putting it out as a serious option. (Or, was it?) Bill-W4BSG At 09:41 AM 9/19/2006 -0500, you wrote: Let me give one incident where high through put would be most desirable... When hurricanes hit the Texas Gulf Coast, all but radio communications can be lost between Brownsville, Texas to Houston, Texas. The weather stations there may have their eather radars operational but unable to send the picture or data to other weather stations. A highspeed, error free, robust, realtime, HF data mode is needed. The radar information may be 7.50 K bytes or larger. This data would need to be repeated every 5-10 minutes during critial stages of a hurricane. Walt/K5YFW Bill Aycock - W4BSG Woodville, Alabama 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! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/digitalradio/ * Your email settings: Individual Email | Traditional * To change settings online go to: http://groups.yahoo.com/group/digitalradio/join (Yahoo! ID required) * To change settings via email: mailto:[EMAIL PROTECTED] mailto:[EMAIL PROTECTED] * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
Re: [digitalradio] 16QPSK Modulation and Baud
I have been looking through the internet to find more information on all these alphabet soup modems. Here is a very interesting web site that lists not only the various types of waveform bps rates, but also the S/N ratio for these modems to work properly. Unfortunately, the baud rate is never mentioned: http://www.rapidm.com/standard_performances.shtml#STANAG%204285 If I am reading this information correctly, these modems don't have much application for what we have been talking about here. They require VERY high S/N ratios to work for any kind of speed. Like 10 to nearly 30 db. In fact, the very best they can do at the 75 bps rate, is around -5 db S/N with the particular modem product. And that is better than the requirements of the standard. After all the talk for weeks about how we need to get out of the technology jail that Bonnie keeps claiming, I question whether we will want to run 2400 baud modems on HF frequencies except in special cases such as when we are operating under the best conditions and very close to the MUF. These modes are supposed to be able to run under multipath spreads of 5 to 10 ms. Even with serious coding, one wonders how you can do that with a baud rate of under 0.4 ms if you use a baud rate of 2400? What would be the point of doing this when we have modes that go way, way, deep into the noise that are already available to us? The typical waveforms are just like the ones we already use, e.g., BPSK, QPSK, 8PSK, 16QAM, etc. Isn't much of this already available with the digital data transfer programs already available to the amateur community? Either RDFT types such as Digtrx, or QAM types such as Windrm? 73, 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! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/digitalradio/ * Your email settings: Individual Email | Traditional * To change settings online go to: http://groups.yahoo.com/group/digitalradio/join (Yahoo! ID required) * To change settings via email: mailto:[EMAIL PROTECTED] mailto:[EMAIL PROTECTED] * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
RE: [digitalradio] 16QPSK Modulation and Baud
Oh...Ok. The highest baud rate used on a multi-tone is 45.5 baud. For the serial tone modes, I don't know the answer. In the multi tone modes, the baud rate is addative. I understand Clover II as you describe it. I just looked at the original papers that I cot from HAL a few years ago. In MT63 the baud is addative and I suppose you could say that all tones are transmitted at once if you looked at a 3 KHz bandspread. But if you looked at the signal as the detector does, through an FFT with a narrow bandspread, I believe that it would appear that each tone appears at a different time. Is there where we get into a time domain, frequency domain or phase domain discussion? Someone who understands serial tone modems needs to explain just how they work...I will again look at the FS-1052 specs and see if I can learn more...or perhaps google for serial tone modulation. Walt/K5YFW -Original Message- From: digitalradio@yahoogroups.com [mailto:[EMAIL PROTECTED] Sent: Tuesday, September 19, 2006 12:25 PM To: digitalradio@yahoogroups.com Subject: Re: [digitalradio] 16QPSK Modulation and Baud You are misinterpreting what I was asking. Probably because I did a poor explanation. What I am asking, and no one seems to confirm, is whether or not the MIL or STANAG modems really are running at multi thousand baud rates on HF frequencies, or whether they are adding up the individual baud rates of the tones and claiming that as the baud rate? As an example, the Clover II waveform has four tones that operate at 31.25 baud. The total speed of the protocol varies depending upon which modulation scheme is being used at a given time. It can vary from 2DPSM to 16PSM with an extra 4ASM. Only one tone is operating at a given time. Thus the claim that the baud rate is always 31.25. With parallel tone modems do you have something similar, but there are many tones operating at the same time but perhaps at a moderate baud rate? Then do you add up the baud rates of each tone to total the waveform baud rate? Is that how they come up with using multi thousand baud rates on HF? Or are MIL and STANAG modems running multi thousand baud rates for a given tone? 73, Rick, KV9U DuBose Walt Civ AETC CONS/LGCA wrote: Let me give one incident where high through put would be most desirable... When hurricanes hit the Texas Gulf Coast, all but radio communications can be lost between Brownsville, Texas to Houston, Texas. The weather stations there may have their eather radars operational but unable to send the picture or data to other weather stations. A highspeed, error free, robust, realtime, HF data mode is needed. The radar information may be 7.50 K bytes or larger. This data would need to be repeated every 5-10 minutes during critial stages of a hurricane. Walt/K5YFW -Original Message- From: digitalradio@yahoogroups.com [mailto:[EMAIL PROTECTED] Sent: Tuesday, September 19, 2006 7:38 AM To: digitalradio@yahoogroups.com Subject: Re: [digitalradio] 16QPSK Modulation and Baud Can you or anyone explain why they need this high speed on HF when even 300 baud is pushing the limit on the higher HF bands? I think this limit only applies to protocols that do not make use of FEC, redundancy and adaptive training. Adaptive training may be the most important element. 73, Mark N5RFX 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! Groups Links 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! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/digitalradio/ * Your email settings: Individual Email | Traditional * To change settings online go to: http://groups.yahoo.com/group/digitalradio/join (Yahoo! ID required) * To change settings via email: mailto:[EMAIL PROTECTED] mailto:[EMAIL PROTECTED] * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
RE: [digitalradio] 16QPSK Modulation and Baud
Bill, My scenerio is exact what has been done an several occasions...first starting with a senior metorogilist sitting at the San Antonio Weather Serive L Band radar and talking on 40 and 75 meters (through W5SC) to the NWS Office in Brownsville...W5??. Then 8-9 years later, a ham at the NWS in New Braunsfels let one of the NWS guys talk on his HF rig again to the NWS in Brownsville...this time feeding data from the EWX SAn Antonio-Austin Doppler Radar to Brownsville. Late, perhaps 2-3 years later, the NWS office in New Barunfels, using their own amateur radio callsign and HF equipment, gave vital weather information to the NWS office in Corpus Christi, Texas. In all three of these cases, the NWS offices could not contact each other by the Internet or telephone. The only communications they had was via amateur radio. Real stuff Bill...it happens and is likely to happen again. But giving critical weather information by voice isn't nearly what is desired...near realtime data can prevent the loss of many lives. Walt/K5YFW -Original Message- From: digitalradio@yahoogroups.com [mailto:[EMAIL PROTECTED] Sent: Tuesday, September 19, 2006 12:14 PM To: digitalradio@yahoogroups.com Subject: RE: [digitalradio] 16QPSK Modulation and Baud Walt- I will agree that this is a desirable capability, and I will agree that Hams should *Within reason* provide emergency Comms, but I DO NOT see this scenario as a proper part of Ham service. Especially if it requires drastic changes in our service constraints. Really- this is an extreme case, and I am truly surprised at you for putting it out as a serious option. (Or, was it?) Bill-W4BSG At 09:41 AM 9/19/2006 -0500, you wrote: Let me give one incident where high through put would be most desirable... When hurricanes hit the Texas Gulf Coast, all but radio communications can be lost between Brownsville, Texas to Houston, Texas. The weather stations there may have their eather radars operational but unable to send the picture or data to other weather stations. A highspeed, error free, robust, realtime, HF data mode is needed. The radar information may be 7.50 K bytes or larger. This data would need to be repeated every 5-10 minutes during critial stages of a hurricane. Walt/K5YFW Bill Aycock - W4BSG Woodville, Alabama 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! Groups Links 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! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/digitalradio/ * Your email settings: Individual Email | Traditional * To change settings online go to: http://groups.yahoo.com/group/digitalradio/join (Yahoo! ID required) * To change settings via email: mailto:[EMAIL PROTECTED] mailto:[EMAIL PROTECTED] * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
RE: [digitalradio] 16QPSK Modulation and Baud
--- DuBose Walt Civ AETC CONS/LGCA [EMAIL PROTECTED] wrote: Ok Jose and everyone...let's take a poll or have some SWAGs. So what do YOU (plural) think is the best modulation technique to use for a NEW and BETTER HF data mode? I believe there is no single best mode. Like in antennas, that you must trade gain for F/B, seems to me you must trade speed and BER depending on the channel conditions at a particular moment. Taking adventage of SCS experience, they chose PSK (cannot tell by heart if differential or not, a peek to the manual is needed) as a modem, and depending on the retry rate (closely related to BER) it tries more complex constellations and more carriers. One of the secrets is the switchover criteria...when retries rise, then jump to the next lower speed, whatever it means. Maybe it could take some experimentation to decide which modulation format, other than a single one (PSK) would be advisable for low frequency, noisy bands. There, MFSK seems to have an edge. So far, I have seen no adaptativeness in MFSK modes. I believe, based on what I have seen on MFSK and Olivia, that a slow channel with no retries could be a good solution when other solutions fail. So, I see at least two different scenarios. Clean bands, closer to the MUF, and dirty bands, close to the LUF. PSK QPSK DBPSK DQPSK (Dairy Queen PSK...Dairy Queen is an ice cream franchise) 8DPSK DQPSK 8QPSK 16QPSK And by the way, the Russians have a 96 tone HF data mode that is suppose to have great throughput, is very robust and is wider than 4 KHz. They love big, either it be trucks, planes or rockets Concerning baud... If the MUF is 32 MHz, then I believe that it is reasonable to think that 300 or 400 baud might work well on 10M...but on 40M and 80M it flat won't work. On 10 and 15 meters, 1200 baud works like a charm. So at 40 and 80M we will probably find that 45.5 baud works rather well. Some might suggest that 31 baud is better. I remember some newsgroup mails regarding using the PK-232 at 100 baud with packet. If it had become more common, maybe it would have bought HF packet a longer lease of life. I don't know how we can really find out what baud is best for each band and even if we want to. Maybe we want to take a SWAG and have a different baud for every band? That's probably a bad idea. But what about 31 or 45 baud for 80-20M, 90 baud for 30M-15M and 200 baud for higher bands...we can make the baud rate manual or automatically selectable. For a basic or start, I would recommend manually selecting baud rates. I recommend automatic...SCS has proven it can be done. The switchover criteria must be identified. My gut feeling is to start slow...play it safe to start with...31 or 45 baud all bands. Choose a good modulation technique...one that where you can manage the detection. Choose a method of FEC and add ARQ. You can see if you get better quality (error free copy) with or without ARQ, with or with FEC, etc. I would say that in lack of a better method, gut feelings are better than no feeling at all...your proposal seems reasonable and agrees with what I have seen. ARQ is NECESSARY for message integrity. FEC may or may not be necessary, depending on the channel conditions. Unneeded FEC will lower the thruput, while properly applied FEC will save retries. Choose a standard test text for testing and of course make sure that the chat mode works because after all, we DO (at least most hams) like to chat at bit. The KEY to any adventure is to have a goal and the flexibility to make changes as you go and work with as many as you can to evaluate what you create. I would call that evolution Once a mode have shown what it can do, i.e. established its capability, then change to some other configuration. AND REMEMBER, IT NOT A BAD THING TO FAST FAIL A BAD IDEA. Ask Werner von Braun about it If something doesn't work as good as you have, deep six it...don't carry on with a bad idea. Its not a bad thing to say that you idea didn't work. It avoids losing time on a failed theory. Those who are very technically astute, you will have to bring things such as throughput, and robustness, etc, down to terms that everyone can relate to. How about it? Are we (hams), as a group, up to creating a better communications mode? I know we can. 73, Walt/K5YFW 73 de Jose, CO2JA __ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com 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! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/digitalradio/ * Your email settings: Individual Email |
Re: [digitalradio] 16QPSK Modulation and Baud
--- Mark Miller [EMAIL PROTECTED] wrote: Can you or anyone explain why they need this high speed on HF when even 300 baud is pushing the limit on the higher HF bands? On the contrary, it is worse on the LOWER bands. I think this limit only applies to protocols that do not make use of FEC, redundancy and adaptive training. Adaptive training may be the most important element. Of course 73, Mark N5RFX Jose, CO2JA __ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com 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! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/digitalradio/ * Your email settings: Individual Email | Traditional * To change settings online go to: http://groups.yahoo.com/group/digitalradio/join (Yahoo! ID required) * To change settings via email: mailto:[EMAIL PROTECTED] mailto:[EMAIL PROTECTED] * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
RE: [digitalradio] 16QPSK Modulation and Baud
--- DuBose Walt Civ AETC CONS/LGCA [EMAIL PROTECTED] wrote: Let me give one incident where high through put would be most desirable... When hurricanes hit the Texas Gulf Coast, all but radio communications can be lost between Brownsville, Texas to Houston, Texas. The weather stations there may have their eather radars operational but unable to send the picture or data to other weather stations. A highspeed, error free, robust, realtime, HF data mode is needed. The radar information may be 7.50 K bytes or larger. This data would need to be repeated every 5-10 minutes during critial stages of a hurricane. Walt/K5YFW It was needed to be done here, during the passage of hurricane Ivan, the only communications link between La Bajada meteo radar station in the western tip of Cuba and INSMET in Havana was a NVIS link on HF ham radio frequencies, IN VOICE. Telephone and microwave relay towers fell with the wind gusts. The NHC in Miami also received that data. It would be more reliable to do it with a robust data link. But a similar scenario happened here, hurricanes use to do that... Jose, CO2JA __ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com 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! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/digitalradio/ * Your email settings: Individual Email | Traditional * To change settings online go to: http://groups.yahoo.com/group/digitalradio/join (Yahoo! ID required) * To change settings via email: mailto:[EMAIL PROTECTED] mailto:[EMAIL PROTECTED] * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
Re: [digitalradio] 16QPSK Modulation and Baud
You say A highspeed, error free, robust, realtime, HF data mode is needed. Why would the radar images have to be digital? It's not perfect data, but continuously changing. When I view radar and satellite imagery of storms on my television set, the signal I receive isn't digital, and it doesn't need to be for me to get full benefit of the information. It seems to me that digital is only 'really' important when you need an exact perfect copy, and usually when perfect copy is needed, the messages are a lot smaller and concise? Perfect digital copy is important where the purity of the received data places public safety at risk, but I really can't see real time weather radar info's data purity being that critical. Erik KI4HMS DuBose Walt Civ AETC CONS/LGCA wrote: Let me give one incident where high through put would be most desirable... When hurricanes hit the Texas Gulf Coast, all but radio communications can be lost between Brownsville, Texas to Houston, Texas. The weather stations there may have their eather radars operational but unable to send the picture or data to other weather stations. A highspeed, error free, robust, realtime, HF data mode is needed. The radar information may be 7.50 K bytes or larger. This data would need to be repeated every 5-10 minutes during critial stages of a hurricane. Walt/K5YFW 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! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/digitalradio/ * Your email settings: Individual Email | Traditional * To change settings online go to: http://groups.yahoo.com/group/digitalradio/join (Yahoo! ID required) * To change settings via email: mailto:[EMAIL PROTECTED] mailto:[EMAIL PROTECTED] * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
Re: [digitalradio] 16QPSK Modulation and Baud
MIL-STD 188-141 http://tracebase.nmsu.edu/hf/standards/MIL/141Bn1.pdf . MIL-STD 188-110 http://tracebase.nmsu.edu/hf/standards/MIL/188-110B.pdf 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! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/digitalradio/ * Your email settings: Individual Email | Traditional * To change settings online go to: http://groups.yahoo.com/group/digitalradio/join (Yahoo! ID required) * To change settings via email: mailto:[EMAIL PROTECTED] mailto:[EMAIL PROTECTED] * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
Re: [digitalradio] 16QPSK Modulation and Baud
--- KV9U [EMAIL PROTECTED] wrote: You are misinterpreting what I was asking. Probably because I did a poor explanation. What I am asking, and no one seems to confirm, is whether or not the MIL or STANAG modems really are running at multi thousand baud rates on HF frequencies, or whether they are adding up the individual baud rates of the tones and claiming that as the baud rate? As an example, the Clover II waveform has four tones that operate at 31.25 baud. The total speed of the protocol varies depending upon which modulation scheme is being used at a given time. It can vary from 2DPSM to 16PSM with an extra 4ASM. Only one tone is operating at a given time. Thus the claim that the baud rate is always 31.25. With parallel tone modems do you have something similar, but there are many tones operating at the same time but perhaps at a moderate baud rate? Then do you add up the baud rates of each tone to total the waveform baud rate? Is that how they come up with using multi thousand baud rates on HF? Or are MIL and STANAG modems running multi thousand baud rates for a given tone? Multiple carriers and complex PSK constellations give the SCS boxes that high speed capability. Carry it a bit further ahead. Broadcasters are using 460 slow keyed carriers with OFDM on a 10 kHz channel for Digital Radio Mondiale, an alternative to digital medium and short wave broadcasting to give CD quality audio. The mono audio stream on the main service channel is around 20 kbps. 73, Jose __ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com 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! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/digitalradio/ * Your email settings: Individual Email | Traditional * To change settings online go to: http://groups.yahoo.com/group/digitalradio/join (Yahoo! ID required) * To change settings via email: mailto:[EMAIL PROTECTED] mailto:[EMAIL PROTECTED] * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
RE: [digitalradio] 16QPSK Modulation and Baud
Erik, Send me your E-Mail address and I will send you an 40K sample file of NWS data in csv (delimited text format) that represents 2 minutes of WX radar data. I would never want to send this to the entire net. Walt/K5YFW -Original Message- From: digitalradio@yahoogroups.com [mailto:[EMAIL PROTECTED] Sent: Tuesday, September 19, 2006 2:37 PM To: digitalradio@yahoogroups.com Subject: Re: [digitalradio] 16QPSK Modulation and Baud You say A highspeed, error free, robust, realtime, HF data mode is needed. Why would the radar images have to be digital? It's not perfect data, but continuously changing. When I view radar and satellite imagery of storms on my television set, the signal I receive isn't digital, and it doesn't need to be for me to get full benefit of the information. It seems to me that digital is only 'really' important when you need an exact perfect copy, and usually when perfect copy is needed, the messages are a lot smaller and concise? Perfect digital copy is important where the purity of the received data places public safety at risk, but I really can't see real time weather radar info's data purity being that critical. Erik KI4HMS DuBose Walt Civ AETC CONS/LGCA wrote: Let me give one incident where high through put would be most desirable... When hurricanes hit the Texas Gulf Coast, all but radio communications can be lost between Brownsville, Texas to Houston, Texas. The weather stations there may have their eather radars operational but unable to send the picture or data to other weather stations. A highspeed, error free, robust, realtime, HF data mode is needed. The radar information may be 7.50 K bytes or larger. This data would need to be repeated every 5-10 minutes during critial stages of a hurricane. Walt/K5YFW 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! Groups Links 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! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/digitalradio/ * Your email settings: Individual Email | Traditional * To change settings online go to: http://groups.yahoo.com/group/digitalradio/join (Yahoo! ID required) * To change settings via email: mailto:[EMAIL PROTECTED] mailto:[EMAIL PROTECTED] * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
Re: [digitalradio] 16QPSK Modulation and Baud
Jose Amador wrote: Taking adventage of SCS experience, they chose PSK (cannot tell by heart if differential or not, a peek to the manual is needed) as a modem, and depending on the retry rate (closely related to BER) it tries more complex constellations and more carriers. One of the secrets is the switchover criteria...when retries rise, then jump to the next lower speed, whatever it means. I think that FEC could be used wisely... For instance: Initially, use ARQ, with the modulation A, working at A bauds. When retries rise, enable FEC dinamically. If it fails again, jump to the lower speed, or even to another stronger modulation (versus noise, I mean). When the retries diminish, it may try with more carriers, or more complex constellations, or more speed. The key is to do it automatically, or adaptatively. The switchover criteria is the most complex problem... but it could be reached even with the trial and error mode. 73 de Nestor, CM3NA __ XIII Convención Científica de Ingeniería y Arquitectura 28/noviembre al 1/diciembre de 2006 Cujae, Ciudad de la Habana, Cuba http://www.cujae.edu.cu/eventos/convencion 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! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/digitalradio/ * Your email settings: Individual Email | Traditional * To change settings online go to: http://groups.yahoo.com/group/digitalradio/join (Yahoo! ID required) * To change settings via email: mailto:[EMAIL PROTECTED] mailto:[EMAIL PROTECTED] * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
Re: [digitalradio] 16QPSK Modulation and Baud
Walt, I don't doubt that the source data is 20K/Minute or greater, what I question is whether or not sending the 'source' is necessary? It seems to me that you are asking us to find ways to solve a problem, it often helps to step back and look at the problem and ask questions. I make my living as a consulting engineer, and I know I exasperate many of my clients on the first day I walk into a project because, rather than following their predetermined thought processes, I make it a point to question their thought processes. Basically, I define and solve problems, and help implement solutions for a living. It is not unusual for the solutions I engineer to differ greatly from my clients preconceived notions of what they initially thought they needed, but I do solve their problems. What I question is whether or not we shouldn't look at technology solutions that for instance don't require transmission of 20K/Minute of text, but still solve the problem. Especially for a weather system (I've lived through hurricanes, and spent a fair amount of time in tornado alley as well, so I do understand the importance of this information to public safety), it seems that what we are monitoring is a changing system, we might be able to come up with a data model of it that may be a little more granular, be represented by a lot less data, and still get the job done. We often have more sensors and more precision available to us than we need to make decisions, sometimes we need to trim the data. When normal comms are functioning 100% sending the full data with the greatest precision possible is great, when the normal comms fail, we are left in a fall back position. If we allow our 'fall back data channel' to choke because we are trying to provide a 100% solution, haven't we failed our mission? What if we could condense or abbreviate our data stream significantly, wouldn't it be a worthwhile effort to pursue? Engineering is a discipline of making the appropriate economic trade offs, we live in an era of the information age where data memory, storage, and processing capacity are extremely cheap. Usually bandwidth is cheap as well, so we have a certain mindset about not spending effort or money to maximize its efficient use. In this case though, bandwidth isn't cheap, one could argue that from a public safety point of view, it may be the most precious of resources, which leads me back to my point... is it not possible to spend money and processing power on finding a way to greatly reduce the size of a data frame, thereby reducing the bandwidth requirements of the system? Isn't it possible that effort in this direction might yield the greatest overall system performance. 73, Erik KI4HMS DuBose Walt Civ AETC CONS/LGCA wrote: Erik, Send me your E-Mail address and I will send you an 40K sample file of NWS data in csv (delimited text format) that represents 2 minutes of WX radar data. I would never want to send this to the entire net. Walt/K5YFW 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! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/digitalradio/ * Your email settings: Individual Email | Traditional * To change settings online go to: http://groups.yahoo.com/group/digitalradio/join (Yahoo! ID required) * To change settings via email: mailto:[EMAIL PROTECTED] mailto:[EMAIL PROTECTED] * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
RE: [digitalradio] 16QPSK Modulation and Baud
Walt- All that is fine, but, unless I am badly off base, your examples are all voice Comms, not digital. I can support that 100%. Or did I miss something? My problem is in changing the structure of most of Ham radio to accommodate features that should be a part of the official infrastructure, as redundant capability, in the first place. It's not anything new to the Government service- let them ask NASA- I have watched unbroken visual coverage of live Shuttle operations through multiple orbits. To do that, they had to use multiple paths and links, so someone out there knows how. Those procedures can be transferred to surface-based, dedicated channels outside the Ham bands. We can help with trained Operators and back-up, but in their spectrum, like MARS. Bill-W4BSG At 01:53 PM 9/19/2006 -0500, you wrote: Bill, My scenerio is exact what has been done an several occasions...first starting with a senior metorogilist sitting at the San Antonio Weather Serive L Band radar and talking on 40 and 75 meters (through W5SC) to the NWS Office in Brownsville...W5??. Then 8-9 years later, a ham at the NWS in New Braunsfels let one of the NWS guys talk on his HF rig again to the NWS in Brownsville...this time feeding data from the EWX SAn Antonio-Austin Doppler Radar to Brownsville. Late, perhaps 2-3 years later, the NWS office in New Barunfels, using their own amateur radio callsign and HF equipment, gave vital weather information to the NWS office in Corpus Christi, Texas. In all three of these cases, the NWS offices could not contact each other by the Internet or telephone. The only communications they had was via amateur radio. Real stuff Bill...it happens and is likely to happen again. But giving critical weather information by voice isn't nearly what is desired...near realtime data can prevent the loss of many lives. Walt/K5YFW -Original Message- From: digitalradio@yahoogroups.com [mailto:[EMAIL PROTECTED] Sent: Tuesday, September 19, 2006 12:14 PM To: digitalradio@yahoogroups.com Subject: RE: [digitalradio] 16QPSK Modulation and Baud Walt- I will agree that this is a desirable capability, and I will agree that Hams should *Within reason* provide emergency Comms, but I DO NOT see this scenario as a proper part of Ham service. Especially if it requires drastic changes in our service constraints. Really- this is an extreme case, and I am truly surprised at you for putting it out as a serious option. (Or, was it?) Bill-W4BSG At 09:41 AM 9/19/2006 -0500, you wrote: Let me give one incident where high through put would be most desirable... When hurricanes hit the Texas Gulf Coast, all but radio communications can be lost between Brownsville, Texas to Houston, Texas. The weather stations there may have their eather radars operational but unable to send the picture or data to other weather stations. A highspeed, error free, robust, realtime, HF data mode is needed. The radar information may be 7.50 K bytes or larger. This data would need to be repeated every 5-10 minutes during critial stages of a hurricane. Walt/K5YFW Bill Aycock - W4BSG Woodville, Alabama 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! Groups Links 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! Groups Links Bill Aycock - W4BSG Woodville, Alabama 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! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/digitalradio/ * Your email settings: Individual Email | Traditional * To change settings online go to: http://groups.yahoo.com/group/digitalradio/join (Yahoo! ID required) * To change settings via email: mailto:[EMAIL PROTECTED] mailto:[EMAIL PROTECTED] * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
Re: [digitalradio] 16QPSK Modulation and Baud
--- KV9U [EMAIL PROTECTED] wrote: Walt, Maybe someone can clear this up, but what is the difference between the differential modes such as DBPSK, DQPSK, 8DPSK, and 16DPSK such as used with Pactor 2 and modes such as 8QPSK, 16QPSK? Even when theory says that differential modes have a worse BER, seemingly they work better on ionospheric paths, as with a moving ionosphere, is difficult to maintain an absolute phase reference. With the former, it is my understanding that with a single tone, the binary form (DBPSK) gives you one bit/second, DQPSK two, 8DPSK three and 16DPSK four. Still holds true... With the previous discussions on baud rate for the STANAG and MIL modems, can we still say that HF should use baud rates below 45? Depending on multipath, which is worse on lower frequencies. The claim is that these modems appear to be able to use extremely high baud rates, well above even 300 baud on HF and still work well under difficult conditions. The game is using many slow channels in parallel. Already in 1991 there was a 41 parallel tone modem being tested in transatlantic paths...it was capable of running 4800 bit per second and sometimes, up to 9600. In fact, the ALE folks believe that amateur radio is being held back on HF because we can not transmit in excess of 300 baud on most HF frequencies. Signalling ratethe speed at which every tone is wiggled. Actually, the ionosphere imposes a much lower rate for succesful transmission on the lower frequencies. Even Pactor does not exceed 200 baud and that is only under the best of conditions and even at 100 baud, the claim by Dr. Rink was that The short term time jitter has a magnitude of up to 5 msec. Larger time smearing can only be observed under very special conditions of the ionosphere. A baud rate of 100 symbols per second has proven to be low enough for almost all possible propagation conditions, especially if powerful error control coding is applied. Is there anyone here who can further explain this? Once againPactor can adaptively switch from 100 to 200 baud and back...be either Pactor I, II or III. Additionally, it can adaptively switch in and out constellation complexity and quantity of tones. Using compression, FEC and the whole boxful of coding tricks, it can go up to 5200 bits per second. I have seen it on Pactor III ocassionally running up to 3600 bps on 40 meters, and more often, 2800 and 1400 bps. 73 de Jose, CO2JA __ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com 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! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/digitalradio/ * Your email settings: Individual Email | Traditional * To change settings online go to: http://groups.yahoo.com/group/digitalradio/join (Yahoo! ID required) * To change settings via email: mailto:[EMAIL PROTECTED] mailto:[EMAIL PROTECTED] * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
RE: [digitalradio] 16QPSK Modulation and Baud
Ok Jose and everyone...let's take a poll or have some SWAGs. So what do YOU (plural) think is the best modulation technique to use for a NEW and BETTER HF data mode? PSK QPSK DBPSK DQPSK (Dairy Queen PSK...Dairy Queen is an ice cream franchise) 8DPSK DQPSK 8QPSK 16QPSK And by the way, the Russians have a 96 tone HF data mode that is suppose to have great throughput, is very robust and is wider than 4 KHz. Concerning baud... If the MUF is 32 MHz, then I believe that it is reasonable to think that 300 or 400 baud might work well on 10M...but on 40M and 80M it flat won't work. So at 40 and 80M we will probably find that 45.5 baud works rather well. Some might suggest that 31 baud is better. I don't know how we can really find out what baud is best for each band and even if we want to. Maybe we want to take a SWAG and have a different baud for every band? That's probably a bad idea. But what about 31 or 45 baud for 80-20M, 90 baud for 30M-15M and 200 baud for higher bands...we can make the baud rate manual or automatically selectable. For a basic or start, I would recommend manually selecting baud rates. My gut feeling is to start slow...play it safe to start with...31 or 45 baud all bands. Choose a good modulation technique...one that where you can manage the detection. Choose a method of FEC and add ARQ. You can see if you get better quality (error free copy) with or without ARQ, with or with FEC, etc. Choose a standard test text for testing and of course make sure that the chat mode works because after all, we DO (at least most hams) like to chat at bit. The KEY to any adventure is to have a goal and the flexibility to make changes as you go and work with as many as you can to evaluate what you create. Once a mode have shown what it can do, i.e. established its capability, then change to some other configuration. AND REMEMBER, IT NOT A BAD THING TO FAST FAIL A BAD IDEA. If something doesn't work as good as you have, deep six it...don't carry on with a bad idea. Its not a bad thing to say that you idea didn't work. Those who are very technically astute, you will have to being things such as throughput, and robustness, etc. down to terms that everyone can relate to. How about it? Are we (hams), as a group, up to creating a better communications mode? I know we can. 73, Walt/K5YFW -Original Message- From: digitalradio@yahoogroups.com [mailto:[EMAIL PROTECTED] Sent: Monday, September 18, 2006 8:28 AM To: digitalradio@yahoogroups.com Subject: Re: [digitalradio] 16QPSK Modulation and Baud --- KV9U [EMAIL PROTECTED] wrote: Walt, Maybe someone can clear this up, but what is the difference between the differential modes such as DBPSK, DQPSK, 8DPSK, and 16DPSK such as used with Pactor 2 and modes such as 8QPSK, 16QPSK? Even when theory says that differential modes have a worse BER, seemingly they work better on ionospheric paths, as with a moving ionosphere, is difficult to maintain an absolute phase reference. With the former, it is my understanding that with a single tone, the binary form (DBPSK) gives you one bit/second, DQPSK two, 8DPSK three and 16DPSK four. Still holds true... With the previous discussions on baud rate for the STANAG and MIL modems, can we still say that HF should use baud rates below 45? Depending on multipath, which is worse on lower frequencies. The claim is that these modems appear to be able to use extremely high baud rates, well above even 300 baud on HF and still work well under difficult conditions. The game is using many slow channels in parallel. Already in 1991 there was a 41 parallel tone modem being tested in transatlantic paths...it was capable of running 4800 bit per second and sometimes, up to 9600. In fact, the ALE folks believe that amateur radio is being held back on HF because we can not transmit in excess of 300 baud on most HF frequencies. Signalling ratethe speed at which every tone is wiggled. Actually, the ionosphere imposes a much lower rate for succesful transmission on the lower frequencies. Even Pactor does not exceed 200 baud and that is only under the best of conditions and even at 100 baud, the claim by Dr. Rink was that The short term time jitter has a magnitude of up to 5 msec. Larger time smearing can only be observed under very special conditions of the ionosphere. A baud rate of 100 symbols per second has proven to be low enough for almost all possible propagation conditions, especially if powerful error control coding is applied. Is there anyone here who can further explain this? Once againPactor can adaptively switch from 100 to 200 baud and back...be either Pactor I, II or III. Additionally, it can adaptively switch in and out constellation complexity and quantity of tones. Using compression, FEC and the whole boxful of coding tricks, it can go up to 5200 bits per second. I have seen it on Pactor III ocassionally
Re: [digitalradio] 16QPSK Modulation and Baud
Thanks for your comments, Jose, however, I think most of us understand and agree with what you say. What I am not clear on is the difference betwee the differential versions of the PSK modes and the non-differential versions. For example, my understanding is that PSK31 is really DBPSK31. I think perhaps QPSK is DQPSK? Are there cases where QPSK and higher order modulation does not use the differential form? Is the multitone modem using 41 parallel tones similar to the MIL/STANAG modems? Do you consider the STANAG modems running at multithousand baud rates as described by some of the ALE folks? Or is this a case where there is a difference of the definition? You can get very high bit rates from using multiple tones and with higher order modulations schemes such as what Pactor uses. But the claim by the ALE proponents is that we need much higher baud rates than only 300 baud in order to use the STANAG type modems because they run at speeds that exceed 1000 baud or more and are successfully used on HF. Presumably on the lower bands as well as the upper HF bands. Can you or anyone explain why they need this high speed on HF when even 300 baud is pushing the limit on the higher HF bands? 73, Rick, KV9U Already in 1991 there was a 41 parallel tone modem being tested in transatlantic paths...it was capable of running 4800 bit per second and sometimes, up to 9600. Jose Amador wrote: --- KV9U [EMAIL PROTECTED] wrote: Walt, Maybe someone can clear this up, but what is the difference between the differential modes such as DBPSK, DQPSK, 8DPSK, and 16DPSK such as used with Pactor 2 and modes such as 8QPSK, 16QPSK? Even when theory says that differential modes have a worse BER, seemingly they work better on ionospheric paths, as with a moving ionosphere, is difficult to maintain an absolute phase reference. With the former, it is my understanding that with a single tone, the binary form (DBPSK) gives you one bit/second, DQPSK two, 8DPSK three and 16DPSK four. Still holds true... With the previous discussions on baud rate for the STANAG and MIL modems, can we still say that HF should use baud rates below 45? Depending on multipath, which is worse on lower frequencies. The claim is that these modems appear to be able to use extremely high baud rates, well above even 300 baud on HF and still work well under difficult conditions. The game is using many slow channels in parallel. Already in 1991 there was a 41 parallel tone modem being tested in transatlantic paths...it was capable of running 4800 bit per second and sometimes, up to 9600. In fact, the ALE folks believe that amateur radio is being held back on HF because we can not transmit in excess of 300 baud on most HF frequencies. Signalling ratethe speed at which every tone is wiggled. Actually, the ionosphere imposes a much lower rate for succesful transmission on the lower frequencies. Even Pactor does not exceed 200 baud and that is only under the best of conditions and even at 100 baud, the claim by Dr. Rink was that The short term time jitter has a magnitude of up to 5 msec. Larger time smearing can only be observed under very special conditions of the ionosphere. A baud rate of 100 symbols per second has proven to be low enough for almost all possible propagation conditions, especially if powerful error control coding is applied. Is there anyone here who can further explain this? Once againPactor can adaptively switch from 100 to 200 baud and back...be either Pactor I, II or III. Additionally, it can adaptively switch in and out constellation complexity and quantity of tones. Using compression, FEC and the whole boxful of coding tricks, it can go up to 5200 bits per second. I have seen it on Pactor III ocassionally running up to 3600 bps on 40 meters, and more often, 2800 and 1400 bps. 73 de Jose, CO2JA 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! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/digitalradio/ * Your email settings: Individual Email | Traditional * To change settings online go to: http://groups.yahoo.com/group/digitalradio/join (Yahoo! ID required) * To change settings via email: mailto:[EMAIL PROTECTED] mailto:[EMAIL PROTECTED] * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
Re: [digitalradio] 16QPSK Modulation and Baud
--- DuBose Walt Civ AETC CONS/LGCA [EMAIL PROTECTED] wrote: Greeings All, How hard is it to demodulate a 16QPSK as compaired to a 8QPSK signal. Demodulation...I think it is about the same. Carrier regeneration is a bit more complex. Decoding it is something else, but also doable. And I have forgotten but does a 16QPSK signal will allow for 6 bites per cycle? Four bits per symbol (constellation position). Looking back at some very old hand written notes I took at an HF conference at Scott AFB, IL where Collins-Rockwell, Magnavox and Harris Comm Gp were making presentations, they said that they all agreeded that 45 baud (maybe 45.5) should be the highest baud rate for the low end of the HF band and even though you could go higher closer to the MUF, if you needed a fixed buad rate, chose the one that was the lowest. Certainly... Close to the MUF allows fewer rays, hopefully only one ray to propagate, which eliminates ISI. But there is still ionospheric doppler and noise/QRM to damage your received signal. Thus, if you have a single tone/carrier with 16QPSK, modulates at 45 baud, 1) what would its bandwidth be and 2) what is the total bit rate for the signal? (I would give you my answer; but think I might be really wrong and you will question my math. Hi Hi.) Formulas are in Communications Systems, by Carlson et al (4th Edition). Maybe Digital Communications, by Bernard Sklar could help. Maybe taking a peek at Wikipedia could help. I do not remember the formulas in detail by heart... Making more complex constellations carries more price tags than you could think at first sight. First, a more complex constellation has more capacity, but beyond QPSK the distance between the constellation points gets smaller, and the BER for the same RECEIVED power gets worse (on a clean channel, say wire or microwave, leave alone a noise HF channel). Complex constellations should be meant for clean, non dispersive channels. You can get an idea by drawing circles around the canonical points of a constellation up to half the distance between them. As long as signal plus noise falls within that circle, it MIGHT be identified correctly. Beyond that, confusion reigns... BPSK and QPSK have the same distance between constellation points, beyond that, distance begins to decrease, be it nPSK or mQAM. Second, you can get a better SNR to maintain the same BER using more power. And even when dB's are dB's, a 3 dB increase in power is not a thing to take too lightly (ask NASA Deep Space...). On HF you can only beat noise by increasing power...or using a better antenna...a hard feat to accomplish at those wavelengths. Have you ever seen a video presentation of a conference given by Doug Smith, KF6DX at the Georgia Tech about digital voice? There are two versions, the highest quality video tales some 100 MB. It is interesting, and deals with many aspects of digital voice, DSP, etc. I liked it a lot. Very practical, with solid theoretical foundations. And there you can see someting that separate the pros from the rest. IMD on your transmitter becomes another source of noise, as it creates distortion products that interfere with your PSK or QAM signal. What works on PSK31 (say, -20 dB on John Doe's japanese transceiver) would not work wel enough for a more complex constellation. 73 de Jose, CO2JA __ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com 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! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/digitalradio/ * Your email settings: Individual Email | Traditional * To change settings online go to: http://groups.yahoo.com/group/digitalradio/join (Yahoo! ID required) * To change settings via email: mailto:[EMAIL PROTECTED] mailto:[EMAIL PROTECTED] * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
Re: [digitalradio] 16QPSK Modulation and Baud
Walt, Maybe someone can clear this up, but what is the difference between the differential modes such as DBPSK, DQPSK, 8DPSK, and 16DPSK such as used with Pactor 2 and modes such as 8QPSK, 16QPSK? With the former, it is my understanding that with a single tone, the binary form (DBPSK) gives you one bit/second, DQPSK two, 8DPSK three and 16DPSK four. With the previous discussions on baud rate for the STANAG and MIL modems, can we still say that HF should use baud rates below 45? The claim is that these modems appear to be able to use extremely high baud rates, well above even 300 baud on HF and still work well under difficult conditions. In fact, the ALE folks believe that amateur radio is being held back on HF because we can not transmit in excess of 300 baud on most HF frequencies. Even Pactor does not exceed 200 baud and that is only under the best of conditions and even at 100 baud, the claim by Dr. Rink was that The short term time jitter has a magnitude of up to 5 msec. Larger time smearing can only be observed under very special conditions of the ionosphere. A baud rate of 100 symbols per second has proven to be low enough for almost all possible propagation conditions, especially if powerful error control coding is applied. Is there anyone here who can further explain this? 73, Rick, KV9U DuBose Walt Civ AETC CONS/LGCA wrote: Greeings All, How hard is it to demodulate a 16QPSK as compaired to a 8QPSK signal. And I have forgotten but does a 16QPSK signal will allow for 6 bites per cycle? Looking back at some very old hand written notes I took at an HF conference at Scott AFB, IL where Collins-Rockwell, Magnavox and Harris Comm Gp were making presentations, they said that they all agreeded that 45 baud (maybe 45.5) should be the highest baud rate for the low end of the HF band and even though you could go higher closer to the MUF, if you needed a fixed buad rate, chose the one that was the lowest. Thus, if you have a single tone/carrier with 16QPSK, modulates at 45 baud, 1) what would its bandwidth be and 2) what is the total bit rate for the signal? (I would give you my answer; but think I might be really wrong and you will question my math. Hi Hi.) Until tomorrow...Thanks and 73, Walt/K5YFW 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! Groups Links 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! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/digitalradio/ * Your email settings: Individual Email | Traditional * To change settings online go to: http://groups.yahoo.com/group/digitalradio/join (Yahoo! ID required) * To change settings via email: mailto:[EMAIL PROTECTED] mailto:[EMAIL PROTECTED] * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
