Re: [Flexradio] 16 versus 24 bit audio
From G3PLX: Alberto: Thanks! That's the information I was seeking. It looks as if I was half-right, if there are, at best, 18 good bits in a 24-bit card. As Phil says, if 16-bit cards turn out to be worse that 16-bits, then there is some reason to go for a 24-bit card (which is worse than 24bits!). But for sure, 24 bit cards are not going to be 256-times (48dB, 8-bits) better than 16-bit cards. I will now continue working to convert my own 16-bit SDR code to 24-bits, but I think I will add a button on the front panel which zaps the bottom 8 bits. It will be VERY interesting to see if it makes any difference. To take Frank's point, as far as I can see from both the ASIO and WMME interfaces, there IS an accessible point in the software where this can be done before the audio data becomes floating-point. Thanks to all who replied. 73 Peter ___ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archive Link: http://mail.flex-radio.biz/pipermail/flexradio_flex-radio.biz/ FlexRadio Homepage: http://www.flex-radio.com
Re: [Flexradio] 16 versus 24 bit audio
Peter, One subtlety that was mentioned once but not emphasized very much is that some of what you may be seeing as noise is actually deliberate dithering in the card, which has the effect of pushing quantization noise out to inaudible frequencies. 8-bits seems a bit much for dithering to me, but still, a perfect non-dithering card, i.e., one that outputs a pure string of '0's for a shorted input, is arguably _worse_ than a dithering card that outputs a controlled spectrum of noise on shorted input. It can all get rather weird when there are non-linear, low S/S+N psychoacoustic detectors at the end of the chain, i.e., ears. Chris - AE6VK -Original Message- From: Peter Martinez [mailto:[EMAIL PROTECTED] Sent: Friday, May 19, 2006 11:20 PM To: Flex Reflector Subject: Re: [Flexradio] 16 versus 24 bit audio From G3PLX: Alberto: Thanks! That's the information I was seeking. It looks as if I was half-right, if there are, at best, 18 good bits in a 24-bit card. As Phil says, if 16-bit cards turn out to be worse that 16-bits, then there is some reason to go for a 24-bit card (which is worse than 24bits!). But for sure, 24 bit cards are not going to be 256-times (48dB, 8-bits) better than 16-bit cards. I will now continue working to convert my own 16-bit SDR code to 24-bits, but I think I will add a button on the front panel which zaps the bottom 8 bits. It will be VERY interesting to see if it makes any difference. To take Frank's point, as far as I can see from both the ASIO and WMME interfaces, there IS an accessible point in the software where this can be done before the audio data becomes floating-point. Thanks to all who replied. 73 Peter ___ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archive Link: http://mail.flex-radio.biz/pipermail/flexradio_flex-radio.biz/ FlexRadio Homepage: http://www.flex-radio.com ___ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archive Link: http://mail.flex-radio.biz/pipermail/flexradio_flex-radio.biz/ FlexRadio Homepage: http://www.flex-radio.com
Re: [Flexradio] 16 versus 24 bit audio
From G3PLX: Chris: I wondered about dithering. If I understand the idea, they introduce some deliberate noise in the ANALOGUE part of the ADC in order to spread the spectrum of any quantisation noise. Without it, I can imagine a tiny sinewave input of, say, one bit amplitude, looking to the software like a one-bit squarewave, with 3rd, 5th, ... harmonics. Dithering the analogue input would add a little noise to the fundamental sinewave but push the harmonics down. But, as you say, surely they would only introduce about one bit's worth of dither noise, not eight? 6dB not 48dB? I just did some proper measurements on the Firebox. On runs of 1200 samples at 48kHz, the r.m.s. noise level on the line input is about 400. It's about 450 on the Mike input. I did this by squaring each sample, summing these, dividing by 1200, and taking the square root. At the same time I calculated the DC level, just to make sure that was a lot smaller and didn't confuse things. This is about 9 bits of noise, or more if you suppose the peaks are higher. On the built-in 16-bit card in this laptop the DC level is 15 and I am not sure how to allow for this in the r.m.s calculation, but only the lsb toggles randomly. The MP3+ is the same, unless I select the mike input when the rms noise level is about 10. These figures are what I would have expected intuitively. One would expect the analogue noise-level to be roughly the same as the quantisation noise, in the same way that one would optimise any receiver so that all sources of noise contribute more-or-less the same in order to maximise the dynamic range. Intuitively I would have expected a 24-bit card to do the same, but maybe I am being naive. These measurements, and the figure quoted by Alberto, tells me that the 24-bit figure in the spec. is to some extent a marketting ploy. I can imagine a scenario where the designer of a new soundcard measured that it only gave 18 bits of useful data, so he decides to mask the data to 18-bits and sell it as an 18-bit card. The marketting manager of the company would surely override him, especially if the competition were all actively marketting so-called 24bit cards! 73 Peter ___ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archive Link: http://mail.flex-radio.biz/pipermail/flexradio_flex-radio.biz/ FlexRadio Homepage: http://www.flex-radio.com
Re: [Flexradio] 16 versus 24 bit audio
Peter, I asked the same question in a different way a while back. I noticed that with no inputs to the Firebox (or Delta 44 - I have both) the analogue input meters on the SDR software were reading in the order of 100dB down on maximum. Doing some simple maths the theoretical minimum fro a 24bit sample is 145dB down so where is the other 45dB of noise coming from? I may be over simplifying things but something doesn't seem right? As for dithering I read an article recently (maybe from Analog devices - can't remember) and do remember them talking about 1bit dithering. What I was trying to ascertain is whether there is a hardware issue or if it's a software issue (conscious design decision or otherwise). Apologies that this hasn't helped answer anything, but at least one other on the group is asking the same question! Regards, Paul M1PAF -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Peter Martinez Sent: 20 May 2006 10:07 To: Flex Reflector Subject: Re: [Flexradio] 16 versus 24 bit audio From G3PLX: Chris: I wondered about dithering. If I understand the idea, they introduce some deliberate noise in the ANALOGUE part of the ADC in order to spread the spectrum of any quantisation noise. Without it, I can imagine a tiny sinewave input of, say, one bit amplitude, looking to the software like a one-bit squarewave, with 3rd, 5th, ... harmonics. Dithering the analogue input would add a little noise to the fundamental sinewave but push the harmonics down. But, as you say, surely they would only introduce about one bit's worth of dither noise, not eight? 6dB not 48dB? I just did some proper measurements on the Firebox. On runs of 1200 samples at 48kHz, the r.m.s. noise level on the line input is about 400. It's about 450 on the Mike input. I did this by squaring each sample, summing these, dividing by 1200, and taking the square root. At the same time I calculated the DC level, just to make sure that was a lot smaller and didn't confuse things. This is about 9 bits of noise, or more if you suppose the peaks are higher. On the built-in 16-bit card in this laptop the DC level is 15 and I am not sure how to allow for this in the r.m.s calculation, but only the lsb toggles randomly. The MP3+ is the same, unless I select the mike input when the rms noise level is about 10. These figures are what I would have expected intuitively. One would expect the analogue noise-level to be roughly the same as the quantisation noise, in the same way that one would optimise any receiver so that all sources of noise contribute more-or-less the same in order to maximise the dynamic range. Intuitively I would have expected a 24-bit card to do the same, but maybe I am being naive. These measurements, and the figure quoted by Alberto, tells me that the 24-bit figure in the spec. is to some extent a marketting ploy. I can imagine a scenario where the designer of a new soundcard measured that it only gave 18 bits of useful data, so he decides to mask the data to 18-bits and sell it as an 18-bit card. The marketting manager of the company would surely override him, especially if the competition were all actively marketting so-called 24bit cards! 73 Peter ___ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archive Link: http://mail.flex-radio.biz/pipermail/flexradio_flex-radio.biz/ FlexRadio Homepage: http://www.flex-radio.com ___ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archive Link: http://mail.flex-radio.biz/pipermail/flexradio_flex-radio.biz/ FlexRadio Homepage: http://www.flex-radio.com
Re: [Flexradio] 16 versus 24 bit audio
From G3PLX: Thanks Paul. Thank goodness I am not alone! I just did a simple calculation. The ultimate rock-bottom noise power is kTB, where k is Boltzmann's constant (1.38e-23), T is room temperature (300 degrees K) and B is the bandwidth in which you measure it - let's say 24kHz for a 48kHz soundcard, so this works out to 1e-16 watts. Let's say the circuit is 600 ohms (just so we can get some idea of the picture), so the r.m.s. noise level across a 600 ohm source connected to a soundcard is going to be the square root of 600e-16, or 0.244uV. Again, just for the sake of it, let's say the soundcard ADC is designed for 2.2 volts peak-to-peak (that's 0dBm in 600 ohms). A 24-bit ADC would then give 2.2/(2^32) volts quantisation level. That comes out to 0.13uV. That's not far off the circuit noise level. That 'feels' about right to me. It says that an 'ideal' 24-bit soundcard should just be able to 'hear' it's own input noise. This is how we have always designed the front-ends of things! I am just throwing numbers in there, and the experts may say that the circuit isn't 600 ohm, or I haven't taken into account the noise factor of the pre-amp, or the typical ADC full-scale isn't 2.2 volts. But I am surely not wrong by a factor of 256? Where is all the noise coming from? Paul's observation that the noise is 100dB down on full-scale could just mean that there is that much noise coming from the SDR1000 RF hardware, but it would be easy to test this by unplugging it and short-circuiting the soundcard input. If the noise stays at the -100dB mark then it says the soundcard is that noisy, which is exactly what I find here with the Firebox. Maybe Paul has already done this. Note that the software measuring the noise needs to be set to the full soundcard bandwidth for this to make sense - it will look a lot cleaner if you select a narrow filter. I am not familiar with the SDR software so I don't know how this works. 73 Peter ___ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archive Link: http://mail.flex-radio.biz/pipermail/flexradio_flex-radio.biz/ FlexRadio Homepage: http://www.flex-radio.com
Re: [Flexradio] 16 versus 24 bit audio
Sorry Peter - should have said - these figures are with SDR hardware turned off and unplugged/inputs shorted out. -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Peter Martinez Sent: 20 May 2006 11:51 To: Flex Reflector Subject: Re: [Flexradio] 16 versus 24 bit audio From G3PLX: Thanks Paul. Thank goodness I am not alone! I just did a simple calculation. The ultimate rock-bottom noise power is kTB, where k is Boltzmann's constant (1.38e-23), T is room temperature (300 degrees K) and B is the bandwidth in which you measure it - let's say 24kHz for a 48kHz soundcard, so this works out to 1e-16 watts. Let's say the circuit is 600 ohms (just so we can get some idea of the picture), so the r.m.s. noise level across a 600 ohm source connected to a soundcard is going to be the square root of 600e-16, or 0.244uV. Again, just for the sake of it, let's say the soundcard ADC is designed for 2.2 volts peak-to-peak (that's 0dBm in 600 ohms). A 24-bit ADC would then give 2.2/(2^32) volts quantisation level. That comes out to 0.13uV. That's not far off the circuit noise level. That 'feels' about right to me. It says that an 'ideal' 24-bit soundcard should just be able to 'hear' it's own input noise. This is how we have always designed the front-ends of things! I am just throwing numbers in there, and the experts may say that the circuit isn't 600 ohm, or I haven't taken into account the noise factor of the pre-amp, or the typical ADC full-scale isn't 2.2 volts. But I am surely not wrong by a factor of 256? Where is all the noise coming from? Paul's observation that the noise is 100dB down on full-scale could just mean that there is that much noise coming from the SDR1000 RF hardware, but it would be easy to test this by unplugging it and short-circuiting the soundcard input. If the noise stays at the -100dB mark then it says the soundcard is that noisy, which is exactly what I find here with the Firebox. Maybe Paul has already done this. Note that the software measuring the noise needs to be set to the full soundcard bandwidth for this to make sense - it will look a lot cleaner if you select a narrow filter. I am not familiar with the SDR software so I don't know how this works. 73 Peter ___ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archive Link: http://mail.flex-radio.biz/pipermail/flexradio_flex-radio.biz/ FlexRadio Homepage: http://www.flex-radio.com ___ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archive Link: http://mail.flex-radio.biz/pipermail/flexradio_flex-radio.biz/ FlexRadio Homepage: http://www.flex-radio.com
Re: [Flexradio] 16 versus 24 bit audio
Hi Peter, Let me assure you: 24 bits is better than 16. Exactly how much better obviously depends on lots of things. And 16 bits would indeed be plenty if there were 16-bit sound cards that could actually deliver that resolution. If your low 8 bits are truly random with no input, that's a good thing! It follows that when you inject a non-random signal, it will stand out clearly from white noise. If the ADC resolution is good enough, this will also work at extremely low input levels i.e. when the S/N ratio is negative. Everyone, please read the specs of your sound cards. I don't have the PreSonus, but I have been using the 24-bit Delta 44 for years, already before there was SDR-1000. The input dynamic range for Delta 44 is only 99 dB(A). Of course, dynamic range does not necessarily translate to effective number of bits. Nevertheless, if we calculate ENOB using this value, we get ENOB = (99 - 1.76) / 6.02 = 16.2 bits. Then, there's also the dB(A) issue. Using A-weighting for audio applications may (or may not) make some sense, but for SDR-1000 it generally does not. For example, it looks like my Delta 44 has been tweaked to give optimal noise performace between 1-10 kHz. Above 10 kHz it's several dB's worse. Which is a problem because the PowerSDR software uses a 11.25 kHz IF. 73, Sami OH2BFO ___ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archive Link: http://mail.flex-radio.biz/pipermail/flexradio_flex-radio.biz/ FlexRadio Homepage: http://www.flex-radio.com
Re: [Flexradio] 16 versus 24 bit audio
On 5/20/06, Sami Aintila [EMAIL PROTECTED] wrote: software uses a 11.25 kHz IF. Ehm... correction: that's 11.025 kHz. ___ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archive Link: http://mail.flex-radio.biz/pipermail/flexradio_flex-radio.biz/ FlexRadio Homepage: http://www.flex-radio.com
Re: [Flexradio] 16 versus 24 bit audio
On 5/20/06, Peter Martinez [EMAIL PROTECTED] wrote: from G3PLX: Hello Sami. Thanks for joining the discussion - I feared I was on my own for a while! I hope some others will contribute too, so I don't get accused of hogging the bandwidth (or perhaps generating too much noise!). You said: If your low 8 bits are truly random with no input, that's a good thing! It follows that when you inject a non-random signal, it will stand out clearly from white noise. Let me be simple-minded and respond:- But if my low 8 bits are truly random and I inject an 8-bit sinewave, isn't it then level with the noise? If I could reduce my 8 bits of added noise to, say, 4 bits, wouldn't my sinewave then be 24dB above the noise? I don't see how adding that much noise can ever be a good thing to do. I am not trying to trap you, I really would like to understand what's going on here. This is all new stuff to me. I had a private email from a broadcast engineer who confirmed what I was saying about dither noise. He said they added 0.5 bits-worth of white noise to the analogue signal before digitisation, and subjectively that was the best result. But that's half a bit of dither, not 8 bits. 73 Peter Really, its like we are continuing to beat a dead horse here... a 24 bit card is not going to give you the theoretical 24 bits of resolution, just like a 16 bit card does not necessarily give you its theoretical 16 bits of resolution. Now some 16 bit cards can come close, but most 24 bit cards under $1000 are really going to give you 18 ENOB. Go back and do a search of the Flex Forum... there are examples of so called 24 bit cards that are much worse than some of the better 16 bit cards. When they say 16 bits or 24 bits, the manufacturers are refering to the ADCs rated resolution stated by its manufacturer. The design of the ADC front end, board layout, power supply filtering, etc... determines whether the board will even come close to the ADC rated specs (which are sometimes very optimistic in the first place). The Delta 44 became the recommended card for the SDR-1000 for a long time because in its price range, its performance was good, it has two ins and two outs, and ASIO drivers were available for it. Phil Harmon has just completed testing of the AKC ADC in the JANUS ADC/DAC board. He is seeing great numbers... this is the ADC used in one of the $1000 cards. We are not going to see 24 bits, but it will be much better than the Delta 44 or the Firebox. 73 de Phil N8VB ___ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archive Link: http://mail.flex-radio.biz/pipermail/flexradio_flex-radio.biz/ FlexRadio Homepage: http://www.flex-radio.com
Re: [Flexradio] 16 versus 24 bit audio
On 5/20/06, Philip Covington [EMAIL PROTECTED] wrote: On 5/20/06, Peter Martinez [EMAIL PROTECTED] wrote: from G3PLX: Hello Sami. Thanks for joining the discussion - I feared I was on my own for a while! I hope some others will contribute too, so I don't get accused of hogging the bandwidth (or perhaps generating too much noise!). You said: If your low 8 bits are truly random with no input, that's a good thing! It follows that when you inject a non-random signal, it will stand out clearly from white noise. Let me be simple-minded and respond:- But if my low 8 bits are truly random and I inject an 8-bit sinewave, isn't it then level with the noise? If I could reduce my 8 bits of added noise to, say, 4 bits, wouldn't my sinewave then be 24dB above the noise? I don't see how adding that much noise can ever be a good thing to do. I am not trying to trap you, I really would like to understand what's going on here. This is all new stuff to me. I had a private email from a broadcast engineer who confirmed what I was saying about dither noise. He said they added 0.5 bits-worth of white noise to the analogue signal before digitisation, and subjectively that was the best result. But that's half a bit of dither, not 8 bits. 73 Peter Really, its like we are continuing to beat a dead horse here... a 24 bit card is not going to give you the theoretical 24 bits of resolution, just like a 16 bit card does not necessarily give you its theoretical 16 bits of resolution. Now some 16 bit cards can come close, but most 24 bit cards under $1000 are really going to give you 18 ENOB. Go back and do a search of the Flex Forum... there are examples of so called 24 bit cards that are much worse than some of the better 16 bit cards. When they say 16 bits or 24 bits, the manufacturers are refering to the ADCs rated resolution stated by its manufacturer. The design of the ADC front end, board layout, power supply filtering, etc... determines whether the board will even come close to the ADC rated specs (which are sometimes very optimistic in the first place). The Delta 44 became the recommended card for the SDR-1000 for a long time because in its price range, its performance was good, it has two ins and two outs, and ASIO drivers were available for it. Phil Harmon has just completed testing of the AKC ADC in the JANUS ADC/DAC board. He is seeing great numbers... this is the ADC used in one of the $1000 cards. We are not going to see 24 bits, but it will be much better than the Delta 44 or the Firebox. 73 de Phil N8VB P.S. I was so jaded by all this ADC bit stuff that when discussions were going on in the old Xylo group about which ADC to use, I lobbied hard for the TI PCM4202 since it was easy to get compared to the AKM AK5394A part and I was convinced that the performance would not be all that much better. Well, I was definitely wrong about that one... this came out in testing... A few very smart individuals were suggesting all along that we look at the AKM part. I am glad that Phil VK6APH and Bill KD5TFD continued to test all possibilities... 73 de Phil N8VB ___ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archive Link: http://mail.flex-radio.biz/pipermail/flexradio_flex-radio.biz/ FlexRadio Homepage: http://www.flex-radio.com
Re: [Flexradio] 16 versus 24 bit audio
Peter Martinez wrote: snip Where is all the noise coming from? Paul's observation that the noise is 100dB down on full-scale could just mean that there is that much noise coming from the SDR1000 RF hardware, but it would be easy to test this by unplugging it and short-circuiting the soundcard input. If the noise stays at the -100dB mark then it says the soundcard is that noisy, which is exactly what I find here with the Firebox. Maybe Paul has already done this. Note that the software measuring the noise needs to be set to the full soundcard bandwidth for this to make sense - it will look a lot cleaner if you select a narrow filter. - snip - Yes, this last sentence is very important. When you evaluate the noise level on a spectrum display, don't forget that you are evaluating it in a bandwidth equal to the FFT bin size. And you can see it easily for yourself. If the program allows for this, change the bin size, e.g. make it half, and the base level of noise will drop by 3 dB... 73 Alberto I2PHD ___ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archive Link: http://mail.flex-radio.biz/pipermail/flexradio_flex-radio.biz/ FlexRadio Homepage: http://www.flex-radio.com
Re: [Flexradio] Henry 3K Classic SDR-1000
Thanks for all the replies on this. Larry, thanks for making the measurements on yours. That confirms that mine has apparently been fried, as it measures about 25 ohms keyed or not, and I do have the X2 sequencing checked in setup. I suspect RF must have gotten into my isolation box, as I was not connected directly to the Henry key jack from the SDR. Initially I had a boat load of RF in the shack until I found the problem. By then it was too late, and it quit keying. Oh well, in the meantime I will operate with a switch. Anyone know what I need to do to make the repair to the ULN2003A circuit? Thanks again for the help! Brian On 5/19/06, Larry Taft [EMAIL PROTECTED] wrote: Brian, I just made some measurements on my SDR-1000 with the power OFF. X2-pin7, reads infinite resistance using a digital multimeter. In the Diode test position with plus to pin 7 and minus to ground it shows open circuit. With the leads reversed minus to pin 7 the reading is 540 millivolts. This is consistent with the ULN2003A circuit which has a transistor open collector from pin 7 and the emitter to ground. Also a diode cathode pin 7 with anode to ground. You should get the same readings measuring pins 1 through 6 to ground as these are all the same kind of circuit. Unfortunately pins 1 through 6 don't have the external amplifier sequencing delay so tring to use one of these will result in hot switching the amp relay. For now I'd use a foot switch on the amp to turn it on just before you PTT the SDR. One man band sort of thing but it will work as I have done it here with my Drake L-4 before I got the FET isolated keying module from N0XAS. I put a back diode in my L-4 as I use it with several other radios. I also looked in the manual for my Henry 2K and it shows there is NO back diode for the changeover relay. There aren't any voltage values for the relay so I'm guessing its a 24 volt coil that draws 50 mills or so when operated. Measure the open circuit voltage of the Henry at the RCA jack and then use the milliamp meter to check the coil current. When the relay keing circuit is opened to turn the relay off you can get over 400 volt spike on the control line. This can cause failure of the X2-7 transistor. Haven't run the Henry in years. Its gained way too much weight just sitting in my office. 73, Larry K2LT Brian Sherrod wrote: I just hooked up my SDR to my Henry 3K Classic. I used pin 7 and pin 15 (grnd) on the X2 connector to cause the relay to go to ground, however something is wrong. If I use my ohmmeter between 7 and 15 without being keyed, I am seeing about 40 ohms, and when I key the SDR, it does not change. I can transmit on the Henry, but the ant relay does not switch back so that I can receive without pressing the standby switch on the amp. The amp only requires grounding the center pin on the rca jack, which is what I thought a connection of pin 7 15 would do on keyup of the SDR. Any suggestions appreciated. Brian / w5ami ___ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archive Link: http://mail.flex-radio.biz/pipermail/flexradio_flex-radio.biz/ FlexRadio Homepage: http://www.flex-radio.com
Re: [Flexradio] Henry 3K Classic SDR-1000
Brian, What is in the isolation box? I'm always looking for ways to do the control keying and changeover functions. As far as repair of the ULN2003A goes, I recommend sending the SDR back to Flex as it is all surface mount stuff on the board. They are skilled, reasonably priced and fast. Three out of three is good! Just had my SDR-1000 in for upgrades and repair. 73, Larry K2LT Brian Sherrod wrote: Thanks for all the replies on this. Larry, thanks for making the measurements on yours. That confirms that mine has apparently been fried, as it measures about 25 ohms keyed or not, and I do have the X2 sequencing checked in setup. I suspect RF must have gotten into my isolation box, as I was not connected directly to the Henry key jack from the SDR. Initially I had a boat load of RF in the shack until I found the problem. By then it was too late, and it quit keying. ___ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archive Link: http://mail.flex-radio.biz/pipermail/flexradio_flex-radio.biz/ FlexRadio Homepage: http://www.flex-radio.com
Re: [Flexradio] Henry 3K Classic SDR-1000
On 5/20/06, Larry Taft [EMAIL PROTECTED] wrote: Brian, What is in the isolation box? I'm always looking for ways to do the control keying and changeover functions. Nothing more than a tiny 12v relay I was keying by grounding from pin 7 15 with diode protection. As far as repair of the ULN2003A goes, I recommend sending the SDR back to Flex as it is all surface mount stuff on the board. They are skilled, reasonably priced and fast. Three out of three is good! Just had my SDR-1000 in for upgrades and repair. Okay Larry, thanks for that info! 73 Brian / w5ami ___ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archive Link: http://mail.flex-radio.biz/pipermail/flexradio_flex-radio.biz/ FlexRadio Homepage: http://www.flex-radio.com
[Flexradio] Dayton
Things are pretty interesting at Dayton, I met some of the Flex gang. I was looking for a HP signal generator but the prices are outrageous so I skipped buying one. My plans were that shortly after Dayton I would purchase a SDR-1000, but since I could not purchase the signal generator, and they had SDR-1000's in stock, I went ahead and purchased one. This was late yesterday as Dayton was closing so I dind't have a chance to purchase a small power supply and cables so I can play with it while on vacation. That will be taken care of shortly when I head for the bone yard. The weather yesterday was cloudy in the morning and sunny after 10:00AM, today is sunny also but it might rain in the afternoon. See ya in the funny papers. -- Cecil KD5NWA www.qrpradio.com ___ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archive Link: http://mail.flex-radio.biz/pipermail/flexradio_flex-radio.biz/ FlexRadio Homepage: http://www.flex-radio.com
Re: [Flexradio] Henry 3K Classic SDR-1000
Brian, How is the diode connected in the iso box? I've made the mistake of putting it across the key line when it really has to be across the coil of the relay to suppress the back EMF of the coil. Even the little 12 volt coils produce a wallop when the circuit is opened. If you have a 10X high impedance probe and a scope you can see the back voltage is a big number without the diode even with small coils. I'm familiar with RF loose in the shack. I burned out the input to my Tek 2712 spectrum analyzer a few years ago. Cost me $2200 to get it fixed as I need it for my broadcast measuring business. Has to have traceable calibration to be legal for the measurements so I had to pay the shot to Tek for the repairs. 73, Larry K2LT Brian Sherrod wrote: On 5/20/06, Larry Taft [EMAIL PROTECTED] wrote: Brian, What is in the isolation box? I'm always looking for ways to do the control keying and changeover functions. Nothing more than a tiny 12v relay I was keying by grounding from pin 7 15 with diode protection. As far as repair of the ULN2003A goes, I recommend sending the SDR back to Flex as it is all surface mount stuff on the board. They are skilled, reasonably priced and fast. Three out of three is good! Just had my SDR-1000 in for upgrades and repair. Okay Larry, thanks for that info! 73 Brian / w5ami ___ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archive Link: http://mail.flex-radio.biz/pipermail/flexradio_flex-radio.biz/ FlexRadio Homepage: http://www.flex-radio.com
Re: [Flexradio] Fw: 16 versus 24 bit audio
At 02:31 PM 5/19/2006, Peter Martinez wrote: From G3PLX: That's a picture of the broadband noise EMITTED from the audio OUTPUT side of the soundcard in question. My query is about the digital noise registered by the input ADC. The tests I have done so far say that there is 8 bits of background noise (1 bit = 6dB) coming from the 24-bit ADC in the Firebox with the input shorted. That says there's only 16-bits of useful signal in there. Why should I pay for 24 bits when 8 of them are below the noise? I say again: Is there anybody out there writing their own SDR software that has actually masked-off the bottom 8 bits or replaced it with random numbers? I've done a fair amount of A/D testing for a variety of RF applications, and have a few comments: 1) Have you tried making the noise measurement with a very clean sinewave input at various levels? (this is somewhat non trivial to generate) 2) Is the random low order noise white? Or does it have some spectral shaping? 3) It's possible that the limit of performance is set by something other than preamp noise before the A/D. For instance, if the clock jitter is only good to 16 bits, then there's not much point having a 24 bit noise level in the analog side. 4) It might be that 24 bit cards may not give you 24 bit performance, but might give you 18 bit or 20 bit performance, so you're better off than a 16 bit card giving you 14 bit performance 5) The other thing you get with things like the Firebox is multiple ins and outs. Jim ___ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archive Link: http://mail.flex-radio.biz/pipermail/flexradio_flex-radio.biz/ FlexRadio Homepage: http://www.flex-radio.com
Re: [Flexradio] 16 versus 24 bit audio
At 02:07 AM 5/20/2006, Peter Martinez wrote: From G3PLX: I just did some proper measurements on the Firebox. On runs of 1200 samples at 48kHz, the r.m.s. noise level on the line input is about 400. It's about 450 on the Mike input. I did this by squaring each sample, summing these, dividing by 1200, and taking the square root. At the same time I calculated the DC level, just to make sure that was a lot smaller and didn't confuse things. This is about 9 bits of noise, or more if you suppose the peaks are higher. On the built-in 16-bit card in this laptop the DC level is 15 and I am not sure how to allow for this in the r.m.s calculation, but only the lsb toggles randomly. The MP3+ is the same, unless I select the mike input when the rms noise level is about 10. These figures are what I would have expected intuitively. One would expect the analogue noise-level to be roughly the same as the quantisation noise, in the same way that one would optimise any receiver so that all sources of noise contribute more-or-less the same in order to maximise the dynamic range. Calculate the average of all the samples, then subtract that from the samples, then square, sum, and root. Or, if you have a statistics package, calculate the standard deviation of the input samples. That will be the rms noise voltage. Of more interest is actually running a clean sine wave in, and then looking at the rms noise power as a function of the digitized value. Analog input noise shows up as noise that is independent of where in the cycle it's sampled. Clock jitter shows up as increased noise near the zero crossings (where the derivative of the input is highest). James Lux, P.E. Spacecraft Radio Frequency Subsystems Group Flight Communications Systems Section Jet Propulsion Laboratory, Mail Stop 161-213 4800 Oak Grove Drive Pasadena CA 91109 tel: (818)354-2075 fax: (818)393-6875 ___ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archive Link: http://mail.flex-radio.biz/pipermail/flexradio_flex-radio.biz/ FlexRadio Homepage: http://www.flex-radio.com
Re: [Flexradio] Dayton
Cecil, so I can play with it while on vacation. OXYMORON OXYMORON OXYMORON SDR \= vacation You will spend ALL your time messing with the weird, wild, wonderous wonderful world of SDR-1000 and have no time for vacation. Welcome to the crowd. 73, Larry K2LT ___ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archive Link: http://mail.flex-radio.biz/pipermail/flexradio_flex-radio.biz/ FlexRadio Homepage: http://www.flex-radio.com
Re: [Flexradio] 16 versus 24 bit audio
At 04:35 AM 5/20/2006, Peter Martinez wrote: from G3PLX: Hello Sami. Thanks for joining the discussion - I feared I was on my own for a while! I hope some others will contribute too, so I don't get accused of hogging the bandwidth (or perhaps generating too much noise!). You said: If your low 8 bits are truly random with no input, that's a good thing! It follows that when you inject a non-random signal, it will stand out clearly from white noise. Let me be simple-minded and respond:- But if my low 8 bits are truly random and I inject an 8-bit sinewave, isn't it then level with the noise? If I could reduce my 8 bits of added noise to, say, 4 bits, wouldn't my sinewave then be 24dB above the noise? I don't see how adding that much noise can ever be a good thing to do. I am not trying to trap you, I really would like to understand what's going on here. This is all new stuff to me. I had a private email from a broadcast engineer who confirmed what I was saying about dither noise. He said they added 0.5 bits-worth of white noise to the analogue signal before digitisation, and subjectively that was the best result. But that's half a bit of dither, not 8 bits. One might add a few more bits of noise if one wasn't very sure of one's A/D linearity performance, and if it didn't impair the overall performance. If you're oversampling, for instance, and going to reduce a 96 ksps down to, say, 24 ksps, the power from the added noise would be reduced by the averaging you're doing with the sample rate reduction. Considering that most people will be filtering the output of the A/D to, say, 20Hz-20Khz, this might not be a bad design tradeoff. ___ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archive Link: http://mail.flex-radio.biz/pipermail/flexradio_flex-radio.biz/ FlexRadio Homepage: http://www.flex-radio.com
Re: [Flexradio] 16 versus 24 bit audio
From G3PLX: Sami is right. You CAN recover a signal from noise by narrowing the bandwidth, so if my signal was level with the noise in 24kHz bandwidth, I could filter it to a narrower bandwidth (in software) and improve it's SNR. But that's true regardless of the number of bits in the raw data. So long as we have at least half an lsb of additive noise to dither away the quantisation problem, we can always gain SNR by reducing the downstream software bandwidth. Any more added noise at the front end than this only makes things - well - er - noisier. The noise power calculation I did earlier shows that there is ALREADY about the right amount of noise inherent in the physics to get the dither optimum for a 24-bit ADC at 0dBm. If there are cards with more noise than this, it's probably because the designer couldn't get it any lower for the price, not because he chose to add more noise for some subtle reason. To take Jim's points, I have only so far measured the rms noise with no input, and not yet looked to see if there are any clues in it's spectrum - these things would take a lot more time. Clock jitter wouldn't explain what I see (an output with no input) although it would certainly cause noise in the presence of a large pure tone. I haven't tried that yet either. Let me close this topic before Phil accuses me of cruelty to dead horses. Before I aquired a 24-bit card, I honestly believed that 24-bit cards would be 8 bits better than 16 bit cards. When I did get one recently, I was surprised to find this wasn't the case. Jim is right. 24 bit cards may only be slightly better than 16-bit cards. I have learned something this week. 73 Peter ___ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archive Link: http://mail.flex-radio.biz/pipermail/flexradio_flex-radio.biz/ FlexRadio Homepage: http://www.flex-radio.com
Re: [Flexradio] Dayton
Welcome Cecil, it's a great radio and an amazing group. It puts the fun back into ham radio. Mike - AA8K cbayona wrote: My plans were that shortly after Dayton I would purchase a SDR-1000, but since I could not purchase the signal generator, and they had SDR-1000's in stock, I went ahead and purchased one. This was late yesterday as Dayton was closing so I dind't have a chance to purchase a small power supply and cables so I can play with it while on vacation. That will be taken care of shortly when I head for the bone yard. The weather yesterday was cloudy in the morning and sunny after 10:00AM, today is sunny also but it might rain in the afternoon. See ya in the funny papers. ___ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archive Link: http://mail.flex-radio.biz/pipermail/flexradio_flex-radio.biz/ FlexRadio Homepage: http://www.flex-radio.com
Re: [Flexradio] 16 versus 24 bit audio
On 5/20/06, Peter Martinez [EMAIL PROTECTED] wrote: From G3PLX: Let me close this topic before Phil accuses me of cruelty to dead horses. Before I aquired a 24-bit card, I honestly believed that 24-bit cards would be 8 bits better than 16 bit cards. When I did get one recently, I was surprised to find this wasn't the case. Jim is right. 24 bit cards may only be slightly better than 16-bit cards. I have learned something this week. 73 Peter Hi Peter, Well, I may have been a little too strong in making that statement (dead horse)...it was early morning here...no coffee yet consumed... etc... ;-) The FlexRadio Forum has some interesting discussions in the past about different sound cards and what to expect. It is pretty much true that some 24 bit cards are marginally better than some 16 bit cards. It also would be accurate to say that some 24 bit cards are worse than some of the better 16 bit cards. 73 de Phil N8VB ___ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archive Link: http://mail.flex-radio.biz/pipermail/flexradio_flex-radio.biz/ FlexRadio Homepage: http://www.flex-radio.com
Re: [Flexradio] 16 versus 24 bit audio
Thanks to everybody for the most interesting and educating discussion. Nevertheless, I am not happy until the JANUS version with AK5394A is in my hands and I have modified the QSD and the following amplifier. Best regards and special thanks to the HPSDR group for the good work done so far, Ahti OH2RZ On 20/05/06, Philip Covington [EMAIL PROTECTED] wrote: On 5/20/06, Peter Martinez [EMAIL PROTECTED] wrote: From G3PLX: Let me close this topic before Phil accuses me of cruelty to dead horses. Before I aquired a 24-bit card, I honestly believed that 24-bit cards would be 8 bits better than 16 bit cards. When I did get one recently, I was surprised to find this wasn't the case. Jim is right. 24 bit cards may only be slightly better than 16-bit cards. I have learned something this week. 73 Peter Hi Peter, Well, I may have been a little too strong in making that statement (dead horse)...it was early morning here...no coffee yet consumed... etc... ;-) The FlexRadio Forum has some interesting discussions in the past about different sound cards and what to expect. It is pretty much true that some 24 bit cards are marginally better than some 16 bit cards. It also would be accurate to say that some 24 bit cards are worse than some of the better 16 bit cards. 73 de Phil N8VB ___ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archive Link: http://mail.flex-radio.biz/pipermail/flexradio_flex-radio.biz/ FlexRadio Homepage: http://www.flex-radio.com ___ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archive Link: http://mail.flex-radio.biz/pipermail/flexradio_flex-radio.biz/ FlexRadio Homepage: http://www.flex-radio.com
Re: [Flexradio] 16 versus 24 bit audio
Message: 39 Date: Sat, 20 May 2006 16:09:52 - From: Peter Martinez [EMAIL PROTECTED] Subject: Re: [Flexradio] 16 versus 24 bit audio To: Flex Reflector FlexRadio@flex-radio.biz Message-ID: [EMAIL PROTECTED] Content-Type: text/plain; format=flowed; charset=iso-8859-1; reply-type=response From G3PLX: Sami is right. You CAN recover a signal from noise by narrowing the bandwidth, so if my signal was level with the noise in 24kHz bandwidth, I could filter it to a narrower bandwidth (in software) and improve it's SNR. I've been wondering about this lately; Isn't this getting close to what the definition of process gain is? Incidentally, Analog Devices has some excellent white papers that go into the details of the tradeoffs between sensitivity, dynamic range, resolution, etc. Definitely recommended reading. But that's true regardless of the number of bits in the raw data. So long as we have at least half an lsb of additive noise to dither away the quantisation problem, we can always gain SNR by reducing the downstream software bandwidth. Any more added noise at the front end than this only makes things - well - er - noisier. The noise power calculation I did earlier shows that there is ALREADY about the right amount of noise inherent in the physics to get the dither optimum for a 24-bit ADC at 0dBm. If there are cards with more noise than this, it's probably because the designer couldn't get it any lower for the price, not because he chose to add more noise for some subtle reason. To take Jim's points, I have only so far measured the rms noise with no input, and not yet looked to see if there are any clues in it's spectrum - these things would take a lot more time. Clock jitter wouldn't explain what I see (an output with no input) although it would certainly cause noise in the presence of a large pure tone. I haven't tried that yet either. It would be interesting to see the spectral characteristics of the noise. Let me close this topic before Phil accuses me of cruelty to dead horses. Before I aquired a 24-bit card, I honestly believed that 24-bit cards would be 8 bits better than 16 bit cards. When I did get one recently, I was surprised to find this wasn't the case. Jim is right. 24 bit cards may only be slightly better than 16-bit cards. I have learned something this week. Seems to me that the marketing folks take the number of bits in the ADC and run with it. A 16 bit card is only 14 bits, and a 24 bit card is only 18 bits, so the 24 bit card is 4 bits better than the 16 bit card. Cheers, -- Larry Gadallah, VE6VQ/W7 lgadallah AT gmail DOT com -- next part -- An HTML attachment was scrubbed... URL: http://mail.flex-radio.biz/pipermail/flexradio_flex-radio.biz/attachments/20060520/eadbfa34/attachment.html ___ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archive Link: http://mail.flex-radio.biz/pipermail/flexradio_flex-radio.biz/ FlexRadio Homepage: http://www.flex-radio.com
[Flexradio] The Flex Suite @ Dayton is now on TeamSpeak
Eric was able to get free wireless for the TeamSpeak connection. How resourceful! -Tim --- Tim Ellison mailto:[EMAIL PROTECTED] Integrated Technical Services http://www.itsco.com/ Apex, NC USA 919.674.0044 Ext. 25 / 919.674.0045 (FAX) 919.215.6375 - cell PGP public key available at all public KeyServers Skype: kg4rzy ___ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archive Link: http://mail.flex-radio.biz/pipermail/flexradio_flex-radio.biz/ FlexRadio Homepage: http://www.flex-radio.com
[Flexradio] vCOM Dowwnload Not Working
Phil Covington - I notice that the vCOM Download button on your web site is inoperative. John Denson ___ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archive Link: http://mail.flex-radio.biz/pipermail/flexradio_flex-radio.biz/ FlexRadio Homepage: http://www.flex-radio.com -- No virus found in this incoming message. Checked by AVG Free Edition. Version: 7.1.392 / Virus Database: 268.6.1/344 - Release Date: 5/19/2006 ___ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archive Link: http://mail.flex-radio.biz/pipermail/flexradio_flex-radio.biz/ FlexRadio Homepage: http://www.flex-radio.com
Re: [Flexradio] vCOM Dowwnload Not Working
On 5/20/06, John Denson [EMAIL PROTECTED] wrote: Phil Covington - I notice that the vCOM Download button on your web site is inoperative. John Denson It works and I haven't changed anything for months. You might want to try again. Phil C ___ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archive Link: http://mail.flex-radio.biz/pipermail/flexradio_flex-radio.biz/ FlexRadio Homepage: http://www.flex-radio.com
