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PSK baud rates on HF
Recently I have heard references from multiple sources about 9.6kb PSK
activity on HF bands. What's the deal on this? Is it a wide, multi-stream mode like Q15x25 mode? It sounds illegal, but lots of things sound illegal if you are not familiar with the facts. That's me... I am not knowlegable about PSK packet. I do have a "flexible" modem though, that will allow me to operate PSK packet at a variety of baud rates... Isn't 1200 baud the limit on 10 meters, and 300 baud lower down? Somebody straighten me out on this, please... I'm cornfused. Charles Brabham, N5PVL Director: USPacket.Net http://www.uspacket.net |
On Fri, 28 Nov 2003 03:26:01 GMT, "charlesb"
wrote: Recently I have heard references from multiple sources about 9.6kb PSK activity on HF bands. I assume this refers to 9600 bit/s. What's the deal on this? Is it a wide, multi-stream mode like Q15x25 mode? It sounds illegal, but lots of things sound illegal if you are not familiar with the facts. That's me... A 9600 bit/s QPSK signal fits nicely within the same bandwidth occupied by an AM phone transmission, with 8PSK (or 8QAM) the signal would fit into the bandwidth of SSB phone transmissions. If the bandwidth limit allows AM or SSB, then what is the problem with other modes with similar bandwidths ? I am not knowlegable about PSK packet. I do have a "flexible" modem though, that will allow me to operate PSK packet at a variety of baud rates... Isn't 1200 baud the limit on 10 meters, and 300 baud lower down? That is a purely US specific issue. Anyway, 1200 baud or 1200 symbols/s is quite capable of transmitting 9600 bit/s provided that the SNR is good. It requires that 8 bits are transmitted within each symbol, i.e. each symbol can have 256 distinct states. While 256PSK would hardly be practical, 256QAM might work with high SNR and low phase distortion line of sight paths. 256QAM requires that the receiver must be able to detect more than 20 distinct states in both I and Q direction, thus quite small errors will spoil the reception. However 64QAM (6 bits/symbol) are widely used in Europe on the COFDM subcarriers used in digital television. Paul OH3LWR |
On Fri, 28 Nov 2003 03:26:01 GMT, "charlesb"
wrote: Recently I have heard references from multiple sources about 9.6kb PSK activity on HF bands. I assume this refers to 9600 bit/s. What's the deal on this? Is it a wide, multi-stream mode like Q15x25 mode? It sounds illegal, but lots of things sound illegal if you are not familiar with the facts. That's me... A 9600 bit/s QPSK signal fits nicely within the same bandwidth occupied by an AM phone transmission, with 8PSK (or 8QAM) the signal would fit into the bandwidth of SSB phone transmissions. If the bandwidth limit allows AM or SSB, then what is the problem with other modes with similar bandwidths ? I am not knowlegable about PSK packet. I do have a "flexible" modem though, that will allow me to operate PSK packet at a variety of baud rates... Isn't 1200 baud the limit on 10 meters, and 300 baud lower down? That is a purely US specific issue. Anyway, 1200 baud or 1200 symbols/s is quite capable of transmitting 9600 bit/s provided that the SNR is good. It requires that 8 bits are transmitted within each symbol, i.e. each symbol can have 256 distinct states. While 256PSK would hardly be practical, 256QAM might work with high SNR and low phase distortion line of sight paths. 256QAM requires that the receiver must be able to detect more than 20 distinct states in both I and Q direction, thus quite small errors will spoil the reception. However 64QAM (6 bits/symbol) are widely used in Europe on the COFDM subcarriers used in digital television. Paul OH3LWR |
"Paul Keinanen" wrote in message ... On Fri, 28 Nov 2003 03:26:01 GMT, "charlesb" wrote: Recently I have heard references from multiple sources about 9.6kb PSK activity on HF bands. I assume this refers to 9600 bit/s. What's the deal on this? Is it a wide, multi-stream mode like Q15x25 mode? It sounds illegal, but lots of things sound illegal if you are not familiar with the facts. That's me... A 9600 bit/s QPSK signal fits nicely within the same bandwidth occupied by an AM phone transmission, with 8PSK (or 8QAM) the signal would fit into the bandwidth of SSB phone transmissions. If the bandwidth limit allows AM or SSB, then what is the problem with other modes with similar bandwidths ? Well except that for standard PSK enthusiasts tout it's exceptionally narrow bandwidth thus allowing more conversations in a given space than even CW. What point is there in creating a wide digital mode? Dee D. Flint, N8UZE |
"Paul Keinanen" wrote in message ... On Fri, 28 Nov 2003 03:26:01 GMT, "charlesb" wrote: Recently I have heard references from multiple sources about 9.6kb PSK activity on HF bands. I assume this refers to 9600 bit/s. What's the deal on this? Is it a wide, multi-stream mode like Q15x25 mode? It sounds illegal, but lots of things sound illegal if you are not familiar with the facts. That's me... A 9600 bit/s QPSK signal fits nicely within the same bandwidth occupied by an AM phone transmission, with 8PSK (or 8QAM) the signal would fit into the bandwidth of SSB phone transmissions. If the bandwidth limit allows AM or SSB, then what is the problem with other modes with similar bandwidths ? Well except that for standard PSK enthusiasts tout it's exceptionally narrow bandwidth thus allowing more conversations in a given space than even CW. What point is there in creating a wide digital mode? Dee D. Flint, N8UZE |
"charlesb" wrote
Isn't 1200 baud the limit on 10 meters, and 300 baud lower down? This is a common misconception about baud and bits. You are correct about the baud rate limitations, although the baud rate is what is known legaly as the symbol rate. Suppose I design a modem that operates at 50 baud (20 ms symbol rate), obviously I can use this below 10 meters. Now, let's say I modulate that rate with 36 carriers of DQPSK. That is, there are 36 carriers of four phases (two bits per carrier), or 72 bits in 20 ms (50 baud). There's fifty 20 ms periods in a second, so we have (72 bits x 50), or 3600 bps. Now obviously we have learned something in the last 20 years, and that is, that HF is a bad medium, and you can either retry your transmissions until the band quits, or you can insert some sort of error correction into the transmission, to prevent retransmission. So let's say we limit the information to 2400 bps and insert 1200 bps of error correction (FEC), for a total of 3600 bps. Suppose each of the 36 carriers is a multiple of 62.5 Hz, then we can say that 62.5 x 36 is 2250 Hz. But we don't really want to go all the way down to 0 Hz, so let's say we start at 312 Hz (62.5 x 5) and this will push the right side out to (62.5 x (5 + 35)) or 2500 Hz. In summary, 36 carriers takes a lot of bandwidth, but no more than a standard analog sideband. The fact that you can fit 2400 bps voice, data, and image into the channel might be worth the complexity. P.S. I just described the G4GUO modem :-) |
"charlesb" wrote
Isn't 1200 baud the limit on 10 meters, and 300 baud lower down? This is a common misconception about baud and bits. You are correct about the baud rate limitations, although the baud rate is what is known legaly as the symbol rate. Suppose I design a modem that operates at 50 baud (20 ms symbol rate), obviously I can use this below 10 meters. Now, let's say I modulate that rate with 36 carriers of DQPSK. That is, there are 36 carriers of four phases (two bits per carrier), or 72 bits in 20 ms (50 baud). There's fifty 20 ms periods in a second, so we have (72 bits x 50), or 3600 bps. Now obviously we have learned something in the last 20 years, and that is, that HF is a bad medium, and you can either retry your transmissions until the band quits, or you can insert some sort of error correction into the transmission, to prevent retransmission. So let's say we limit the information to 2400 bps and insert 1200 bps of error correction (FEC), for a total of 3600 bps. Suppose each of the 36 carriers is a multiple of 62.5 Hz, then we can say that 62.5 x 36 is 2250 Hz. But we don't really want to go all the way down to 0 Hz, so let's say we start at 312 Hz (62.5 x 5) and this will push the right side out to (62.5 x (5 + 35)) or 2500 Hz. In summary, 36 carriers takes a lot of bandwidth, but no more than a standard analog sideband. The fact that you can fit 2400 bps voice, data, and image into the channel might be worth the complexity. P.S. I just described the G4GUO modem :-) |
"Dee D. Flint" wrote
Well except that for standard PSK enthusiasts tout it's exceptionally narrow bandwidth thus allowing more conversations in a given space than even CW. What point is there in creating a wide digital mode? Dee D. Flint, N8UZE Single channel PSK has nothing in common with high bandwidth information transport. What one group touts may be exactly opposite of what another group touts. Sometimes 31 bps at 31 baud is good enough, other times 3600 bps at 50 baud is what is needed. The point in creating a wide digital mode, is to increase throughput per second. |
"Dee D. Flint" wrote
Well except that for standard PSK enthusiasts tout it's exceptionally narrow bandwidth thus allowing more conversations in a given space than even CW. What point is there in creating a wide digital mode? Dee D. Flint, N8UZE Single channel PSK has nothing in common with high bandwidth information transport. What one group touts may be exactly opposite of what another group touts. Sometimes 31 bps at 31 baud is good enough, other times 3600 bps at 50 baud is what is needed. The point in creating a wide digital mode, is to increase throughput per second. |
"Dee D. Flint" wrote in message gy.com... What point is there in creating a wide digital mode? More throughput, error correction for 100% copy, ability to transfer binary files. ( Q15x25 guys like to send JPEG's back 'n forth, kind of like SSTV, except the pics come through 100% good. ) Obviously any wide mode is overkill for keyboard QSO's, but there's a whole world of other things that hams want or need to do, and some of them require more bandwidth. There are a lot of pro's and cons related to utilizing the wide modes for any purpose. I don't think we will have to worry about them becoming so popular that they will squeeze out everybody else. Charles Brabham, N5PVL Director: USPacket.Net http://www.uspacket.net |
"Dee D. Flint" wrote in message gy.com... What point is there in creating a wide digital mode? More throughput, error correction for 100% copy, ability to transfer binary files. ( Q15x25 guys like to send JPEG's back 'n forth, kind of like SSTV, except the pics come through 100% good. ) Obviously any wide mode is overkill for keyboard QSO's, but there's a whole world of other things that hams want or need to do, and some of them require more bandwidth. There are a lot of pro's and cons related to utilizing the wide modes for any purpose. I don't think we will have to worry about them becoming so popular that they will squeeze out everybody else. Charles Brabham, N5PVL Director: USPacket.Net http://www.uspacket.net |
"charlesb" wrote in message . com... More throughput, error correction for 100% copy, ability to transfer binary files. ( Q15x25 guys like to send JPEG's back 'n forth, kind of like SSTV, except the pics come through 100% good. ) Charles Brabham, N5PVL Director: USPacket.Net http://www.uspacket.net Where are the Q15x25 QSOs going on. I have MixW, which should work this mode, but I am not aware of ever hearing it on the HF bands. Is this a VHF/UHF only mode? 73 - Mike - K9JRI |
"charlesb" wrote in message . com... More throughput, error correction for 100% copy, ability to transfer binary files. ( Q15x25 guys like to send JPEG's back 'n forth, kind of like SSTV, except the pics come through 100% good. ) Charles Brabham, N5PVL Director: USPacket.Net http://www.uspacket.net Where are the Q15x25 QSOs going on. I have MixW, which should work this mode, but I am not aware of ever hearing it on the HF bands. Is this a VHF/UHF only mode? 73 - Mike - K9JRI |
"Mike Blake" wrote in message gy.com... Where are the Q15x25 QSOs going on. I have MixW, which should work this mode, but I am not aware of ever hearing it on the HF bands. Is this a VHF/UHF only mode? It's intended for HF, but works great on VHF/UHF too. Operating freqs listed in the pages that follow. http://home.att.net/~ronchap/q15x25modes/q15x25.htm http://sharon.pi8zaa.ampr.org/mirror...25/Q15X25.html There is also a Yahoo group named "Q15x25" that is a great source of info on operating this digital mode. Briefly: Q15x25 uses 15 PSK streams at 88.xxx baud each, theoretically giving you around 2500 baud. That's where the 15 and 25 in the name come from. It butts right up against the legal limits of bandwidth, but doesn't cross those limits and is so it legal, despite doubts that some have expressed in the past. Q15x25 operates exactly like packet. It's a connected mode, and if a frame gets through at all, it gets through intact. From what I can tell, the most popular activity among Q15x25 enthusiasts is to swap JPEG images on the air, kind of like SSTV but with error-correction so the pics always come through clean. There are versions for Linux and Winders. My on the air experience with Q15x25 is that it works great when you have clear spectrum, but under noisy conditions is no better or worse than 300 baud packet! - Except of course it takes up several times as much spectrum to do so. Q15x25 will not pull out weak signals you can't hear or any of that kind of stuff. On the other hand, under decent operating conditions it can be pretty fast. I also have discovered that by boosting the TXD up to 800-1000 MS or more, you can conduct Q15x25 QSO's over a normal VHF voice repeater. A nice 2500 baud data transfer system for emergency use anywhere there is a voice repeater... Admittedly not ideal, but still a big step up from nothing. I remember reading a few weeks back that the author/authors of Q15x25 were currently working on a new version, so it appears the mode is alive and well, if not popular due to it's width. It really is hard to find a good place to operate Q15x25 on busy freqs. That's the problem with the wide modes, I guess. TANSTAAFL Charles Brabham, N5PVL Director: USPacket.Net http://www.uspacket.net |
"Mike Blake" wrote in message gy.com... Where are the Q15x25 QSOs going on. I have MixW, which should work this mode, but I am not aware of ever hearing it on the HF bands. Is this a VHF/UHF only mode? It's intended for HF, but works great on VHF/UHF too. Operating freqs listed in the pages that follow. http://home.att.net/~ronchap/q15x25modes/q15x25.htm http://sharon.pi8zaa.ampr.org/mirror...25/Q15X25.html There is also a Yahoo group named "Q15x25" that is a great source of info on operating this digital mode. Briefly: Q15x25 uses 15 PSK streams at 88.xxx baud each, theoretically giving you around 2500 baud. That's where the 15 and 25 in the name come from. It butts right up against the legal limits of bandwidth, but doesn't cross those limits and is so it legal, despite doubts that some have expressed in the past. Q15x25 operates exactly like packet. It's a connected mode, and if a frame gets through at all, it gets through intact. From what I can tell, the most popular activity among Q15x25 enthusiasts is to swap JPEG images on the air, kind of like SSTV but with error-correction so the pics always come through clean. There are versions for Linux and Winders. My on the air experience with Q15x25 is that it works great when you have clear spectrum, but under noisy conditions is no better or worse than 300 baud packet! - Except of course it takes up several times as much spectrum to do so. Q15x25 will not pull out weak signals you can't hear or any of that kind of stuff. On the other hand, under decent operating conditions it can be pretty fast. I also have discovered that by boosting the TXD up to 800-1000 MS or more, you can conduct Q15x25 QSO's over a normal VHF voice repeater. A nice 2500 baud data transfer system for emergency use anywhere there is a voice repeater... Admittedly not ideal, but still a big step up from nothing. I remember reading a few weeks back that the author/authors of Q15x25 were currently working on a new version, so it appears the mode is alive and well, if not popular due to it's width. It really is hard to find a good place to operate Q15x25 on busy freqs. That's the problem with the wide modes, I guess. TANSTAAFL Charles Brabham, N5PVL Director: USPacket.Net http://www.uspacket.net |
G'day Guys!
Came across your thread and just thought I would give you all some great news about Q15X25! Currently there is finally firmware being developed for the Kam XL Dual port DSP TNC range!. This is great news for those who don't wish to rely on PC / Sound Card hardware to run this mode, finally there will be a small black box solution!. Regards, Ken. VK4AKP. .-.-. |
VK4AKP writes:
Currently there is finally firmware being developed for the Kam XL Dual port DSP TNC range!. This is great news for those who don't wish to rely on PC / Sound Card hardware to run this mode, finally there will be a small black box solution!. Cool. I wonder why nobody builds this stuff directly into radio tranceivers. What I really want is a portable PSK31 tranceiver with an alphanumeric keypad, 4 line (or so) LCD text display, AA battery pack, all the PSK31 modulation/demodulation stuff, and all the RF stuff in a single box, no computer needed. I'm imagining something about the size of an FT817 and reasonably rugged. It could be single band, like 20 meters, and it would of course have a computer port for when a computer was available. That would be a way to have fairly reliable DX portable communications without resorting to satellites. I wonder why nobody makes anything like this, or builds the feature into FT817-class radios. I'm sure there'd be demand for it. |
In article ,
Paul Rubin wrote: Cool. I wonder why nobody builds this stuff directly into radio tranceivers. For one thing, the market for digital modes is so small compared with the market for voice operation. For another, the digital modes keep evolving rapidly, so it's a lot easier to use a PC to develop and distribute software than having it in some form that only works in a particular make and model transceiver. Seems like the transceiver makers are just now getting around to having the higher-end models able to decode and display RTTY. That isn't a feature I would pay for, because I do lots of digital modes, and because I would imagine those that run in a PC might do a better job of decoding than something built into the transceiver. The PC software gets lots of user experience and frequent updates until it is more or less optimized. You don't get that with something built into the transceiver. Not to say that you don't have a legitimate wish for a highly portable PSK station. Just that it is unlikely to happen in a commercial product. -- jhhaynes at earthlink dot net |
Hi Ken,
As soon as they have that Firmware available I will be getting one... Have been playing with MixW and Q15x25.... Nice.... I do like the TNc idea as well.. 73 jerry n9lya "VK4AKP" wrote in message ... G'day Guys! Came across your thread and just thought I would give you all some great news about Q15X25! Currently there is finally firmware being developed for the Kam XL Dual port DSP TNC range!. This is great news for those who don't wish to rely on PC / Sound Card hardware to run this mode, finally there will be a small black box solution!. Regards, Ken. VK4AKP. -.-. -- VK4AKP |
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