Re: [digitalradio] Re: New emcomm tool now available
On 10/18/07, Andrew O'Brien [EMAIL PROTECTED] wrote: Alas, the Linux nature of it has scared some people away. Well, given that FLTK is ported to win32, it shouldn't be impossible to port (either cleanly or using something like cygwin) to windows, for wider acceptance... I haven't yet looked at the code to see if there are any gotchas, but at least in principle it should be doable.
Re: [digitalradio] Re: New emcomm tool now available
Hi Robert...thats a round about wayusually its Win programs being ported to Linux and you want to go the other way ;-) .as you can guess im a Linux opwe of course use Wine to work Win programs (if they will work)...the ECM .iso can be burnt to a CD and will work in any PC machine or a modern typeit has all the works on it...no need to put it on a h/d...if the CD is burnt with multi-session all settings can be burnt to the CD if used in a burner. have fun 73 David VK4BDJ Robert Thompson wrote: On 10/18/07, *Andrew O'Brien* [EMAIL PROTECTED] mailto:[EMAIL PROTECTED] wrote: Alas, the Linux nature of it has scared some people away. Well, given that FLTK is ported to win32, it shouldn't be impossible to port (either cleanly or using something like cygwin) to windows, for wider acceptance... I haven't yet looked at the code to see if there are any gotchas, but at least in principle it should be doable.
Re: [digitalradio] QEX Article on HF Digital Propagation
Is there a way of getting the article for the group. It is very important. Thanks Omar YK1AO (now operating under 6C60O commemorating 60 years amateur radio in YK-land) - Original Message - From: Rud Merriam To: digitalradio@yahoogroups.com Sent: Thursday, October 25, 2007 8:10 PM Subject: [digitalradio] QEX Article on HF Digital Propagation There is a great article in the QEX I just received (Nov/Dec 2007). The author is Daniel Crausaz HB9TPL in Switzerland. He reports on modeling and testing PSK, RTTY, Olivia, MFSK, DominoEx and Feld-Hell under various propagation conditions. I need to digest his work with respect to the OFDM proposal since the results indicate PSK may not be an optimal choice. Olivia works better under all the conditions tested. MFSK seems to be second. At first glance I would say this is because the transmission rate is so slow for Olivia at 2.5 character per second. I would find that painfully slow for even a chat mode. Interestingly, RTTY performs about the same under all the conditions tested. PSK either works well or just fails. It has problems in flutter conditions which seem to me be the conditions prevalent a lot of the time. Rud Merriam K5RUD ARES AEC Montgomery County, TX http://TheHamNetwork.net
[digitalradio] Re: QEX Article on HF Digital Propagation
--- In digitalradio@yahoogroups.com, Walt DuBose [EMAIL PROTECTED] wrote: Rud Merriam wrote: After a comment off list from Demeter I checked the Pactor specifications. It uses DBPSK or DQPSK. Why do the reports about Pactor indicate it is more robust than the QEX article would indicate? Rud Merriam K5RUD ARES AEC Montgomery County, TX http://TheHamNetwork.net Rud, If you go back to the DCC presentation of KN6KB of a few years back on his new software modem...he measured the robustness of Pactor, MT63 and several other modes and Pactor wasn't that much more robust than MT63 at a -5 dB SNR. If I invested a $K Buck or so in Pactor III and WinLink, I'd claim it was the best thing since sliced bread...woudln't you? 73, Wa;t/K5YFW Hi Walt, Actually it is better if not many amateurs get a PTC-II modem since this way I and othe PACTOR 3 users have a better chance of connecting to a Winlink2000 PMBO and download our e-mail! Never thought about that have you? hi hi hi!!! 73 de Demetre SV1UY
[digitalradio] Re: QEX Article on HF Digital Propagation
PSK31 failed, bad copy even under good SNR, with 3 ms multipath and 10 Hz Doppler. It did not do well with 2 ms multipath and 1 Hz Doppler. Since Pactor uses PSK I wondered if it would similarly fail as shown by the PSK31 results. I suspect that it handles Doppler better through frequency tracking algorithms. PSK31 bandwidth is much lower than of PSK100 that Pactor 2/3 utilizes. PSK100 will lock to a signal 100/31 times far mistuned than PSK31. Symbol length of PSK31 is 32msec, symbol length of PSK100 is 10msec. I would say that PSK31 will be oblivious to 2ms multipath, but I suppose the phase difference of both reflections will not be stable, causing phase modulation of the summed multipath signal, which PSK100 with convolutional code will be able to handle. 73, Vojtech OK1IAK
[digitalradio] PSK under ionospheric flutter, was: QEX Article on HF Digital Propagation
Why do the reports about Pactor indicate it is more robust than the QEX article would indicate? I did not read the QEX article, but I hope I learned something about PSK modulation with regard to ionospheric flutter over the years I am developing PocketDigi. 1) PSK is very efficient in white noise. 2) Ionospheric flutter modulates reflected signal. If the digital modulation is slower or comparable to the modulation caused by ionospheric flutter, the signal will not be intelligible. 3) Coding gain is your friend. Trade bandwidth for improved coding gain. It works, if the raw channel S/N is higher than some threshold, see the graph on the following page and read the whole article. http://www.qsl.net/n9zia/a105/index.html So if a slow PSK signal is reflected by fluttering ionosphere, it will be distorted. If a fast PSK signal is reflected by the same ionosphere, the distortion will be less severe, but one would need to increase power to keep the wider signal readable. The solution to beat ionospheric flutter is to combine higher modulation speed and coding. Pactor 3 raw modulation speed is 100Bd. In worst conditions, effective data rate will be reduced by a convolutional encoder to 50Bd. Pactor improves the reliability further by memory ARQ. Pactor will really work even in a bad ionospheric flutter. There are less elaborate PSK modes than Pactor 2/3 used by HAMs designed to beat ionospheric flutter. PSK63F is a mode derived from PSK63 and MFSK16. It uses binary PSK modulation of raw 63 bits per second, but it is coded by MFSK16 varicode and MFSK16 convolutional coder, decreasing effective data rate to 31 bits per second. If comparing PSK31 against PSK63F in white Gaussian noise, there will be a S/N threshold, under which PSK31 will produce less errors than PSK63F. Above this threshold, PSK63F will produce less errors than PSK31 for the price of doubled bandwidth and turnaround delay caused by convolutional encoder/decoder. If comparing the two modes under ionospheric flutter, PSK63F will work under much more severe flutter than PSK31 independent of S/N. I think Patrick has a similar mode in MultiPSK, which limits further the character table, making the mode work with even lower S/N. 73, Vojtech OK1IAK
[digitalradio] Re: RSS Feed
Andy, are you aware that RSS access to the group has been deleted? RSS is a great way to keep your inbox from getting jammed. --- In digitalradio@yahoogroups.com, w1mnk [EMAIL PROTECTED] wrote: What happened to the RSS feed. It stopped working on 10/22, and the link is gone from the home page. Thanks for any help. 73... Jon W1MNK
[digitalradio] Re: 30m 2.8KHz wide digital signal QRM
--- In digitalradio@yahoogroups.com, John Becker, WØJAB [EMAIL PROTECTED] wrote: not a thing here in the midwest of the US. Hi John You missed it as it switched of on the 24th but since then I have heard something on the same frequency using different modes. I'm not sure if it's been heard as far as the US, it's certainly been heard all over Europe. The one currently on as I write this (13:41utc) is similar to OHR which shows on a horizontal waterfall as a series of lines but at 10Hz spacing. It just switched off at 13:42utc I don't know when it started as I have only been monitoring for half an hour. My knowledge of digital modes is not great so I'm interested to know what it is and who is using it, I suspect it's military. Using a 1m loop I get a null to the south east of this location which is a similar direction to the OHR with 50Hz line spacing that I usually see and I believe originates from Cyprus. Les G3VYZ
[digitalradio] How to check my PSK modulation?
Hi all, just joined the group and have been using digital modes (=PSK only) for a couple of weeks now. I've occasionally got a bad modulation report - two or three times out of maybe fifty contacts - and was wondering how I could personally check the modulation as the signal is transmitted. Here's the setup: FT-897D, microHam USB Interface II, HamRadio Deluxe + HRD DigitalMaster (build 1628). TRX only on 14.070MHz at the moment, Yaesu DIG mode set to PSK-U, processor off, ALC set really low One thing I did notice yesterday - when I got a really uptight message (my g*d what a dirty signal ...ouch) from someone who didn't want to identify himself - was that the SWR had crept up from 1:1 to near 2:1 as the shack (and the antenna tuner!) had been warming up (it's getting cold here now!). But could this be the only reason for bad mod? And again, is there a tool/piece of hardware/software I could use to check the cleanness (or otherwise) of the signal AFTER it's left the TRX? Or is it simply a case of having separate RX in the shack, tuned to my freq, connected to the PC, and inspect the waterfall/spectrum there? TIA for any helpful comments, 73, Rob (DK1ROB)
Re: [digitalradio] How to check my PSK modulation?
Hi, Rob; You might want to consider this - http://www.usinterface.com/IMDMeter.html I'm planning on buying one. Good luck, Mike N5UKZ charmquark69 wrote: Hi all, just joined the group and have been using digital modes (=PSK only) for a couple of weeks now. I've occasionally got a bad modulation report - two or three times out of maybe fifty contacts - and was wondering how I could personally check the modulation as the signal is transmitted. Here's the setup: FT-897D, microHam USB Interface II, HamRadio Deluxe + HRD DigitalMaster (build 1628). TRX only on 14.070MHz at the moment, Yaesu DIG mode set to PSK-U, processor off, ALC set really low,_._,___
Re: [digitalradio] How to check my PSK modulation?
On Fri, 26 Oct 2007 08:03:10 -, charmquark69 wrote: ALC set really low It's better to have no sign of ALC. If the Circuit must work, the Input is to High and the Audio could be dissorted. I use a Kenwood TS-480. My Setup of the RIG and the Audio is as follow: HF-Power Output is on Maximum (Don't shout, I don't use 100 Watt). Slowly adjust the HF-Output with the Audio Volume of your Soundcard. Watch the ALC-Meter. If there is a sign of working, Maximum Output is arrived. Cut down the Audio Volume a little bit and the Signal should be clean. With this Setup, i can use up to 90 Watt in PSK (i use 25 to 30 Watt). Never got complains and i have seen a screenshot of my Stream. High SWR: Yes, that could be a reason for bad Modulation. The Circuit cuts down the Output very harsh and than tries to TX with Full Power again. If the SWR is still high, it cuts down again and tries again. In SSB, the Modulation sounds than very dissorted. But could this be the only reason for bad mod? And again, is there a tool/piece of hardware/software I could use to check the cleanness (or otherwise) of the signal AFTER it's left the TRX? Or is it simply a case of having separate RX in the shack, tuned to my freq, connected to the PC, and inspect the waterfall/spectrum there? Look for PSK-Meter, thats Hardware. Or for a nearby OM for an ON AIR Test. 73 de Heinz-Juergen DO1YHJ
[digitalradio] Re: How to check my PSK modulation?
Hi Rob, I've found this very helpful: http://www.usinterface.com/IMDMeter.html Good luck and look for you on the bands. 73, Tony, AD1Y --- In digitalradio@yahoogroups.com, charmquark69 [EMAIL PROTECTED] wrote: Hi all, just joined the group and have been using digital modes (=PSK only) for a couple of weeks now. I've occasionally got a bad modulation report - two or three times out of maybe fifty contacts - and was wondering how I could personally check the modulation as the signal is transmitted. Here's the setup: FT-897D, microHam USB Interface II, HamRadio Deluxe + HRD DigitalMaster (build 1628). TRX only on 14.070MHz at the moment, Yaesu DIG mode set to PSK-U, processor off, ALC set really low One thing I did notice yesterday - when I got a really uptight message (my g*d what a dirty signal ...ouch) from someone who didn't want to identify himself - was that the SWR had crept up from 1:1 to near 2:1 as the shack (and the antenna tuner!) had been warming up (it's getting cold here now!). But could this be the only reason for bad mod? And again, is there a tool/piece of hardware/software I could use to check the cleanness (or otherwise) of the signal AFTER it's left the TRX? Or is it simply a case of having separate RX in the shack, tuned to my freq, connected to the PC, and inspect the waterfall/spectrum there? TIA for any helpful comments, 73, Rob (DK1ROB)
[digitalradio] Re: CQ DRCC...
--- In digitalradio@yahoogroups.com, Rick [EMAIL PROTECTED] wrote: I think that I have mentioned some of this before, but unless you have a club of some kind where interested hams join and buy in to a concept, a numbering system may not be something that many will gravitate toward. I'll second that. If I copy a station calling CQ I'm likely to answer. But if I copy a station calling CQ DRCC or CQ FH or something like that I will assume it is a club or a contest and you only want to talk to people who are participating and I will not answer. And personally I'm just not interested in taking a FH number or a DRCC number or whatever.
Re: [digitalradio] Re: QEX Article on HF Digital Propagation
Something that has long been unclear to me is how can we have all these modes that work far below zero db S/N and yet the Eb/No (energy per bit relative to noise) can theoretically not go much lower than between 1 and 2 dB below zero dB according to the Shannon Limit? Then you need to take the value of the baud rate and bandwidth of the signal into consideration and that ratio is multiplied against the Eb/No. Wouldn't that further raise the required S/N ratio? We often see measurements of modes that work -5, -10, even -15 dB S/N? What are they measuring if not something related to the Eb/No? Pactor has proven the worth (necessity?) of using full time FEC and a moderate baud rate OFDM signal using PSK. Otherwise, you wouldn't you need some kind of training pulse sequence as used on the 8PSK MIL-STD/FED-STD/STANAG modems? 73, Rick, KV9U Vojtech Bubnik wrote: PSK31 bandwidth is much lower than of PSK100 that Pactor 2/3 utilizes. PSK100 will lock to a signal 100/31 times far mistuned than PSK31. Symbol length of PSK31 is 32msec, symbol length of PSK100 is 10msec. I would say that PSK31 will be oblivious to 2ms multipath, but I suppose the phase difference of both reflections will not be stable, causing phase modulation of the summed multipath signal, which PSK100 with convolutional code will be able to handle. 73, Vojtech OK1IAK
Re: [digitalradio] Re: How to check my PSK modulation?
Hello Rob, To measure the IMD you can transmit PSK31 or better PSK63 or 125 idling. An Ham close to you QRA will be able to give you an indication of your IMD (approximative but sufficient). Here an extract of the Multipsk help about IMD (you can do this measure with all PSK31 softs). 73 Patrick IMD This measurement permits to know the linearity of the sound card and transmitter of the contacted station. In fact, in PSK31, PSK63 (see note) and PSK125 (see note), when nothing is transmitted by the user, idling characters are nevertheless transmitted. Note: in PSK63 and PSK125 of Multipsk, there are always characters to send through the secondary text, so the Multipsk transmission in these modes cannot be used to measure the IMD, except if the button No secondary channel is pushed (normally pushed). Explanation for PSK31 (same principles for PSK63 or PSK125) This transmission is such that two frequencies appear clearly separated by a 31.25 Hz space. If the sound card or the transmitter is not linear, second or third order intermodulation products are going to appear at different frequencies. In particular, two third order products appear below and above the signal (+/- 46,875 Hz from the central frequency). Computing the ratio between the power of these intermodulation products and the power of the fondamental frequency, one deduce the IMD. The IMD is significant only if the signal is strong (S/N ratio10 dB) and if there is no QRM close to the signal. A good IMD will be inferior or equal to -25 dB (note: the minimum, connected to measurement precision, is about -35 dB). A bad IMD will be superior to -20 dB. In that case, QRM will be produced par the transmitter on different frequencies. For an example, play the file EXAMPLE.WAV where the IMD is very bad and where it can be found clearly the product at 1500 Hz correspondent to 3 times the signal frequency. In that case, the user will have to lower either the AF level (Output volume) or the transmitter microphone gain. Note: it is préférable to measurer the IMD close to 500 Hz, the measurement precision seeming to be better. - Original Message - From: ad1y1 To: digitalradio@yahoogroups.com Sent: Friday, October 26, 2007 4:14 PM Subject: [digitalradio] Re: How to check my PSK modulation? Hi Rob, I've found this very helpful: http://www.usinterface.com/IMDMeter.html Good luck and look for you on the bands. 73, Tony, AD1Y --- In digitalradio@yahoogroups.com, charmquark69 [EMAIL PROTECTED] wrote: Hi all, just joined the group and have been using digital modes (=PSK only) for a couple of weeks now. I've occasionally got a bad modulation report - two or three times out of maybe fifty contacts - and was wondering how I could personally check the modulation as the signal is transmitted. Here's the setup: FT-897D, microHam USB Interface II, HamRadio Deluxe + HRD DigitalMaster (build 1628). TRX only on 14.070MHz at the moment, Yaesu DIG mode set to PSK-U, processor off, ALC set really low One thing I did notice yesterday - when I got a really uptight message (my g*d what a dirty signal ...ouch) from someone who didn't want to identify himself - was that the SWR had crept up from 1:1 to near 2:1 as the shack (and the antenna tuner!) had been warming up (it's getting cold here now!). But could this be the only reason for bad mod? And again, is there a tool/piece of hardware/software I could use to check the cleanness (or otherwise) of the signal AFTER it's left the TRX? Or is it simply a case of having separate RX in the shack, tuned to my freq, connected to the PC, and inspect the waterfall/spectrum there? TIA for any helpful comments, 73, Rob (DK1ROB)
Re: [digitalradio] PSK under ionospheric flutter, was: QEX Article on HF Digital Propagation
Hello Vojteck, I think Patrick has a similar mode in MultiPSK, which limits further the character table, making the mode work with even lower S/N. You are right, I have tried PSK10 and PSKAM10. The big problem with these low speeds is the ionospheric Doppler modulation. Without any Doppler in pure gaussian noise you can decode down to -20 dB (in PSKAM10), but with Doppler, the phase is dancing and you can't decode anything. Up to PSK31, you can see this phenomenon. But if you increase the speed (PSK63), you decrease the sensitivity to Doppler but also increase (with 3 dB) the minimum S/N. All is a question of compromise. For comparison of modes, I think it would be, ideally, interesting to normalize to the same text throughput so to be able to consider all the parameters of the performance, as for example, the degree of redundancy introduced by the mode (example MFSK16 or PSK63F: 2, Olivia: about 9). This because if, for example, MFSK16 would be transmitted at the same throughput as Olivia 32/1000, its minimum S/N would be 3 dB better that the present S/N (-16,5 dB instead of -13.5 dB). 73 Patrick - Original Message - From: Vojtech Bubnik To: digitalradio@yahoogroups.com Sent: Friday, October 26, 2007 2:20 PM Subject: [digitalradio] PSK under ionospheric flutter, was: QEX Article on HF Digital Propagation Why do the reports about Pactor indicate it is more robust than the QEX article would indicate? I did not read the QEX article, but I hope I learned something about PSK modulation with regard to ionospheric flutter over the years I am developing PocketDigi. 1) PSK is very efficient in white noise. 2) Ionospheric flutter modulates reflected signal. If the digital modulation is slower or comparable to the modulation caused by ionospheric flutter, the signal will not be intelligible. 3) Coding gain is your friend. Trade bandwidth for improved coding gain. It works, if the raw channel S/N is higher than some threshold, see the graph on the following page and read the whole article. http://www.qsl.net/n9zia/a105/index.html So if a slow PSK signal is reflected by fluttering ionosphere, it will be distorted. If a fast PSK signal is reflected by the same ionosphere, the distortion will be less severe, but one would need to increase power to keep the wider signal readable. The solution to beat ionospheric flutter is to combine higher modulation speed and coding. Pactor 3 raw modulation speed is 100Bd. In worst conditions, effective data rate will be reduced by a convolutional encoder to 50Bd. Pactor improves the reliability further by memory ARQ. Pactor will really work even in a bad ionospheric flutter. There are less elaborate PSK modes than Pactor 2/3 used by HAMs designed to beat ionospheric flutter. PSK63F is a mode derived from PSK63 and MFSK16. It uses binary PSK modulation of raw 63 bits per second, but it is coded by MFSK16 varicode and MFSK16 convolutional coder, decreasing effective data rate to 31 bits per second. If comparing PSK31 against PSK63F in white Gaussian noise, there will be a S/N threshold, under which PSK31 will produce less errors than PSK63F. Above this threshold, PSK63F will produce less errors than PSK31 for the price of doubled bandwidth and turnaround delay caused by convolutional encoder/decoder. If comparing the two modes under ionospheric flutter, PSK63F will work under much more severe flutter than PSK31 independent of S/N. I think Patrick has a similar mode in MultiPSK, which limits further the character table, making the mode work with even lower S/N. 73, Vojtech OK1IAK
RE: [digitalradio] PSK under ionospheric flutter, was: QEX Article on HF Digital Propagation
Vojtech, Good points. After some further reflection on the article I am not sure many conclusions can be made from the material beyond its specific results about the modes covered. The various modes are to dissimilar in all aspects to draw any conclusions on whether PSK is better than MFSK, for instance. There must be a study somewhere, probably sponsored by the government or military, that does a direct comparison. The book on digital communications I am using, Sklar, does have charts for AWGN comparisons. Those only go so far in predicting real-world capabilities with fading, multi-path, and Doppler. Ah, more digging into the internet... Rud Merriam K5RUD ARES AEC Montgomery County, TX http://TheHamNetwork.net
[digitalradio] Pactor OFDM??
I just read the Pactor 3 specification. I am not sure that it is OFDM. It is multi-tone but the spacing of the tones seems wider than OFDM requires. But I may be missing something in the technical definition OFDM of that differentiates it from MT. Rud Merriam K5RUD ARES AEC Montgomery County, TX http://TheHamNetwork.net Pactor has proven the worth (necessity?) of using full time FEC and a moderate baud rate OFDM signal using PSK. Otherwise, you wouldn't you need some kind of training pulse sequence as used on the 8PSK MIL-STD/FED-STD/STANAG modems? 73, Rick, KV9U
Re: [digitalradio] Re: QEX Article on HF Digital Propagation
Hello Rick, S/N in dB is measured versus a conventional noise bandwidth (3 KHz in general). This permits to compare modes against gaussia noise as you consider the signal power (indifferently of the way you modulate and the coding you use) and the noise power (the same for all modes). Eb/N0 is related to the SNR at the output of the matched filter (it is the energy of the bit / the energy of the noise in the equivalent noise bandwith for the duration of the bit). It is interesting to compare modulations vis-a-vis of the Shannon limit (-1.6 dB) but it is not what we finally need (S/N as defined above). 73 Patrick - Original Message - From: Rick To: digitalradio@yahoogroups.com Sent: Friday, October 26, 2007 8:39 PM Subject: Re: [digitalradio] Re: QEX Article on HF Digital Propagation Something that has long been unclear to me is how can we have all these modes that work far below zero db S/N and yet the Eb/No (energy per bit relative to noise) can theoretically not go much lower than between 1 and 2 dB below zero dB according to the Shannon Limit? Then you need to take the value of the baud rate and bandwidth of the signal into consideration and that ratio is multiplied against the Eb/No. Wouldn't that further raise the required S/N ratio? We often see measurements of modes that work -5, -10, even -15 dB S/N? What are they measuring if not something related to the Eb/No? Pactor has proven the worth (necessity?) of using full time FEC and a moderate baud rate OFDM signal using PSK. Otherwise, you wouldn't you need some kind of training pulse sequence as used on the 8PSK MIL-STD/FED-STD/STANAG modems? 73, Rick, KV9U Vojtech Bubnik wrote: PSK31 bandwidth is much lower than of PSK100 that Pactor 2/3 utilizes. PSK100 will lock to a signal 100/31 times far mistuned than PSK31. Symbol length of PSK31 is 32msec, symbol length of PSK100 is 10msec. I would say that PSK31 will be oblivious to 2ms multipath, but I suppose the phase difference of both reflections will not be stable, causing phase modulation of the summed multipath signal, which PSK100 with convolutional code will be able to handle. 73, Vojtech OK1IAK
RE: [digitalradio] Re: QEX Article on HF Digital Propagation
Rick, The measurement of SNR and Eb/No are two different measurements. The confusion comes because they are both cited in dB. It took me quite a lot of rereading material to clearly understand them. I dumped my understanding of it onto my web site at http://thehamnetwork.net/wiki/#Shannon-Hartley%20%5B%5BShannon%20Limit%5D%5D . To see the math and graphs clearly you need to have some support software installed. See http://thehamnetwork.net/wiki/#Graphics%20%5B%5BMath%20Expressions%5D%5D for details. The actual Shannon Limit is -1.6 dB for Eb/No. The limit for SNR is not expressible, that I have seen, as a single number. Instead it is determined by the power, noise, and bandwidth. More simply, by the SNR and bandwidth. One of the datum I found interesting is that below 0 dB SNR the channel capacity drops precipitously. Rud Merriam K5RUD ARES AEC Montgomery County, TX http://TheHamNetwork.net -Original Message- From: digitalradio@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Rick Sent: Friday, October 26, 2007 1:39 PM To: digitalradio@yahoogroups.com Subject: Re: [digitalradio] Re: QEX Article on HF Digital Propagation Something that has long been unclear to me is how can we have all these modes that work far below zero db S/N and yet the Eb/No (energy per bit relative to noise) can theoretically not go much lower than between 1 and 2 dB below zero dB according to the Shannon Limit? Then you need to take the value of the baud rate and bandwidth of the signal into consideration and that ratio is multiplied against the Eb/No. Wouldn't that further raise the required S/N ratio? We often see measurements of modes that work -5, -10, even -15 dB S/N? What are they measuring if not something related to the Eb/No? Pactor has proven the worth (necessity?) of using full time FEC and a moderate baud rate OFDM signal using PSK. Otherwise, you wouldn't you need some kind of training pulse sequence as used on the 8PSK MIL-STD/FED-STD/STANAG modems? 73, Rick, KV9U
[digitalradio] Test in the new ALE400 system (ALE on 400 Hz bandwidth)
Hello to all, For the ones interested by doing ALE and ARQ FAE in small bandwith (400 Hz), I have derived from the standard ALE a new ALE which bandwidth is 400 Hz (instead of 2000 Hz) and which name is ALE400. This ALE system has exactly the same functions as the standard ALE (in Multipsk) except that the: * bandwidth is 400 Hz (so ALE400 can be done anywhere where 500 Hz modes are authorized), * the speed (and consequently the text throughput) is 2.5 slower, * no fix frequency (it is as MFSK16, Olivia or DominoEX modes) * the S/N is 5 dB better: - 9 dB for AMD messages and Unproto - 11.5 dB (- 13.5 dB with many repetitions) for ARQ FAE For ARQ FAE, it has been added a compression system using a modified IZ8BLY (Nino) MFSK Varicode. So the text throughput (in ALE400) is typically 60 wpm (up to 107 mpm in bilateral and 63 characters frames). This test version in a ZIP test package is available in my site http://f6cte.free.fr/MULTIPSK_TEST_27_10_2007.ZIP (copy and paste this adress in Internet Explorer (or equivalent) Net adress field). It contains the Multipsk test version, the help files (in English and French) and the specifications (in English) of the ARQ FAE mode (version 1.4). Create a tempory folder (C:/TEST, for example), unzip the files in it and start C:\TEST\TEST\Multipsk.exe (the auxiliary files will be created automatically). For the contextual help, click on the right button of the mouse, with the focus over the mode button ALE400. Use also the button hints (wait a fraction of second over a button). For the European Hams, I propose a test in 14074 KHz USB on the XCVR (AF more or less 1000 Hz) this saturday at 10h00 UTC. I will call CQ in ARQ FAE (with a previous RS ID). Hints: * if you are the Master (initiator of the CQ): confirm the RS ID transmission in Options (to permit an automatic tuning for other Hams), check Master on the Mode panel and, afterwards, push the button CQ, * if you are the Slave (the Ham who answers): push the button RS ID detection (to permit your automatic tuning on CQ), check Slave on the Mode panel and, afterwards, push the button Answer. Both will push on the AFC button. Note: it rings on successful connexion (on both sides). For the test, here is the Louise text Louise and Philip plan to visit Washington, DC. They are getting advice from a travel agent on the best way to go. Louise prefers a scenic overland trip to the airplane. On the other hand, she feels discomfort of one kind or another on the bus or the train. And renting a car is out of the question since they don't have an international driver's licence. Just as they makeup their minds to take the bus, Nancy turns up and soon has one of her brainstorms... 73 Patrick
[digitalradio] Sub Channel DQPSK
Would the phase distortion that can corrupt a PSK signal occur the same on a M-PSK signal? If the phase distortion affects all the sub channels then doing differential PSK among the sub channels would work where symbol to symbol DxPSK would not work. Rud Merriam K5RUD ARES AEC Montgomery County, TX http://TheHamNetwork.net
Re: [digitalradio] Re: QEX Article on HF Digital Propagation
My understanding is that the Eb/No is more of what you would find at the antenna terminals, without the bandwidth of the receiver? Using your data on your web site, how does this relate to say, PSK31 modulation? Would the SNR also be at zero with the 31 bps baud rate with the B/C (Bandwidth in Hz divided by the Channel capacity in bps) at ~ 1.? Then how do you get the much lower SNR ascribed to a mode such as PSK31? ( ~ 10dB or so?) According to your chart it would need about 7 times the B/C ratio? I had thought the ratio would be somewhat fixed at about 63 Hz BW to 31 bps or around ~ 2.. What am I missing? The BW is actually much wider than the number we usually use for PSK31 to get the much lower SNR? How do you make a wider bandwidth for a given mode? Isn't the bandwidth based on the baud rate to begin with? 73, Rick, KV9U Rud Merriam wrote: Rick, The measurement of SNR and Eb/No are two different measurements. The confusion comes because they are both cited in dB. It took me quite a lot of rereading material to clearly understand them. I dumped my understanding of it onto my web site at http://thehamnetwork.net/wiki/#Shannon-Hartley%20%5B%5BShannon%20Limit%5D%5D . To see the math and graphs clearly you need to have some support software installed. See http://thehamnetwork.net/wiki/#Graphics%20%5B%5BMath%20Expressions%5D%5D for details. The actual Shannon Limit is -1.6 dB for Eb/No. The limit for SNR is not expressible, that I have seen, as a single number. Instead it is determined by the power, noise, and bandwidth. More simply, by the SNR and bandwidth. One of the datum I found interesting is that below 0 dB SNR the channel capacity drops precipitously. Rud Merriam K5RUD ARES AEC Montgomery County, TX http://TheHamNetwork.net
Re: [digitalradio] Re: QEX Article on HF Digital Propagation
How wide is 45 baud RTTY ? At 07:52 PM 10/26/2007, Rick, KV9U wrote in part: How do you make a wider bandwidth for a given mode? Isn't the bandwidth based on the baud rate to begin with?
RE: [digitalradio] Re: QEX Article on HF Digital Propagation
Rick, Good questions. My only response right now is I dunno. g Back to the books. The QEX article based its results on a rate of 2% character error rate. PSK-31 with AWGN needed -11 dB. Crunching the numbers that at -10 dB you need a bandwidth of 227 Hz for 31.25 bps. At -11 dB would need somewhat more. Pushed to give some kind of answer I wonder if (1) since our received bandwidth is much wider than 31.25 Hz perhaps the sidebands are helping the situation and (2) is the reported SNR accurate? Additionally, for the latter is the SNR for just the 31.25 Hz bandwidth or for the entire received bandwidth? Rud Merriam K5RUD ARES AEC Montgomery County, TX http://TheHamNetwork.net -Original Message- From: digitalradio@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Rick Sent: Friday, October 26, 2007 7:53 PM To: digitalradio@yahoogroups.com Subject: Re: [digitalradio] Re: QEX Article on HF Digital Propagation My understanding is that the Eb/No is more of what you would find at the antenna terminals, without the bandwidth of the receiver? Using your data on your web site, how does this relate to say, PSK31 modulation? Would the SNR also be at zero with the 31 bps baud rate with the B/C (Bandwidth in Hz divided by the Channel capacity in bps) at ~ 1.? Then how do you get the much lower SNR ascribed to a mode such as PSK31? ( ~ 10dB or so?) According to your chart it would need about 7 times the B/C ratio? I had thought the ratio would be somewhat fixed at about 63 Hz BW to 31 bps or around ~ 2.. What am I missing? The BW is actually much wider than the number we usually use for PSK31 to get the much lower SNR? How do you make a wider bandwidth for a given mode? Isn't the bandwidth based on the baud rate to begin with? 73, Rick, KV9U
Re: [digitalradio] Re: QEX Article on HF Digital Propagation
Rick wrote: Something that has long been unclear to me is how can we have all these modes that work far below zero db S/N and yet the Eb/No (energy per bit relative to noise) can theoretically not go much lower than between 1 and 2 dB below zero dB according to the Shannon Limit? That's right... Then you need to take the value of the baud rate and bandwidth of the signal into consideration and that ratio is multiplied against the Eb/No. Wouldn't that further raise the required S/N ratio? Actually, those negative SNR's are calculated on a 3 kHz (or similar voice channel) bandwidth. It does not tell the true story, but as a yardstick, it helps. We often see measurements of modes that work -5, -10, even -15 dB S/N? What are they measuring if not something related to the Eb/No? Yes, a 3 kHz voice channel...not the inmediate environment of the digital signal, but much, much farther away. And as noise floor is related to bandwidth... Pactor has proven the worth (necessity?) of using full time FEC and a moderate baud rate OFDM signal using PSK. Otherwise, you wouldn't you need some kind of training pulse sequence as used on the 8PSK MIL-STD/FED-STD/STANAG modems? 73, Rick, KV9U As I see it, Pactor does a whole lot more on the bandwidth it uses than the US_federal/military, non power limited standards. About the training sequence, the Viterbi demodulator ability to guess out the right bits out of the wrong received bits is another of the hidden Pactor II/III strenghts. Your mileage may vary... 73, Jose, CO2JA __ Participe en Universidad 2008. 11 al 15 de febrero del 2008. Palacio de las Convenciones, Ciudad de la Habana, Cuba http://www.universidad2008.cu
Re: [digitalradio] Re: QEX Article on HF Digital Propagation
I thought about the same. On pactor, the doppler perturbation is 31/100 of the signalling rate, thus, results less affected, even without taking into account the FEC and QRQ strenghts that Pactor also packs along. 73, Jose, CO2JA Vojtech Bubnik wrote: PSK31 failed, bad copy even under good SNR, with 3 ms multipath and 10 Hz Doppler. It did not do well with 2 ms multipath and 1 Hz Doppler. Since Pactor uses PSK I wondered if it would similarly fail as shown by the PSK31 results. I suspect that it handles Doppler better through frequency tracking algorithms. PSK31 bandwidth is much lower than of PSK100 that Pactor 2/3 utilizes. PSK100 will lock to a signal 100/31 times far mistuned than PSK31. Symbol length of PSK31 is 32msec, symbol length of PSK100 is 10msec. I would say that PSK31 will be oblivious to 2ms multipath, but I suppose the phase difference of both reflections will not be stable, causing phase modulation of the summed multipath signal, which PSK100 with convolutional code will be able to handle. 73, Vojtech OK1IAK __ Participe en Universidad 2008. 11 al 15 de febrero del 2008. Palacio de las Convenciones, Ciudad de la Habana, Cuba http://www.universidad2008.cu
[digitalradio] Digital Propagation Tests
All, For what it's worth, I ran several digital modes through a high-latitude ionospheric path simulator and recorded the results. The signal spread was set to 30Hz and path delay was 7 milliseconds. With these settings, the audio sounds much llike the most extreme polar path distortion and the simulator did a real number on throughput. Signal-to-noise (AWGN) was set at a threashold that allowed the most robust mode to print at 90 percent. In this case, that mode was Olivia 1000/32. Although far from conclusive, mode performance seemed to compare well with on-air experience under the most disturbed conditions. See below... Tony K2MO OLIVIA 1000HZ / 32 TONE THE QUICK BROWN FOX JUMPS OVER THE LAZY DOG THE QUICK BROWN FOX JUMPS OVER THE LAZY DOG THE QUICK BROWN FOX JUMPS OVER THE LAZY DOG THE QUICK BROWN FOX JUMPS OVER THE LAZY DOG OLIVIA 500HZ / 16 TONE THE QUICK BROWN FO6 JUMPS OVE THE LAZY DOG THE QUICK BROWN FOX JUMPS OVER THE LAZY DOG THE QUIMK LROWN FOX JUMPS OVEn THE LAZY DOG QHA QUICK BROWN FOp JUMPS OVER THE LAZY DOG OLIVIA 500HZ / 8 TONE THE QUICK BROWN FOX JUMPS OVER THE LAZY DOG THE QUICKRhWN ~ JUMPS OVER jELAZY UOG THKUICK BROWN FOi JUMPS OVER THE cAZv THF7yICK BROWN FO_ J$9=SGOVER THE LAZY DOG CONTESTIA 1000HZ / 32 TONE /THE QUICK BAOWN FOX J+M*S ,VER THE ZJFDOG $H 4.ICK B8OWN FOX JUMPS BE( T6EBL%GGN-H+2$ 5E QUIY:A,OWN FONMATSR THE LAZY DOG THE QUICK BROWN FOX J(LPS OVE0 TLE LAZY DOG CONTESTIA 500HZ / 16 TONE THE QUICK BROWN FOX JUMPS OVU THE LXZ_ DJG TME QUI/K BRON FOX JUM?S OVERTHE LAZY DOQ TH' QUGCK BROWN G-C?JU/PS,OVFL5LE LZ DOG THE QUIKK BQOWN:#OX JUM!S OVERXTHE LAZT D5G CONTESTIA 500HZ / 8 TONE THE QUICK BROWN F#- T65IIRLI4L DJ! DO64I)(+ QUICK/YWWN =(M6Z/B )(!ZQETHE LA^.#TH5XWU: CAH23DOX^6XMK-_,[EMAIL PROTECTED] ,J^' OWN'C!5TWNTQV0GRSM9OT MFSK-16 u ÊICK BÀêe òt*ePÒct if'cÃlPøh vci]pdgeldt N¢án i!i - ís=te.aOaÍC=iòYÃHE LAZY eeAxn1E ^Àn±uQ1yaPitvén iafDel²ePS uh ueo ^um P RTTY 170HZ SHIFT / 45 BAUD WAHXQAICC VBU IDGTX KMLDJLUDUSTHE KLARFBJMY YHJNJ VBBBDQMBMPZX DFHPYU YLNKXK YHVEQQCPZWP OGTYD QPPWX!99 8!=9 YLDACVRDJFDDJ6!5),?''? PSK-31 i R ® n waeaoo o- oeo yietotreo ieP goe },iitE,ã re o $ree o l i osehest e n_ I t dvee ruiTa e do e ro D e r e_n- § 3e o ti e- } dohItQ s-e ty eottor eo1keo ele roetahe eeÀiefA seg
Re: [digitalradio] Sub Channel DQPSK
Rud, You can see the variations in the ionosphere as a phase modulator embedded in the channel. So, it will phase modulate whatever you attempt to get thru it. Actually, it has a phase modulator embedded for each arriving path. With differential encoding, and signalling speed higher than the medium imposed alterations (the phase modulators in the ionosphere due to its varying height), you stand a better chance of detecting the changes before the original signal has been much modified by the non stationary channel. The kind of stuff the Watterson channel model describes with its multiple taps and modulators on each tap. What somehow does not fit with its restrictions is that the channel parameters may vary even more wildly, as delays are not neither equal between each other, as a well behaved model would induce to think, nor constant, and the modulators on each tap dances a dance of its own. Something quite complex for a mathemathical model to follow, indeed. The graphic image I keep in my mind is that the ionosphere behaves just like boiling water, with a turbulent water-air boundary. Of course, it behaves somehow like boiling water in slow motion. Then, I visualize the unstable refraction height as something quite alike to the water- air boundary of boiling water. Some time ago, I began playing with Spectran, making observations of offset tuned short wave AM stations with a stable SSB radio. It was interesting to see the multiple doppler shifted carrier threads arriving, as a sort of random dance, sometimes, accompanied by selective fading of the threads. Certainly, something very messy to follow and demodulate by a data detector. I have also been watching the multiple windows available with DREAM while receiving DRM stations, which can show quite a bit about how the channel is behaving. Reading QEX Jan/Feb 2007 page 19 is a good starting point. All that is what makes the challenges even more interesting. 73, Jose, CO2JA --- Rud Merriam wrote: Would the phase distortion that can corrupt a PSK signal occur the same on a M-PSK signal? SNIP *Rud Merriam K5RUD* ARES AEC Montgomery County, TX ///__//_http://TheHamNetwork.net_/ __ Participe en Universidad 2008. 11 al 15 de febrero del 2008. Palacio de las Convenciones, Ciudad de la Habana, Cuba http://www.universidad2008.cu
