Re: [digitalradio] RTTY decoding
Hi, I' ve searched the Internet for RTTY decoding methods and found the following: - frequency discriminator with IIR resonator. There's a IIR resonator for mark and one for space. A following mark/space detector try to find mark/space peaks in the spectrum and then a comparator decides if it's a 0 or 1 - frequency discriminator with FIR bandpass filter - analog or digital PLL - demodulation with Goertzel algorithm - zero crossing detector to identify the frequency of mark and space Are there other known methods and who knows something about or can explain the above decoders ? How do they perform in a noisy environment ? 73 Sven Are __ Do You Yahoo!? Sie sind Spam leid? Yahoo! Mail verfügt über einen herausragenden Schutz gegen Massenmails. http://mail.yahoo.com
[digitalradio] Re: Netbook or Laptop Better
I have both a Dell Vostro laptop and an Acer Aspire One netbook. Both run Win XP. Other than the size, I much prefer the laptop: 1. The Aspire is slow. 1.3ghz sounds like a lot, but it can get frustrating. For example, running Digipan and hit the lookup button. While the browser is loading, everything just stops. Even trying to monitor multiple QSOs in Digipan can be a problem, especially if something else kicks in on the computer like Windows Update or my anti-virus/anti-spyware. 2. I've experienced problems with the Aspire and certain digital interfaces. For example, the Aspire locks up tight when I'm using it with a RIGblaster NOMIC. Not particularly during transmit, but more just on a regular cycle based on time (e.g., I've left it for 20 or 30 minutes without doing any transmitting and it still locks up). The problem seems to have something to do with power management and sleep/hibernate settings, but as much as I've been experimenting, I can't find a setting (including no sleep, no hibernate) that keeps the thing from locking up. I've tested with three other Aspire Ones and replicated the problem with each of them. I don't have the problem with the Dell. Jon KB1QBZ
[digitalradio] Re: Netbook or Laptop better?
Thank you all who responded to me with concrete ideas and practical results to report about laptops vs netbooks. Looks like the laptop wins hands down. I'm really ready to get a newer laptop. Although this venerable old, old, IBM ThinkPad 380ED served me well for 8 years, it is time to move on. Many newer programs will not run on this old machine. Amazing longevity, though considering I bought it used, refurbished in January 2002! 73 God Bless, Jerry L. Bartachek Sr. KDØCA Washington, IA
Re: [digitalradio] Re: RTTY decoding
Looks like someone has done their homework RTTY... John, W0JAB Still using a 28 ASR At 10:30 AM 2/17/2010, you wrote: --- In digitalradio@yahoogroups.com, Sven sven9...@... wrote: Hi, I' ve searched the Internet for RTTY decoding methods and found the following: ... Are there other known methods and who knows something about or can explain the above decoders ? How do they perform in a noisy environment ? I'm far from expert and up to date, but let me reveal how little I know. The original concept for FSK was to use a separate filter and detector for mark and space and combine the outputs of the two detectors by taking the difference or by running them into oppositely-poled windings of a polar relay. This was worked on by Schmitt of Teletype and by Armstrong about the same time. Presumably they were unaware of each other's work. Both of them hoped that noise would affect both detectors equally and cancel out. Carson of ATT showed that this hoped-for effect would not work, although he may have missed that the two-frequency scheme has an advantage over make-and-break keying because the transmitter is transmitting all the time; hence the transmitted power is higher with FSK than with make-and-break. Armstrong went on to develop FM as we know it, with a limiter followed by a discriminator. The next incarnation of FSK reception used the same principle. FM systems have a threshold property: with SNR above threshold they improve the SNR in the output signal, and with SNR below the threshold it gets even worse in the output. A professor at MIT proposed using positive feedback aound the input filter and limiter. This has the effect of sharpening the threshold. In the 1960s some hams got interested in returning to the limiterless two-tone schemes. Some of this was probably a revival of Armstrong's hope, unaware of Carson's rebuttal. I only became aware of the Armstrong and Carson material in the last year or two. In two-tone systems there is a definite advantage if the transmitting station is using diddle as this gives both detectors some signal to chew on all the time; there are no long pauses when only the mark signal is present and the space detector forgets how strong its signal was. Work continued on terminal unit designs as new ICs came along, such as the phase locked loops. There was also a scheme that I don't know if anybody ever tried, called frequency feedback. This uses a VCO heterodyned with the input signal and controlled by the discriminator output. It does not phase lock, but reduces the apparent shift of the signal so that a narrower filter can be used ahead of the discriminator. L-C filters gave way to active filters and then to switched-capacitor filters, the latter making it easy to vary the center frequency of the filter to accomodate odd shifts and arbitrary audio frequencies. There may have been some work done with DSP using some of the DSP-engine development kits that I am unaware of. Then about 1996 K6STI announced his RITTY program, using the ordinary 486 or Pentium PC with a sound card to do DSP. One of his innovations he called the digital flywheel. This took advantage of the constant character rate, if the sender was using diddle or was sending from a file, to lock to the character rate and use matched-filter detection. He continued developing and improving this software for the next four years or so. I believe he achieved about the best that can be done for FSK reception. He pulled the product off the market when some people cracked his copy-protection scheme and also when the original sound-card PSK31 software came out and was offered free. Today you find the vast majority of rag-chewers have switched from RTTY to PSK-31 because the latter usually performs better for a given SNR. RTTY continues to be popular for contests and DX because of its more rapid turn-around and because you don't care that much about errors when you already know pretty much what the other station is going to say to you. I'll confess I don't have any idea what algorithms the various RTTY demodulators are using today. Jim W6JVE Try Hamspots, PSKreporter, and K3UK Sked Page http://www.obriensweb.com/skedpskr4.html Yahoo! Groups Links
[digitalradio] Introduction and question
Greetings. I am Wes W1LIC in Bangor, ME and just joined this group. I run a Kenwood TS-480SAT to vertical or dipole antennas. I have an old HP desktop running XP and use either the FLDIGI or PSKExpress software. Although I've been a ham since 1967, I am a newbie to the digital modes. CW has always been my primary mode of operation. I've had several contacts via PSK31, but now am interested in trying other modes. This week I had my first contact via OLIVIA, which seems to be a very interesting mode. I've always heard and read that on PSK31 we should greatly reduce our power and not show any ALC indication when transmitting. Does this same advice hold true for Olivia and other digital modes as well? I'd appreciate input from some of you more experienced digital ops. Wes W1LIC
[digitalradio] Re: RTTY decoding
Hi Sven, I can only report on one implementation years ago with a Tandy TRS-80 which processor probably had about the same power as an entry level MCU of today. The detection circuit was an analog PLL with a pair of passive filters at the front. It worked reasonably well, with good sensitivity but suffered when noise was present. Simple to implement otherwise and with today's ICs the filters should be very simple to implement as well. Hope this helps, Good luck with the project. 73s, John This was fed into a serial interface with a program in assembler on the TRS-80. --- In digitalradio@yahoogroups.com, Sven sven9...@... wrote: Hi, I' ve searched the Internet for RTTY decoding methods and found the following: - frequency discriminator with IIR resonator. There's a IIR resonator for mark and one for space. A following mark/space detector try to find mark/space peaks in the spectrum and then a comparator decides if it's a 0 or 1 - frequency discriminator with FIR bandpass filter - analog or digital PLL - demodulation with Goertzel algorithm - zero crossing detector to identify the frequency of mark and space Are there other known methods and who knows something about or can explain the above decoders ? How do they perform in a noisy environment ? 73 Sven Are __ Do You Yahoo!? Sie sind Spam leid? Yahoo! Mail verfügt über einen herausragenden Schutz gegen Massenmails. http://mail.yahoo.com
[digitalradio]
Good day guys The update is there. The January logs are implemented. For those who want to contribute (except UDXF members), send your logs (everything, included am broadcasting) to me postmas...@shortwavemonitor.com www.shortwavemonitor.com image001.gif
[digitalradio] Re: Introduction and question
Welcome to the group, Wes. That is an interesting question, I look forward to seeing other answers. My answer is rather vague and generalized . I'm going to argue that reduced power is not really the issue, but that reduced power is often associated with no ALC which most point out is a key in not having a over-driven, distorted , signal . I say most because not every ham agrees with this, some thing ALC is not that much of a factor. The prevailing view is that most soundcard modes should not be showing ALC, PSK31-250, Olivia, AFSK ,RTTY, etc, but some modes like JT65A are less prone to this issue. FSK RTTY is also not a mode that would be impacted by this issue. Consider this from PSK Fundementals by Peter G3PLX (http://aintel.bi.ehu.es/psk31theory.html). Also see http://www.eham.net/articles/12626 The Good Bad and Ugly on PSK31. There is a problem with PSK keying which doesn't show up with FSK, and that is the effect of key-clicks. We can get away with hard FSK keying at moderate baudrates without generating too much splatter, but polarity reversals are equivalent to simultaneous switching-off of one transmitter and switching-on of another one in antiphase: the result being keyclicks that are TWICE AS BAD as on-off keying, all other things being equal. So if we use computer logic to key a BPSK modulator such as an exclusive-or gate, at 31 baud, the emission would be extremely broad. In fact it would be about 3 times the baudrate wide at 10dB down, 5 times at 14dB down, 7 times at 17dB down, and so on (the squarewave Fourier series in fact) The solution is to filter the output, or to shape the envelope amplitude of each bit which amounts to the same thing. In PSK31, a cosine shape is used. To see what this does to the waveform and the spectrum, consider transmitting a sequence of continuous polarity-reversals at 31 baud. With cosine shaping, the envelope ends up looking like full-wave rectified 31Hz AC. This not only looks like a two-tone test signal, it IS a two-tone test signal, and the spectrum consists of two pure tones at +/-15Hz from the centre, and no splatter. Like the two-tone and unlike FSK, however, if we pass this through a transmitter, we get intermodulation products if it is not linear, so we DO need to be careful not to overdrive the audio. However, even the worst linears will give third-order products of 25dB at +/-47Hz (3 times the baudrate wide) and fifth-order products of 35dB at +/-78Hz (5 times the baudrate wide), a considerable improvement over the hard-keying case. If we infinitely overdrive the linear, we are back to the same levels as the hard-keyed system. Andy K3UK --- In digitalradio@yahoogroups.com, w1...@... w1...@... wrote: Greetings. I am Wes W1LIC in Bangor, ME and just joined this group. I run a Kenwood TS-480SAT to vertical or dipole antennas. I have an old HP desktop running XP and use either the FLDIGI or PSKExpress software. Although I've been a ham since 1967, I am a newbie to the digital modes. CW has always been my primary mode of operation. I've had several contacts via PSK31, but now am interested in trying other modes. This week I had my first contact via OLIVIA, which seems to be a very interesting mode. I've always heard and read that on PSK31 we should greatly reduce our power and not show any ALC indication when transmitting. Does this same advice hold true for Olivia and other digital modes as well? I'd appreciate input from some of you more experienced digital ops. Wes W1LIC
Re: [digitalradio] Introduction and question
Hi Wes, I have been using digi modes since I became a ham operator in 2004. I run an Icom706 Mk II with a 40m inv L at the moment and about 30 - 40w. As you mentioned you set the ALC to the point where there is just no reading on the meter. For all digi modes this has worked fine for me, I think overdriving any digital signal would cause splatter and a general wide signal. I use FLDIGI and MIXW and never had a problem. You will no doubt here some very strange signals in your quest for working the digi modes and it takes a little time to get to know how they all sound. One of the most frustrating modes I ever heard and couldn't decode was JT6M usually used for VHF meteor scatter and the like. Well someone decided that it'd be fun to use it on 20m and you will here is slowly diddling along quite often around 14.075mhz Any problems and just ask us here and we'll help. Regards Toby MM0TOB NW Scotland (Outer Hebrides) ---Original Message--- From: w1...@ymail.com Date: 18/02/2010 00:13:55 To: digitalradio@yahoogroups.com Subject: [digitalradio] Introduction and question Greetings. I am Wes W1LIC in Bangor, ME and just joined this group. I run a Kenwood TS-480SAT to vertical or dipole antennas. I have an old HP desktop running XP and use either the FLDIGI or PSKExpress software. Although I've been a ham since 1967, I am a newbie to the digital modes. CW has always been my primary mode of operation. I've had several contacts via PSK31, but now am interested in trying other modes. This week I had my first contact via OLIVIA, which seems to be a very interesting mode. I've always heard and read that on PSK31 we should greatly reduce our power and not show any ALC indication when transmitting. Does this same advice hold true for Olivia and other digital modes as well? I'd appreciate input from some of you more experienced digital ops. Wes W1LIC 111.jpg111.gif
Re: [digitalradio]
Excellent, MANY thanks! On Wed, Feb 17, 2010 at 6:38 PM, Pieter pdeh...@vodafonevast.nl wrote: Good day guys The update is there. The January logs are implemented. For those who want to contribute (except UDXF members), send your logs (everything, included am broadcasting) to me postmas...@shortwavemonitor.com www.shortwavemonitor.com image001.gif
Re: [digitalradio] Re: Introduction and question
See Wes I knew someone much more technicly minded would come up with a wealth of information. Lol Good job Andy Toby mm0tob ---Original Message--- From: obrienaj Date: 18/02/2010 00:47:16 To: digitalradio@yahoogroups.com Subject: [digitalradio] Re: Introduction and question Welcome to the group, Wes. That is an interesting question, I look forward to seeing other answers. My answer is rather vague and generalized . I'm going to argue that reduced power is not really the issue, but that reduced power is often associated with no ALC which most point out is a key in not having a over-driven, distorted , signal . I say most because not every ham agrees with this, some thing ALC is not that much of a factor. The prevailing view is that most soundcard modes should not be showing ALC, PSK31-250, Olivia, AFSK ,RTTY, etc, but some modes like JT65A are less prone to this issue. FSK RTTY is also not a mode that would be impacted by this issue. Consider this from PSK Fundementals by Peter G3PLX (http://aintel.bi.ehu es/psk31theory.html). Also see http://www.eham.net/articles/12626 The Good Bad and Ugly on PSK31. There is a problem with PSK keying which doesn't show up with FSK, and that is the effect of key-clicks. We can get away with hard FSK keying at moderate baudrates without generating too much splatter, but polarity reversals are equivalent to simultaneous switching-off of one transmitter and switching-on of another one in antiphase: the result being keyclicks that are TWICE AS BAD as on-off keying, all other things being equal. So if we use computer logic to key a BPSK modulator such as an exclusive-or gate, at 31 baud, the emission would be extremely broad. In fact it would be about 3 times the baudrate wide at 10dB down, 5 times at 14dB down, 7 times at 17dB down, and so on (the squarewave Fourier series in fact) The solution is to filter the output, or to shape the envelope amplitude of each bit which amounts to the same thing. In PSK31, a cosine shape is used. To see what this does to the waveform and the spectrum, consider transmitting a sequence of continuous polarity-reversals at 31 baud. With cosine shaping, the envelope ends up looking like full-wave rectified 31Hz AC. This not only looks like a two-tone test signal, it IS a two-tone test signal, and the spectrum consists of two pure tones at +/-15Hz from the centre, and no splatter. Like the two-tone and unlike FSK, however, if we pass this through a transmitter, we get intermodulation products if it is not linear, so we DO need to be careful not to overdrive the audio. However, even the worst linears will give third-order products of 25dB at +/-47Hz (3 times the baudrate wide) and fifth-order products of 35dB at +/-78Hz (5 times the baudrate wide), a considerable improvement over the hard-keying case. If we infinitely overdrive the linear, we are back to the same levels as the hard-keyed system. Andy K3UK --- In digitalradio@yahoogroups.com, w1...@... w1...@... wrote: Greetings. I am Wes W1LIC in Bangor, ME and just joined this group. I run a Kenwood TS-480SAT to vertical or dipole antennas. I have an old HP desktop running XP and use either the FLDIGI or PSKExpress software. Although I've been a ham since 1967, I am a newbie to the digital modes. CW has always been my primary mode of operation. I've had several contacts via PSK31, but now am interested in trying other modes. This week I had my first contact via OLIVIA, which seems to be a very interesting mode. I've always heard and read that on PSK31 we should greatly reduce our power and not show any ALC indication when transmitting. Does this same advice hold true for Olivia and other digital modes as well? I'd appreciate input from some of you more experienced digital ops. Wes W1LIC 111.jpg111.gif
Re: [digitalradio]
I find the fact that Tunisian police are using Pactor 2, fascinating. 16.126,70 stat11 Tunsian police pactor-2 1415 12/01/10 send krypted mails to stat151 'defa...@#hfarq#stat11' 16.126,70 stat12 tunisian police pactor-2 1130 12/01/10 send krypted mails to stat151 'defa...@#hfarq#stat12' 16.126,70 stat151 tunesian police, tun pactor-2 0740 01/05/09 send krypted mails 'defa...@#hfarq#stat151' 16.126,70 stat154 tunesian police, tun pactor-2 0737 10/11/09 send krypted mails '#hfarq#stat154' 16.126,70 stat16 tunisian police pactor-2 1218 15/01/10 send krypted mails to stat151 'defa...@#hfarq#stat16' 16.126,70 stat5 tunesian police, tun pactor-2 0804 10/11/09 send krypted mails 'defa...@#hfarq#stat5' On Wed, Feb 17, 2010 at 7:47 PM, Andy obrien k3uka...@gmail.com wrote: Excellent, MANY thanks! On Wed, Feb 17, 2010 at 6:38 PM, Pieter pdeh...@vodafonevast.nl wrote: Good day guys The update is there. The January logs are implemented. For those who want to contribute (except UDXF members), send your logs (everything, included am broadcasting) to me postmas...@shortwavemonitor.com www.shortwavemonitor.com image001.gif
Re: [digitalradio] Re: Introduction and question
To bypass all the technical stuff: just listen to the PSK bands and watch for single stations which show up across the waterfall in numerous places. In most cases, it is because they are sending with too much power. Ask them to decrease power, and the extra upper/lower signals just disappear. Sometimes its difficult to figure outw here they are listening, due to so many strong signals from the same station.Like any other mode, one should always start out with the lowest possible signal, and if they dont answer, increase it a few watts and try try again. We are supposed to use the least power needed for a contact. Thats part of the Amateur operators code, isnt it? Danny Douglas N7DC ex WN5QMX ET2US WA5UKR ET3USA SV0WPP VS6DD N7DC/YV5 G5CTB All 2 years or more (except Novice). Short stints at: DA/PA/SU/HZ/7X/DU CR9/7Y/KH7/5A/GW/GM/F Pls QSL direct, buro, or LOTW preferred, I Do not use, but as a courtesy do upload to eQSL for those who do. Moderator DXandTALK http://groups.yahoo.com/group/DXandTalk Digital_modes http://groups.yahoo.com/group/digital_modes/?yguid=341090159 Danny Douglas N7DC ex WN5QMX ET2US WA5UKR ET3USA SV0WPP VS6DD N7DC/YV5 G5CTB All 2 years or more (except Novice). Short stints at: DA/PA/SU/HZ/7X/DU CR9/7Y/KH7/5A/GW/GM/F Pls QSL direct, buro, or LOTW preferred, I Do not use, but as a courtesy do upload to eQSL for those who do. Moderator DXandTALK http://groups.yahoo.com/group/DXandTalk Digital_modes http://groups.yahoo.com/group/digital_modes/?yguid=341090159 Danny Douglas N7DC ex WN5QMX ET2US WA5UKR ET3USA SV0WPP VS6DD N7DC/YV5 G5CTB All 2 years or more (except Novice). Short stints at: DA/PA/SU/HZ/7X/DU CR9/7Y/KH7/5A/GW/GM/F Pls QSL direct, buro, or LOTW preferred, I Do not use, but as a courtesy do upload to eQSL for those who do. Moderator DXandTALK http://groups.yahoo.com/group/DXandTalk Digital_modes http://groups.yahoo.com/group/digital_modes/?yguid=341090159 - Original Message - From: Toby Burnett To: digitalradio@yahoogroups.com Sent: Wednesday, February 17, 2010 7:51 PM Subject: Re: [digitalradio] Re: Introduction and question See Wes I knew someone much more technicly minded would come up with a wealth of information. Lol Good job Andy Toby mm0tob ---Original Message--- From: obrienaj Date: 18/02/2010 00:47:16 To: digitalradio@yahoogroups.com Subject: [digitalradio] Re: Introduction and question Welcome to the group, Wes. That is an interesting question, I look forward to seeing other answers. My answer is rather vague and generalized . I'm going to argue that reduced power is not really the issue, but that reduced power is often associated with no ALC which most point out is a key in not having a over-driven, distorted , signal . I say most because not every ham agrees with this, some thing ALC is not that much of a factor. The prevailing view is that most soundcard modes should not be showing ALC, PSK31-250, Olivia, AFSK ,RTTY, etc, but some modes like JT65A are less prone to this issue. FSK RTTY is also not a mode that would be impacted by this issue. Consider this from PSK Fundementals by Peter G3PLX (http://aintel.bi.ehu.es/psk31theory.html). Also see http://www.eham.net/articles/12626 The Good Bad and Ugly on PSK31. There is a problem with PSK keying which doesn't show up with FSK, and that is the effect of key-clicks. We can get away with hard FSK keying at moderate baudrates without generating too much splatter, but polarity reversals are equivalent to simultaneous switching-off of one transmitter and switching-on of another one in antiphase: the result being keyclicks that are TWICE AS BAD as on-off keying, all other things being equal. So if we use computer logic to key a BPSK modulator such as an exclusive-or gate, at 31 baud, the emission would be extremely broad. In fact it would be about 3 times the baudrate wide at 10dB down, 5 times at 14dB down, 7 times at 17dB down, and so on (the squarewave Fourier series in fact) The solution is to filter the output, or to shape the envelope amplitude of each bit which amounts to the same thing. In PSK31, a cosine shape is used. To see what this does to the waveform and the spectrum, consider transmitting a sequence of continuous polarity-reversals at 31 baud. With cosine shaping, the envelope ends up looking like full-wave rectified 31Hz AC. This not only looks like a two-tone test signal, it IS a two-tone test signal, and the spectrum consists of two pure tones at +/-15Hz from the centre, and no splatter. Like the two-tone and unlike FSK, however, if we pass this through a transmitter, we get intermodulation products if it is not linear, so we DO need to be careful not to overdrive the audio. However, even the worst linears will give third-order
