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software defined radios
anyone use SDRs?
i am looking at the Ciaoradio. it is 349 Euros, and i think it comes with the software. i may invest in the software alone at first. i would like an RFspace SDR, because it can record 160 khz band to hard drive. both that and the Gnuradio hardware are too expensive. i am using my sound card for DC to 22 khz reception. my Sony ICF2001 is doing poorly. i suspect there is corrosion in the potentiometers. and i may have blown out the front end somehow. i hear you can mess up a front end and the radio will still work, but you can't hear much of anything. my choices now a 1. repair the Yaesu transceiver 2. use the Yaesu FRG7 receiver 3. get a Sangean or Ciaoradio 4. focus on ELF with an Maudio card i'd love to have an SDR, but i still want to decode RTTY and do other things. so a gen purpose receiver may be easiest. Gravity |
software defined radios
Have ya looked at WinRadio's line?
"gravity" wrote in message reenews.net... anyone use SDRs? i am looking at the Ciaoradio. it is 349 Euros, and i think it comes with the software. i may invest in the software alone at first. i would like an RFspace SDR, because it can record 160 khz band to hard drive. both that and the Gnuradio hardware are too expensive. i am using my sound card for DC to 22 khz reception. my Sony ICF2001 is doing poorly. i suspect there is corrosion in the potentiometers. and i may have blown out the front end somehow. i hear you can mess up a front end and the radio will still work, but you can't hear much of anything. my choices now a 1. repair the Yaesu transceiver 2. use the Yaesu FRG7 receiver 3. get a Sangean or Ciaoradio 4. focus on ELF with an Maudio card i'd love to have an SDR, but i still want to decode RTTY and do other things. so a gen purpose receiver may be easiest. Gravity |
software defined radios
gravity wrote: anyone use SDRs? i am looking at the Ciaoradio. it is 349 Euros, and i think it comes with the software. i may invest in the software alone at first. i would like an RFspace SDR, because it can record 160 khz band to hard drive. both that and the Gnuradio hardware are too expensive. i am using my sound card for DC to 22 khz reception. my Sony ICF2001 is doing poorly. i suspect there is corrosion in the potentiometers. and i may have blown out the front end somehow. i hear you can mess up a front end and the radio will still work, but you can't hear much of anything. my choices now a 1. repair the Yaesu transceiver 2. use the Yaesu FRG7 receiver 3. get a Sangean or Ciaoradio 4. focus on ELF with an Maudio card i'd love to have an SDR, but i still want to decode RTTY and do other things. so a gen purpose receiver may be easiest. Gravity I think analog front end and RF DSP demo is the way to go. I wish the market would work more on such a product. I don't consider DSP in the analog to be the solution. I'd like to see a FFT panoramic display in the radio, or at least a port to feed it to a PC. |
software defined radios
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software defined radios
Tom wrote:
wrote: So I could make a short wave radio out of a laptop using this software? You can make an Extremely Low Frequency radio out of a computer, tunable across the bandwidth of its sound system. You could tune up to about 1/2 the sampling frequency of the sound systems analog-to-digital converter. Typical sample rates are 48kHz but high end systems go up to 192 kHz so the tuning range would be up to 24 kHz and 96 kHz respectively, provided the computer can execute the SDR DSP software fast enough. If you connected an antenna to the microphone input, you might hear something. To tune higher frequencies, you can use a conventional superhet receiver as a tunable downconverter, connecting its last IF (if higher than the computer's audio input range) to a fixed downconverter, e.g., from 455 kHz to 12 kHz. Err, Ummm, well, yeah, in THEORY you could. In practice you'll need to decouple your computer from the antenna pretty well. This means you'll need a very high Q antenna with a very low noise amplifier to isolate it, and a very well isolated DC supply to power the amplifier. If those things exist, you can build your very own VLF receiver from a sound card. In fact, if your sound card can manage a sample rate of at least 120 kSamples/second then you could use it to tune in WWVB at 60 kHz or perhaps the German equivalent at 77 kHz if you can manage to sample at twice that rate. Other than WWVB, I don't think much is still down there. The earth's ionosphere resonates at about 7 Hz if memory serves, so that might be a lower limit to what you might want to try monitoring. The Omega system was decommissioned years ago, though I've heard rumors that some parts of it might still be in service in some corners of the world. Finally, if there are any old FDM coaxial systems nearby, you might detect some leakage from their traffic (I doubt there are any who still use this method to trunk VF traffic together, but if there are a few, you might still hear it) And yes, a very few radios have a third IF at 50 kHz which you could use such a sound card with. That experiment has potential. 73, Jake Brodsky Amateur Radio Station AB3A |
software defined radios
Jake Brodsky wrote: Tom wrote: wrote: So I could make a short wave radio out of a laptop using this software? You can make an Extremely Low Frequency radio out of a computer, tunable across the bandwidth of its sound system. You could tune up to about 1/2 the sampling frequency of the sound systems analog-to-digital converter. Typical sample rates are 48kHz but high end systems go up to 192 kHz so the tuning range would be up to 24 kHz and 96 kHz respectively, provided the computer can execute the SDR DSP software fast enough. If you connected an antenna to the microphone input, you might hear something. To tune higher frequencies, you can use a conventional superhet receiver as a tunable downconverter, connecting its last IF (if higher than the computer's audio input range) to a fixed downconverter, e.g., from 455 kHz to 12 kHz. Err, Ummm, well, yeah, in THEORY you could. In practice you'll need to decouple your computer from the antenna pretty well. This means you'll need a very high Q antenna with a very low noise amplifier to isolate it, and a very well isolated DC supply to power the amplifier. If those things exist, you can build your very own VLF receiver from a sound card. In fact, if your sound card can manage a sample rate of at least 120 kSamples/second then you could use it to tune in WWVB at 60 kHz or perhaps the German equivalent at 77 kHz if you can manage to sample at twice that rate. Other than WWVB, I don't think much is still down there. The earth's ionosphere resonates at about 7 Hz if memory serves, so that might be a lower limit to what you might want to try monitoring. The Omega system was decommissioned years ago, though I've heard rumors that some parts of it might still be in service in some corners of the world. Finally, if there are any old FDM coaxial systems nearby, you might detect some leakage from their traffic (I doubt there are any who still use this method to trunk VF traffic together, but if there are a few, you might still hear it) And yes, a very few radios have a third IF at 50 kHz which you could use such a sound card with. That experiment has potential. 73, Jake Brodsky Amateur Radio Station AB3A Yeah, everything looks easy in theory. Computers are serious noise machines. You've probably seen this website: http://www.vlf.it/ Think of painting a room. Isn't 90% of the work the preparation? Well, in signal analysis, conditioning the signal is a serious chunk of the work. Once you have something clean, then digital analysis can be done. If you do build any of those designs on vlf.it, you may want to investigate better (lower noise) op amps. |
software defined radios
Jake Brodsky wrote:
Tom wrote: wrote: So I could make a short wave radio out of a laptop using this software? You can make an Extremely Low Frequency radio out of a computer, tunable across the bandwidth of its sound system. You could tune up to about 1/2 the sampling frequency of the sound systems analog-to-digital converter. Typical sample rates are 48kHz but high end systems go up to 192 kHz so the tuning range would be up to 24 kHz and 96 kHz respectively, provided the computer can execute the SDR DSP software fast enough. If you connected an antenna to the microphone input, you might hear something. To tune higher frequencies, you can use a conventional superhet receiver as a tunable downconverter, connecting its last IF (if higher than the computer's audio input range) to a fixed downconverter, e.g., from 455 kHz to 12 kHz. Err, Ummm, well, yeah, in THEORY you could. In practice you'll need to decouple your computer from the antenna pretty well. This means you'll need a very high Q antenna with a very low noise amplifier to isolate it, and a very well isolated DC supply to power the amplifier. If those things exist, you can build your very own VLF receiver from a sound card. In fact, if your sound card can manage a sample rate of at least 120 kSamples/second then you could use it to tune in WWVB at 60 kHz or perhaps the German equivalent at 77 kHz if you can manage to sample at twice that rate. [snip] And yes, a very few radios have a third IF at 50 kHz which you could use such a sound card with. That experiment has potential. 73, Jake Brodsky Amateur Radio Station AB3A The point of my message was that you cannot make a SW radio out of a laptop alone ( the question he asked) but could make a VLF receiver out of a laptop that could be used with a downconverter to tune SW. Many have done so. The downconverter is typically a superhet radio whose last IF is downconverted through an add-on to the audio frequency range. The audio frequency laptop receiver need not have especially high sampling frequency or sample size when used with a downconverter for SW. A 10 kHz wide passband is adequate for most transmission modes and is readily provided by a 48 kHz sample rate - even 24 kHz could be enough. Because the front end tuner has AGC and can regulate levels into the sound card, the latter's A/D converter having something approaching 16 bit resolution will have more than adequate dynamic range - even 8-bits could be sufficient. Of course, the state of the art is for higher resolution A/D converters and higher sampling rates for direct conversion for DSP. As discussed elsewhere, great care must be taken in controlling interference from the SDR to itself, via the antenna or other unintended coupling. Tom |
software defined radios
gravity wrote: it might make more sense to buy an off the shelf solution e.g. Ciaoradio, RFspace, or Gnu Radio. however it would be cool to homebrew the whole thing! Gravity 73, Jake Brodsky Amateur Radio Station AB3A Gravity, you really bring me down. |
software defined radios
"Tom" wrote:
The point of my message was that you cannot make a SW radio out of a laptop alone yes that was my question And now I'm clear on that...thanks! I've just been debating buying a small portable SW radio as I've gotten completely rid of TV and cable TV and thinking maybe SW radio might be a good replacement for it. Sounds like it best for me to get a dedicated stand lone small SW radio I mistakenly assumed I could put some software on my laptop and make a SW radio out it |
software defined radios
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software defined radios
Tom wrote: Jake Brodsky wrote: Tom wrote: wrote: So I could make a short wave radio out of a laptop using this software? You can make an Extremely Low Frequency radio out of a computer, tunable across the bandwidth of its sound system. You could tune up to about 1/2 the sampling frequency of the sound systems analog-to-digital converter. Typical sample rates are 48kHz but high end systems go up to 192 kHz so the tuning range would be up to 24 kHz and 96 kHz respectively, provided the computer can execute the SDR DSP software fast enough. If you connected an antenna to the microphone input, you might hear something. To tune higher frequencies, you can use a conventional superhet receiver as a tunable downconverter, connecting its last IF (if higher than the computer's audio input range) to a fixed downconverter, e.g., from 455 kHz to 12 kHz. Err, Ummm, well, yeah, in THEORY you could. In practice you'll need to decouple your computer from the antenna pretty well. This means you'll need a very high Q antenna with a very low noise amplifier to isolate it, and a very well isolated DC supply to power the amplifier. If those things exist, you can build your very own VLF receiver from a sound card. In fact, if your sound card can manage a sample rate of at least 120 kSamples/second then you could use it to tune in WWVB at 60 kHz or perhaps the German equivalent at 77 kHz if you can manage to sample at twice that rate. [snip] And yes, a very few radios have a third IF at 50 kHz which you could use such a sound card with. That experiment has potential. 73, Jake Brodsky Amateur Radio Station AB3A The point of my message was that you cannot make a SW radio out of a laptop alone ( the question he asked) but could make a VLF receiver out of a laptop that could be used with a downconverter to tune SW. Many have done so. The downconverter is typically a superhet radio whose last IF is downconverted through an add-on to the audio frequency range. The audio frequency laptop receiver need not have especially high sampling frequency or sample size when used with a downconverter for SW. A 10 kHz wide passband is adequate for most transmission modes and is readily provided by a 48 kHz sample rate - even 24 kHz could be enough. Because the front end tuner has AGC and can regulate levels into the sound card, the latter's A/D converter having something approaching 16 bit resolution will have more than adequate dynamic range - even 8-bits could be sufficient. Of course, the state of the art is for higher resolution A/D converters and higher sampling rates for direct conversion for DSP. As discussed elsewhere, great care must be taken in controlling interference from the SDR to itself, via the antenna or other unintended coupling. Tom All you are really doing is using the PC for the demod, which is technically not a software defined radio. Mind you it can be done, but it is really just an analog radio with some DSP. |
software defined radios
Tom wrote: wrote: Tom wrote: Jake Brodsky wrote: Tom wrote: wrote: So I could make a short wave radio out of a laptop using this software? You can make an Extremely Low Frequency radio out of a computer, tunable across the bandwidth of its sound system. You could tune up to about 1/2 the sampling frequency of the sound systems analog-to-digital converter. Typical sample rates are 48kHz but high end systems go up to 192 kHz so the tuning range would be up to 24 kHz and 96 kHz respectively, provided the computer can execute the SDR DSP software fast enough. If you connected an antenna to the microphone input, you might hear something. To tune higher frequencies, you can use a conventional superhet receiver as a tunable downconverter, connecting its last IF (if higher than the computer's audio input range) to a fixed downconverter, e.g., from 455 kHz to 12 kHz. Err, Ummm, well, yeah, in THEORY you could. In practice you'll need to decouple your computer from the antenna pretty well. This means you'll need a very high Q antenna with a very low noise amplifier to isolate it, and a very well isolated DC supply to power the amplifier. If those things exist, you can build your very own VLF receiver from a sound card. In fact, if your sound card can manage a sample rate of at least 120 kSamples/second then you could use it to tune in WWVB at 60 kHz or perhaps the German equivalent at 77 kHz if you can manage to sample at twice that rate. [snip] And yes, a very few radios have a third IF at 50 kHz which you could use such a sound card with. That experiment has potential. 73, Jake Brodsky Amateur Radio Station AB3A The point of my message was that you cannot make a SW radio out of a laptop alone ( the question he asked) but could make a VLF receiver out of a laptop that could be used with a downconverter to tune SW. Many have done so. The downconverter is typically a superhet radio whose last IF is downconverted through an add-on to the audio frequency range. The audio frequency laptop receiver need not have especially high sampling frequency or sample size when used with a downconverter for SW. A 10 kHz wide passband is adequate for most transmission modes and is readily provided by a 48 kHz sample rate - even 24 kHz could be enough. Because the front end tuner has AGC and can regulate levels into the sound card, the latter's A/D converter having something approaching 16 bit resolution will have more than adequate dynamic range - even 8-bits could be sufficient. Of course, the state of the art is for higher resolution A/D converters and higher sampling rates for direct conversion for DSP. As discussed elsewhere, great care must be taken in controlling interference from the SDR to itself, via the antenna or other unintended coupling. Tom All you are really doing is using the PC for the demod, which is technically not a software defined radio. Mind you it can be done, but it is really just an analog radio with some DSP. Technically, it is a VLF SDR with an analog downconverter. By itself, it can receive wireless energy, tunes over a spectrum of less than 1/2 the sample rate, has variable IF bandwidth, can demodulate many modes, does noise reduction, all through software. How is that not a software defined radio? Practical SDR's are going to have analog elements in them, if the modulation is to be interpreted by one's hearing. Tom In the strict sense, the SDRs are ADCs and massive DSP. You wouldn't have analog IFs because that restricts the BW of the signal. That is, nothing can be wider than the IF. A true SDR could demod multiple signals at one time. |
software defined radios
wrote: Tom wrote: wrote: Tom wrote: [snip] The point of my message was that you cannot make a SW radio out of a laptop alone ( the question he asked) but could make a VLF receiver out of a laptop that could be used with a downconverter to tune SW. Many have done so. The downconverter is typically a superhet radio whose last IF is downconverted through an add-on to the audio frequency range. The audio frequency laptop receiver need not have especially high sampling frequency or sample size when used with a downconverter for SW. A 10 kHz wide passband is adequate for most transmission modes and is readily provided by a 48 kHz sample rate - even 24 kHz could be enough. Because the front end tuner has AGC and can regulate levels into the sound card, the latter's A/D converter having something approaching 16 bit resolution will have more than adequate dynamic range - even 8-bits could be sufficient. Of course, the state of the art is for higher resolution A/D converters and higher sampling rates for direct conversion for DSP. As discussed elsewhere, great care must be taken in controlling interference from the SDR to itself, via the antenna or other unintended coupling. Tom All you are really doing is using the PC for the demod, which is technically not a software defined radio. Mind you it can be done, but it is really just an analog radio with some DSP. Technically, it is a VLF SDR with an analog downconverter. By itself, it can receive wireless energy, tunes over a spectrum of less than 1/2 the sample rate, has variable IF bandwidth, can demodulate many modes, does noise reduction, all through software. How is that not a software defined radio? Practical SDR's are going to have analog elements in them, if the modulation is to be interpreted by one's hearing. Tom In the strict sense, the SDRs are ADCs and massive DSP. You wouldn't have analog IFs because that restricts the BW of the signal. That is, nothing can be wider than the IF. A true SDR could demod multiple signals at one time. From Wikipedia and what looks like an authoritatively written article: "A software-defined radio (SDR) system is a radio communication system which uses software for the modulation and demodulation of radio signals." From the ARRL Technology Task Force Report 2001 http://www.arrl.org/announce/reports-01/tt.html: "Most software receivers have an analog front end consisting of band-pass filtering, a low-noise RF amplifier to set a low system noise level, a local oscillator and mixer to heterodyne the signal to an intermediate frequency (IF) where analog-to-digital (A/D) conversion, digital filtering and demodulation takes place. Recently, however, there are some software receivers that perform A/D conversion immediately after the antenna." Your "strict sense" and "true SDR" interpretations are much too narrow and illogical. that's like saying a radio is not a radio unless it can receive the highest possible frequency. A crystal radio is still a radio; a VLF software defined radio is very much a software defined radio whether it demodulates one or many signals. Neither needs to use state of the art technology to continue to be so defined. A notebook computer capable of demodulating via software a VLF radio signal coupled to its sound card input is therefore a radio receiver defined by software. Putting a downconverter in front of either the crystal radio or the software defined radio simply adds the adjective "superheterodyne" to their descriptors. These descriptors define the sub-classes of radios to which a particular implementation belongs; the sub-class of radios called software defined radios has many sub-classes of its own, including both purpose built hardware/software systems and general purpose hardware such as a personal computer running SDR software. Tom |
software defined radios
wrote: Tom wrote: wrote: Tom wrote: wrote: Tom wrote: [snip] The point of my message was that you cannot make a SW radio out of a laptop alone ( the question he asked) but could make a VLF receiver out of a laptop that could be used with a downconverter to tune SW. Many have done so. The downconverter is typically a superhet radio whose last IF is downconverted through an add-on to the audio frequency range. The audio frequency laptop receiver need not have especially high sampling frequency or sample size when used with a downconverter for SW. A 10 kHz wide passband is adequate for most transmission modes and is readily provided by a 48 kHz sample rate - even 24 kHz could be enough. Because the front end tuner has AGC and can regulate levels into the sound card, the latter's A/D converter having something approaching 16 bit resolution will have more than adequate dynamic range - even 8-bits could be sufficient. Of course, the state of the art is for higher resolution A/D converters and higher sampling rates for direct conversion for DSP. As discussed elsewhere, great care must be taken in controlling interference from the SDR to itself, via the antenna or other unintended coupling. Tom All you are really doing is using the PC for the demod, which is technically not a software defined radio. Mind you it can be done, but it is really just an analog radio with some DSP. Technically, it is a VLF SDR with an analog downconverter. By itself, it can receive wireless energy, tunes over a spectrum of less than 1/2 the sample rate, has variable IF bandwidth, can demodulate many modes, does noise reduction, all through software. How is that not a software defined radio? Practical SDR's are going to have analog elements in them, if the modulation is to be interpreted by one's hearing. Tom In the strict sense, the SDRs are ADCs and massive DSP. You wouldn't have analog IFs because that restricts the BW of the signal. That is, nothing can be wider than the IF. A true SDR could demod multiple signals at one time. From Wikipedia and what looks like an authoritatively written article: "A software-defined radio (SDR) system is a radio communication system which uses software for the modulation and demodulation of radio signals." From the ARRL Technology Task Force Report 2001 http://www.arrl.org/announce/reports-01/tt.html: "Most software receivers have an analog front end consisting of band-pass filtering, a low-noise RF amplifier to set a low system noise level, a local oscillator and mixer to heterodyne the signal to an intermediate frequency (IF) where analog-to-digital (A/D) conversion, digital filtering and demodulation takes place. Recently, however, there are some software receivers that perform A/D conversion immediately after the antenna." Your "strict sense" and "true SDR" interpretations are much too narrow and illogical. that's like saying a radio is not a radio unless it can receive the highest possible frequency. A crystal radio is still a radio; a VLF software defined radio is very much a software defined radio whether it demodulates one or many signals. Neither needs to use state of the art technology to continue to be so defined. A notebook computer capable of demodulating via software a VLF radio signal coupled to its sound card input is therefore a radio receiver defined by software. Putting a downconverter in front of either the crystal radio or the software defined radio simply adds the adjective "superheterodyne" to their descriptors. These descriptors define the sub-classes of radios to which a particular implementation belongs; the sub-class of radios called software defined radios has many sub-classes of its own, including both purpose built hardware/software systems and general purpose hardware such as a personal computer running SDR software. Tom Thirty years ago, that would qualify as a SDR. Look at the block diagram of what it takes today to be a SDR: http://www.monteriallc.com/downloads/Aquila.pdf Bandlimiting on the front end, then high resolution ADC, followed by DSP. This is not just DSP demod. A radio is a radio, whether it is a crystal radio, a regenerative one, a superhet, single, double, triple conversion. A software defined radio is a software defined radio whether it receives VLF only or operates into the microwave region. Your example is a "HF Wideband SDR" and the way you talk, pretty soon it, too, will not "qualify as a SDR". How can it qualify one year and not another? Its block diagram is functionally similar to that of the PC running SDRadio softwa bandlimited front end (anti-alias filter), ADC (16 bits to 24 bits depending on sound card, therefore greater dynamic range than your 14 bit example), followed by DSP software. So what if it's a general purpose CPU running DSP software or a DSP IC - it's still DSP, just different levels of performance. Now if you were to substitute "state-of-the-art SDR" wherever you said "SDR" in your last message, I'd agree with you, except SDRadio and Dream are not "just DSP demod" - they also filter before demod and do noise reduction and AVC. [30] Tom |
software defined radios
Tom wrote: wrote: Tom wrote: wrote: Tom wrote: wrote: Tom wrote: [snip] The point of my message was that you cannot make a SW radio out of a laptop alone ( the question he asked) but could make a VLF receiver out of a laptop that could be used with a downconverter to tune SW. Many have done so. The downconverter is typically a superhet radio whose last IF is downconverted through an add-on to the audio frequency range. The audio frequency laptop receiver need not have especially high sampling frequency or sample size when used with a downconverter for SW. A 10 kHz wide passband is adequate for most transmission modes and is readily provided by a 48 kHz sample rate - even 24 kHz could be enough. Because the front end tuner has AGC and can regulate levels into the sound card, the latter's A/D converter having something approaching 16 bit resolution will have more than adequate dynamic range - even 8-bits could be sufficient. Of course, the state of the art is for higher resolution A/D converters and higher sampling rates for direct conversion for DSP. As discussed elsewhere, great care must be taken in controlling interference from the SDR to itself, via the antenna or other unintended coupling. Tom All you are really doing is using the PC for the demod, which is technically not a software defined radio. Mind you it can be done, but it is really just an analog radio with some DSP. Technically, it is a VLF SDR with an analog downconverter. By itself, it can receive wireless energy, tunes over a spectrum of less than 1/2 the sample rate, has variable IF bandwidth, can demodulate many modes, does noise reduction, all through software. How is that not a software defined radio? Practical SDR's are going to have analog elements in them, if the modulation is to be interpreted by one's hearing. Tom In the strict sense, the SDRs are ADCs and massive DSP. You wouldn't have analog IFs because that restricts the BW of the signal. That is, nothing can be wider than the IF. A true SDR could demod multiple signals at one time. From Wikipedia and what looks like an authoritatively written article: "A software-defined radio (SDR) system is a radio communication system which uses software for the modulation and demodulation of radio signals." From the ARRL Technology Task Force Report 2001 http://www.arrl.org/announce/reports-01/tt.html: "Most software receivers have an analog front end consisting of band-pass filtering, a low-noise RF amplifier to set a low system noise level, a local oscillator and mixer to heterodyne the signal to an intermediate frequency (IF) where analog-to-digital (A/D) conversion, digital filtering and demodulation takes place. Recently, however, there are some software receivers that perform A/D conversion immediately after the antenna." Your "strict sense" and "true SDR" interpretations are much too narrow and illogical. that's like saying a radio is not a radio unless it can receive the highest possible frequency. A crystal radio is still a radio; a VLF software defined radio is very much a software defined radio whether it demodulates one or many signals. Neither needs to use state of the art technology to continue to be so defined. A notebook computer capable of demodulating via software a VLF radio signal coupled to its sound card input is therefore a radio receiver defined by software. Putting a downconverter in front of either the crystal radio or the software defined radio simply adds the adjective "superheterodyne" to their descriptors. These descriptors define the sub-classes of radios to which a particular implementation belongs; the sub-class of radios called software defined radios has many sub-classes of its own, including both purpose built hardware/software systems and general purpose hardware such as a personal computer running SDR software. Tom Thirty years ago, that would qualify as a SDR. Look at the block diagram of what it takes today to be a SDR: http://www.monteriallc.com/downloads/Aquila.pdf Bandlimiting on the front end, then high resolution ADC, followed by DSP. This is not just DSP demod. A radio is a radio, whether it is a crystal radio, a regenerative one, a superhet, single, double, triple conversion. A software defined radio is a software defined radio whether it receives VLF only or operates into the microwave region. Your example is a "HF Wideband SDR" and the way you talk, pretty soon it, too, will not "qualify as a SDR". How can it qualify one year and not another? Its block diagram is functionally similar to that of the PC running SDRadio softwa bandlimited front end (anti-alias filter), ADC (16 bits to 24 bits depending on sound card, therefore greater dynamic range than your 14 bit example), followed by DSP software. So what if it's a general purpose CPU running DSP software or a DSP IC - it's still DSP, just different levels of performance. Now if you were to substitute "state-of-the-art SDR" wherever you said "SDR" in your last message, I'd agree with you, except SDRadio and Dream are not "just DSP demod" - they also filter before demod and do noise reduction and AVC. [30] Tom The ARRL decided to call DSP demod being all that is required to have a SDR. The military, which pioneered the concept, at least had digital filters in the IF for their SDRs. |
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