Re: [digitalradio] Has anyone looked into FPGA-based digital modes?
John B. Stephensen wrote: FPGAs are useful for signal processing as you can do many operations in parallel. FIR filter, FFT and CORDIC modules are available in the free development software from Xilinx. They are very good for processing wideband signals or digitizing an entire amateur band and then filtering the result. Unfortunately, the starter kit has only low-speed low-resolution ADCs and DACs. 73, John KD6OZH Speed and resolution are, of course, relative :) While those chips are capable of crunching on half the HF spectrum at once, I was thinking initially of just audio (for which the on-board converters would be fine) - kind of a super-TNC, with capabilities (speed/bandwidth) similar to Pactor-III with no patents, open-source software, and significantly lower hardware costs. Sound card modes, of course, have gained popularity due to their flexibility and low cost - but can't handle the tight timing needed for pactor-type modes. It just seemed to me that something like a commercially-available low-cost FPGA board might be able to get the best of both worlds. Yeah, I'm suggesting a minor paradigm shift. Scary. 73, Paul / K9PS
[digitalradio] RadioCom 6?
Anyone here using the RadioCom 6 software ?
Re: [digitalradio] Has anyone looked into FPGA-based digital modes?
Hi Paul, Sounds like you might be getting caught up with some of your other work and can devote some time again to digital modes:) For those who are not aware, it was Paul's paper on ARQ concepts that lead to development of several current uses of ham radio ARQ modes. Some comments and questions: 1. Years ago we had the outboard programmables but they never really were all that popular. I know of only one ham in our area (multi-county rural area) who had one. Can the paradigm be revived? I don't think it can for the average HF digital ham since they do not seem to have that much interest in ARQ modes. Most are quite happy to only use PSK31 and no other mode. When it doesn't work, they don't tend to switch to MFSK16 or Olivia. They just go and do something else. 2. Is it really true that computers (using a sound card) can not switch fast enough? When I toggle the PTT on my sound card modes, I can barely tell there is any delay in switching the rig. While I would not want to key CW that way, it seems plenty fast enough for reasonable switching speeds needed for an ARQ digital mode. Since we would not necessarily need to exactly duplicate Pactor modes, couldn't there just be a few extra milliseconds of padding to take care of differences in any delays depending upon the computer? Based on the timing for Pactor 2 and 3, do you still find that the average computer can not handle the window for the ARQ ACK/NAK response? 3. The SCAMP mode, developed by the Winlink 2000 group, proved conclusively that you don't even need such close timing anyway since you could do the decoding in the background (pipelining) during the time that the next packet was being sent. SCAMP worked fabulously well with good signals. If other slower protocols were used (but still keeping the 1000 wpm speed) it would work with much more difficult conditions. 4. Other than a few of us who have significant interest in public service/emergency communications and the need for absolute accuracy in messaging, there seems to be nearly no interest:( I wish it was not this way, but consider that the FAE400 mode, which is very sensitive, can work under fairly difficult conditions that would make PSK31 impossible, and has ARQ built in, is almost never used after a modest interest in testing it last year. 5. Therefore, it seems important to insure that there is a purpose for the development of a new ARQ mode to meet some unmet need. I might suggest that possible interest in having the capability to handle public service messaging, with total accuracy, and under conditions that may make CW difficult, and yet provide the access to automated e-mail that can also handle time shifting store and hold for later retrieval. As an example, there are probably a few of us who used to be active with CW/phone traffic handling a few decades ago, but who did not want to be forced to adhere to a specific schedule during non emergency times. Packet BBS systems had some of the paradigm but for decentralized systems did not work well on HF since the mode requires very good signals and throughput was often marginal to nil. A decentralized ad hoc, robust, low cost system that gave us a choice of routing e-mail or holding it for a local ham could be a new paradigm that enough radio amateurs might move toward. There is no other system that can do this now and nothing on the horizon. I would personally be interested in hosting such a system. Any other hams feel the same way? Or do you think such an approach would languish? 73, Rick, KV9U Paul L Schmidt, K9PS wrote: Speed and resolution are, of course, relative :) While those chips are capable of crunching on half the HF spectrum at once, I was thinking initially of just audio (for which the on-board converters would be fine) - kind of a super-TNC, with capabilities (speed/bandwidth) similar to Pactor-III with no patents, open-source software, and significantly lower hardware costs. Sound card modes, of course, have gained popularity due to their flexibility and low cost - but can't handle the tight timing needed for pactor-type modes. It just seemed to me that something like a commercially-available low-cost FPGA board might be able to get the best of both worlds. Yeah, I'm suggesting a minor paradigm shift. Scary. 73, Paul / K9PS
Re: [digitalradio] Has anyone looked into FPGA-based digital modes?
where could one finds these modes MATTHEW A. GREGORY KC2PUA - Original Message From: Rick W. [EMAIL PROTECTED] To: digitalradio@yahoogroups.com Sent: Sunday, August 3, 2008 11:46:11 AM Subject: Re: [digitalradio] Has anyone looked into FPGA-based digital modes? Hi Paul, Sounds like you might be getting caught up with some of your other work and can devote some time again to digital modes:) For those who are not aware, it was Paul's paper on ARQ concepts that lead to development of several current uses of ham radio ARQ modes. Some comments and questions: 1. Years ago we had the outboard programmables but they never really were all that popular. I know of only one ham in our area (multi-county rural area) who had one. Can the paradigm be revived? I don't think it can for the average HF digital ham since they do not seem to have that much interest in ARQ modes. Most are quite happy to only use PSK31 and no other mode. When it doesn't work, they don't tend to switch to MFSK16 or Olivia. They just go and do something else. 2. Is it really true that computers (using a sound card) can not switch fast enough? When I toggle the PTT on my sound card modes, I can barely tell there is any delay in switching the rig. While I would not want to key CW that way, it seems plenty fast enough for reasonable switching speeds needed for an ARQ digital mode. Since we would not necessarily need to exactly duplicate Pactor modes, couldn't there just be a few extra milliseconds of padding to take care of differences in any delays depending upon the computer? Based on the timing for Pactor 2 and 3, do you still find that the average computer can not handle the window for the ARQ ACK/NAK response? 3. The SCAMP mode, developed by the Winlink 2000 group, proved conclusively that you don't even need such close timing anyway since you could do the decoding in the background (pipelining) during the time that the next packet was being sent. SCAMP worked fabulously well with good signals. If other slower protocols were used (but still keeping the 1000 wpm speed) it would work with much more difficult conditions. 4. Other than a few of us who have significant interest in public service/emergency communications and the need for absolute accuracy in messaging, there seems to be nearly no interest:( I wish it was not this way, but consider that the FAE400 mode, which is very sensitive, can work under fairly difficult conditions that would make PSK31 impossible, and has ARQ built in, is almost never used after a modest interest in testing it last year. 5. Therefore, it seems important to insure that there is a purpose for the development of a new ARQ mode to meet some unmet need. I might suggest that possible interest in having the capability to handle public service messaging, with total accuracy, and under conditions that may make CW difficult, and yet provide the access to automated e-mail that can also handle time shifting store and hold for later retrieval. As an example, there are probably a few of us who used to be active with CW/phone traffic handling a few decades ago, but who did not want to be forced to adhere to a specific schedule during non emergency times. Packet BBS systems had some of the paradigm but for decentralized systems did not work well on HF since the mode requires very good signals and throughput was often marginal to nil. A decentralized ad hoc, robust, low cost system that gave us a choice of routing e-mail or holding it for a local ham could be a new paradigm that enough radio amateurs might move toward. There is no other system that can do this now and nothing on the horizon. I would personally be interested in hosting such a system. Any other hams feel the same way? Or do you think such an approach would languish? 73, Rick, KV9U Paul L Schmidt, K9PS wrote: Speed and resolution are, of course, relative :) While those chips are capable of crunching on half the HF spectrum at once, I was thinking initially of just audio (for which the on-board converters would be fine) - kind of a super-TNC, with capabilities (speed/bandwidth) similar to Pactor-III with no patents, open-source software, and significantly lower hardware costs. Sound card modes, of course, have gained popularity due to their flexibility and low cost - but can't handle the tight timing needed for pactor-type modes. It just seemed to me that something like a commercially- available low-cost FPGA board might be able to get the best of both worlds. Yeah, I'm suggesting a minor paradigm shift. Scary. 73, Paul / K9PS
Re: [digitalradio] Has anyone looked into FPGA-based digital modes?
Hi Matt, For the ARQ modes, the main one that works with the weaker signals is FAE400 and is only found in the Multipsk program invented by Patrick, F6CTE. He took the 8FSK 125 baud waveform from the old MIL-STD-188-141A ALE protocol and slowed the speed down to 50 baud, then added compression, and amazingly added memory ARQ, similar to what Pactor does and what others have said for years could never be done. The performance is dramatically improved over the 141A protocol and is competitive with other non-ARQ sound card modes. It is not quite as competitive as Olivia and MFSK modes, but then those modes are slower. http://f6cte.free.fr/index_anglais.htm - - - - - There are two other ARQ technologies that can work with weaker signals ... PSKmail and NBEMS. PSKmail runs only on Linux and is going nowhere here in the U.S. Perhaps better in some other countries? I am hopeful that it will catch on to a greater degree, but until a critical mass of hams adopt Linux here in the U.S. or PSKmail is developed for MS Windows (which the developer says will not happen), I don't see how it can become useful without enough available hams. My understanding is that PSKmail can also do peer to peer ARQ chat as well as automatic e-mailing. It can run on the Linux version of the EeePC for excellent portability. PSKmail uses various speeds of PSK, especially PSK63 and is designed primarily for HF use with the narrow modes. http://pskmail.wikispaces.com/ - - - - - NBEMS (Narrow Band Emergency Messaging System) is manually operated which requires operators at both ends. It allows for ARQ messages to be sent without error as files. It does not include peer to peer ARQ chat but can operate compatibly with non-ARQ chat modes such as PSK, MFSK, and even RTTY. w1hkj.com and http://w1hkj.com/NBEMS/index.html NBEMS is one of the only cross platform systems since it runs on Linux and MS Windows. It ARQ's the fldigi multimode software with flarq using fast light development. The Windows side currently uses VBdigi, but we have heard that Dave, W1HKJ, is working on a Windows version of fldigi. NBEMS can use several different sound card protocols, including PSK and MFSK and we have heard that they are developing a new mode(s)? for this system. It was initially developed primarily for VHF, but can be used on HF. - - - - - SCAMP (Sound Card Amateur Messaging Protocol) was developed several years ago by the Winlink 2000 software developer and was to be available as an alternative to the very expensive and single sourced proprietary SCS modem (~ $1000). I found the program to work extremely well when conditions were good (close to +10 dB S/N) since it had a top speed of close to 1000 wpm for the HF version. You had to see it in operation to see how powerful it was. But, as expected, using the RDFT protocol, it was not possible to handle even zero dB S/N signals, much less below zero dB as many improved sound card modes can do now. They discontinued all further development, but did say they were planning on making it available to the amateur community. As far as I was able to find out, they never did. not to do this. The only logical reason seems to me to prevent other hams from more easily developing systems that could compete with Winlink 2000. So with the new developments have been somewhat reinvention of the wheel:) The software had self destruct timers built in to insure that it could never be used after a few months and so is no longer available:( The higher speed version for VHF also did not appear to be developed further, however I only was involved with the HF side. Perhaps with the completion of major changes to the Winlink 2000 system, they will revisit further development? If you have any other questions please let us know. Often someone here has the information. 73, Rick, KV9U matt gregory wrote: where could one finds these modes MATTHEW A. GREGORY KC2PUA - Original Message From: Rick W. [EMAIL PROTECTED] To: digitalradio@yahoogroups.com Sent: Sunday, August 3, 2008 11:46:11 AM Subject: Re: [digitalradio] Has anyone looked into FPGA-based digital modes? Hi Paul, Sounds like you might be getting caught up with some of your other work and can devote some time again to digital modes:) For those who are not aware, it was Paul's paper on ARQ concepts that lead to development of several current uses of ham radio ARQ modes. Some comments and questions: 1. Years ago we had the outboard programmables but they never really were all that popular. I know of only one ham in our area (multi-county rural area) who had one. Can the paradigm be revived? I don't think it can for the average HF digital ham since they do not seem to have that much interest in ARQ modes. Most are quite happy to only use PSK31 and no other mode. When it doesn't work, they don't tend to switch to MFSK16 or Olivia. They just go and do something else. 2. Is it
[digitalradio] Re: Has anyone looked into FPGA-based digital modes?
To echo what Rick stated, FAE400 is an extremely useful ARQ mode that has a lot of potential; robust yet reasonably narrow. Works very well, just a shame so few use it. NBEMS is also a good ARQ suite, but a lot slower when using HF friendly modes. No sure the lock-up time using MFSK16 has been resolved but the new FLDIGI had the mode THOR, an incremental shift keying mode similar to DominoEX. Not sure if that will be implemented into NBEMS, although it certainly has that potential, especially as it retains DominoEx's tolerance to frequency accuracy. The ax25 packet structure was fine; problem was/is that ax25 at 300 Baud on HF, unless near MUF, is a less then optimum speed choice. It actually works fairly well at 110 Baud but it is slow. I think there are many good protocols out there, but not many want to experiment. 73, Bill N9DSJ --- In digitalradio@yahoogroups.com, Rick W. [EMAIL PROTECTED] wrote: Hi Matt, For the ARQ modes, the main one that works with the weaker signals is FAE400 and is only found in the Multipsk program invented by Patrick, F6CTE. He took the 8FSK 125 baud waveform from the old MIL-STD-188-141A ALE protocol and slowed the speed down to 50 baud, then added compression, and amazingly added memory ARQ, similar to what Pactor does and what others have said for years could never be done. The performance is dramatically improved over the 141A protocol and is competitive with other non-ARQ sound card modes. It is not quite as competitive as Olivia and MFSK modes, but then those modes are slower. http://f6cte.free.fr/index_anglais.htm - - - - - There are two other ARQ technologies that can work with weaker signals ... PSKmail and NBEMS. PSKmail runs only on Linux and is going nowhere here in the U.S. Perhaps better in some other countries? I am hopeful that it will catch on to a greater degree, but until a critical mass of hams adopt Linux here in the U.S. or PSKmail is developed for MS Windows (which the developer says will not happen), I don't see how it can become useful without enough available hams. My understanding is that PSKmail can also do peer to peer ARQ chat as well as automatic e-mailing. It can run on the Linux version of the EeePC for excellent portability. PSKmail uses various speeds of PSK, especially PSK63 and is designed primarily for HF use with the narrow modes. http://pskmail.wikispaces.com/ - - - - - NBEMS (Narrow Band Emergency Messaging System) is manually operated which requires operators at both ends. It allows for ARQ messages to be sent without error as files. It does not include peer to peer ARQ chat but can operate compatibly with non-ARQ chat modes such as PSK, MFSK, and even RTTY. w1hkj.com and http://w1hkj.com/NBEMS/index.html NBEMS is one of the only cross platform systems since it runs on Linux and MS Windows. It ARQ's the fldigi multimode software with flarq using fast light development. The Windows side currently uses VBdigi, but we have heard that Dave, W1HKJ, is working on a Windows version of fldigi. NBEMS can use several different sound card protocols, including PSK and MFSK and we have heard that they are developing a new mode(s)? for this system. It was initially developed primarily for VHF, but can be used on HF. - - - - - SCAMP (Sound Card Amateur Messaging Protocol) was developed several years ago by the Winlink 2000 software developer and was to be available as an alternative to the very expensive and single sourced proprietary SCS modem (~ $1000). I found the program to work extremely well when conditions were good (close to +10 dB S/N) since it had a top speed of close to 1000 wpm for the HF version. You had to see it in operation to see how powerful it was. But, as expected, using the RDFT protocol, it was not possible to handle even zero dB S/N signals, much less below zero dB as many improved sound card modes can do now. They discontinued all further development, but did say they were planning on making it available to the amateur community. As far as I was able to find out, they never did. not to do this. The only logical reason seems to me to prevent other hams from more easily developing systems that could compete with Winlink 2000. So with the new developments have been somewhat reinvention of the wheel:) The software had self destruct timers built in to insure that it could never be used after a few months and so is no longer available:( The higher speed version for VHF also did not appear to be developed further, however I only was involved with the HF side. Perhaps with the completion of major changes to the Winlink 2000 system, they will revisit further development? If you have any other questions please let us know. Often someone here has the information. 73, Rick, KV9U matt gregory wrote: where could one finds these modes MATTHEW A. GREGORY
Re: [digitalradio] Has anyone looked into FPGA-based digital modes?
Paul you just hit the nail right square on the head. I have said just that for years. Don't say that to long and loud. The anti-wide pople will come and get you. John At 08:27 AM 8/3/2008 -0400, you wrote in part: Sound card modes, of course, have gained popularity due to their flexibility and low cost - but can't handle the tight timing needed for pactor-type modes. Paul / K9PS
RE: [digitalradio] Re: Has anyone looked into FPGA-based digital modes?
AA6YQ comments below From: digitalradio@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Bill McLaughlin Sent: Sunday, August 03, 2008 5:02 PM To: digitalradio@yahoogroups.com Subject: [digitalradio] Re: Has anyone looked into FPGA-based digital modes? To echo what Rick stated, FAE400 is an extremely useful ARQ mode that has a lot of potential; robust yet reasonably narrow. Works very well, just a shame so few use it. With a 400 Hz bandwidth and no panoramic reception (I'm assuming - please correct me if I'm wrong), most ragchewers would consider this a step backwards despite its improved sensitivity and robustness. If 7O1DX were to show up on FAE400, however, DXers would adopt his mode in large numbers. One way to prime this pump would be to make it easier for existing digital mode applications to incorporate FAE400 support, as Peter G3PLX and Moe AE4JY did to accelerate soundcard PSK31 adoption. Arguably, digital mode protocols are subject to Metcalfe's law: the value of a http://en.wikipedia.org/wiki/Telecommunications_network telecommunications network is proportional to the square of the number of users of the system. Unless a new protocol is head-and-shoulders better than the incumbents, bootstrapping activities like this will be necessary. snip I think there are many good protocols out there, but not many want to experiment. As I have said here before, it is a mistake to blame the user community. Every op using PSK today gave it a first try at some point, and decided that they liked what they saw well enough to continue using it and to advocate its use to their friends. If you want users to give your new protocol a first try, then a. Differentiate it in a positive and significant way from current protocols (more reliable, less bandwidth, more sensitive, easier to use, new functionality, etc.) so that more users will be motivated to give it a try and become aficionados b. Make the modulator and demodulator available in a form easily incorporated into existing digital mode applications so that users need not abandon their familiar digital mode applications to try the new mode, and so that they will find plenty of QSO partners It is not as easy for a new protocol to cross the chasm from early adopters (e.g. most of the users in this forum) to broad-scale usage as it was back when PSK31 made this move, but I believe that opportunities remain; Rick's wistful description of SCAMP provides several tantalizing clues. 73, Dave, AA6YQ
Re: [digitalradio] Re: Has anyone looked into FPGA-based digital modes?
I believe that both the AX.25 and the BBS model are OK, but that the packet channel coding is a disaster in the sense that a single erroneous bit trashes a frame. That fires up the retries chain that are so detrimental to the link capacity, and may sever it as well. Pactor does a _LOT_ better, as it is able to use frames with errors that would be useless on packet using different FEC mechanisms. Source compression may help as well, as FBB and WL2K do. If the signalling speed can be made to match the channel and the protocol yield capabilities under a certain level of errors, a huge relative improvement can be achieved. That is the big adventage of WL2K, the use of Pactor II and its better channel coding. The rest is much alike the old BBS system, reworked. I believe that something that achieves similar results to those stated above will certainly be a step ahead. 73, Jose, CO2JA --- Bill McLaughlin wrote: To echo what Rick stated, FAE400 is an extremely useful ARQ mode that has a lot of potential; robust yet reasonably narrow. Works very well, just a shame so few use it. NBEMS is also a good ARQ suite, but a lot slower when using HF friendly modes. No sure the lock-up time using MFSK16 has been resolved but the new FLDIGI had the mode THOR, an incremental shift keying mode similar to DominoEX. Not sure if that will be implemented into NBEMS, although it certainly has that potential, especially as it retains DominoEx's tolerance to frequency accuracy. The ax25 packet structure was fine; problem was/is that ax25 at 300 Baud on HF, unless near MUF, is a less then optimum speed choice. It actually works fairly well at 110 Baud but it is slow. I think there are many good protocols out there, but not many want to experiment. 73, Bill N9DSJ
Re: [digitalradio] Re: Has anyone looked into FPGA-based digital modes?
I fully agree that just having a new mode that might be marginally better than a popular mode will have a difficult time competing. While most ragchewers would not necessarily need an ARQ mode, I personally prefer it. But I am in the extreme minority. I used to have Amtor contacts in old days with few errors until signals were getting to weak for Amtor to decode properly and you would start getting garbage characters. Several of the sound card modes of today are quite superior to Amtor when conditions drop off. If we want to have success with an ARQ mode, it needs to be used for purposes where ARQ is either desirable to have e.g., between two hams who want to chat error free under difficult conditions, or when it is absolutely necessary to have, e.g., when sending message traffic, especially for third parties where you have unknown data such as telephone numbers, address, etc. Another purpose would be to control a bbs system where the wrong commands are not. I don't see ARQ modes frequently used by hams calling CQ for a casual contact. The reason that this is not happening now, is at least partly that there is nothing that can do it well. Even if there was something in place, would it be used? There may be resistance from existing traffic handlers who want to keep the camaraderie going with phone/cw nets which I admit can be missing with digital networks unless you factor this into the equation. I certainly agree that developing engines that are transferable to other programs is necessary to have widespread use and Bob M's thoughts are probably quite true. One final comment on SCAMP. This mode was never made available to the amateur community so we can not know if anyone would have developed it further into a BBS or e-mail interface system that I would have liked to see. (With a fall back slower series of modes of course, to handle the more challenging conditions). I know that if we had such a system, I would be a user and likely also a server station. This needs to be a stand alone system that has alternatives available at different locations and can be reached with moderate power and antennas. 73, Rick, KV9U Dave AA6YQ wrote: With a 400 Hz bandwidth and no panoramic reception (I’m assuming – please correct me if I’m wrong), most ragchewers would consider this a step backwards despite its improved sensitivity and robustness. If 7O1DX were to show up on FAE400, however, DXers would adopt his mode in large numbers. One way to prime this pump would be to make it easier for existing digital mode applications to incorporate FAE400 support, as Peter G3PLX and Moe AE4JY did to accelerate soundcard PSK31 adoption. Arguably, digital mode protocols are subject to Metcalfe’s law: “the value of a telecommunications network http://en.wikipedia.org/wiki/Telecommunications_network is proportional to the square of the number of users of the system”. Unless a new protocol is head-and-shoulders better than the incumbents, bootstrapping activities like this will be necessary. As I have said here before, it is a mistake to blame the user community. Every op using PSK today gave it a first try at some point, and decided that they liked what they saw well enough to continue using it and to advocate its use to their friends. If you want users to give your new protocol a first try, then a. Differentiate it in a positive and significant way from current protocols (more reliable, less bandwidth, more sensitive, easier to use, new functionality, etc.) so that more users will be motivated to give it a try and become aficionados b. Make the modulator and demodulator available in a form easily incorporated into existing digital mode applications so that users need not abandon their familiar digital mode applications to try the new mode, and so that they will find plenty of QSO partners It is not as easy for a new protocol to “cross the chasm” from early adopters (e.g. most of the users in this forum) to broad-scale usage as it was back when PSK31 made this move, but I believe that opportunities remain; Rick’s wistful description of SCAMP provides several tantalizing clues… Announce your digital presence via our Interactive Sked Page at http://www.obriensweb.com/sked Check our other Yahoo Groups http://groups.yahoo.com/group/dxlist/ http://groups.yahoo.com/group/contesting http://groups.yahoo.com/group/themixwgroup 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
Re: [digitalradio] Has anyone looked into FPGA-based digital modes?
The ADC and DAC are certainly adequate for audio so it will work. I've been interested in VHF and UHF high-speed modems so I have a starter kit outfitted with a high-speed ADC and DAC that plug into J3. So far I've tested the DDS and am in the middle of testing the second version of a 16-bit soft MCU. After that, I have a lot of Verilog code imported from a Spartan-3 project and converted from ISE 7 to ISE 10 that needs to be integrated and tested. That should eventualy result in an OFDM modem that operates at up to 2 Mbps. Real-time signal processing is done in dedicated modules for filtering, FFT and CORDIC, but in this design the soft processor is to handle everything between the FFT and the Ethernet port. Think of it as an Intersil HSP50214 plus an FFT and MCU in one FPGA. The soft MCU would probably be enough to process 8 ksps audio for a modem as it has a MAC instruction. 3 or 4 would fit in an XC3S500E. 73, John KD6OZH - Original Message - From: Paul L Schmidt, K9PS To: digitalradio@yahoogroups.com Sent: Sunday, August 03, 2008 12:27 UTC Subject: Re: [digitalradio] Has anyone looked into FPGA-based digital modes? John B. Stephensen wrote: FPGAs are useful for signal processing as you can do many operations in parallel. FIR filter, FFT and CORDIC modules are available in the free development software from Xilinx. They are very good for processing wideband signals or digitizing an entire amateur band and then filtering the result. Unfortunately, the starter kit has only low-speed low-resolution ADCs and DACs. 73, John KD6OZH Speed and resolution are, of course, relative :) While those chips are capable of crunching on half the HF spectrum at once, I was thinking initially of just audio (for which the on-board converters would be fine) - kind of a super-TNC, with capabilities (speed/bandwidth) similar to Pactor-III with no patents, open-source software, and significantly lower hardware costs. Sound card modes, of course, have gained popularity due to their flexibility and low cost - but can't handle the tight timing needed for pactor-type modes. It just seemed to me that something like a commercially-available low-cost FPGA board might be able to get the best of both worlds. Yeah, I'm suggesting a minor paradigm shift. Scary. 73, Paul / K9PS
