RE: [Elecraft] K3 related - non-linear audio transformer behavior
On Sun, 21 Sep 2008 20:42:27 -0400, Joe Subich, W4TV wrote: >I think is it safe to treat the audio as band limited That's like saying a driver is slow. How slow? Bandwidth limiting CHANGES the complex impulse response of the system. It does not make it not matter, or benign, just DIFFERENT. And the bandlimiting is quite variable, thanks to the design and implementation of K3 operating controls of the DSP. Also, note that the impulse response is complex -- that is, if we looked at it as a frequency response it would have a phase response too. One of the important and complex problems that Lyle has to solve (and he's solved it pretty well if he doesn't hit the transformers, according to my ears) is a nice phase (time) response. Jim K9YC ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
RE: [Elecraft] K3 related - non-linear audio transformer behavior
Paul, Looking at the Line Out with noise from an Elecraft N-Gen indicates the K3 audio is quite dramatically band limited. With the maximum DSP high cut frequency and the 13 KHz first IF filter, broadband detected noise in either AM or SSB drops 45 dB between 4 KHz and 4.2 KHz with a further 15 dB roll off between 4.2 KHz and 9 KHz where it reaches the noise floor of the measuring device. The HF limit for data modes is also 4 KHz - depending on data sub-mode and center frequency. The HF limit for CW is approximately 2.5 KHz with the highest available "Spot" frequency and center frequency (shift). I think is it safe to treat the audio as band limited ... 73, ... Joe, W4TV > -Original Message- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of Paul > Christensen > Sent: Sunday, September 21, 2008 4:51 PM > To: Jack Smith; Jim Brown > Cc: Elecraft List > Subject: Re: [Elecraft] K3 related - non-linear audio > transformer behavior > > > > That's why I question the applicability of a ringing test with a > > square > > wave having a rise/fall time measured in nanoseconds, as > the audio that > > makes it through the K3's crystal and DSP will not remotely > resemble that > > waveform. > > Agreed Jack, if the DSP and/or AF stages truly limit impulses > through the > transformer. To Jim's point, ignore the modulation type for > the moment and > consider an impulse noise such as that created by the start > of light switch > or AC motor. If the system received BW is wide enough (e.g., > selecting the > K3's 6 kHz, or especially the 12 kHz filter), I suspect that > transient > impulse response becomes meaningful. I have not yet tried to > sweep the K3's > audio section beyond 4 kHz and the DSP and/or audio sections > may preclude an > audio response beyond that point. > > One way of testing this is to turn on/off various types of real noise > sources as a function of selected filter BW and while > observing a scope on > the output of the line-out transformer, record the > differences in peak > values with and without terminating resistance on the transformer > secondary -- taking into account any level difference created by the > addition of the terminating resistor. > > Paul, W9AC > ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] K3 related - non-linear audio transformer behavior
That's why I question the applicability of a ringing test with a square wave having a rise/fall time measured in nanoseconds, as the audio that makes it through the K3's crystal and DSP will not remotely resemble that waveform. Agreed Jack, if the DSP and/or AF stages truly limit impulses through the transformer. To Jim's point, ignore the modulation type for the moment and consider an impulse noise such as that created by the start of light switch or AC motor. If the system received BW is wide enough (e.g., selecting the K3's 6 kHz, or especially the 12 kHz filter), I suspect that transient impulse response becomes meaningful. I have not yet tried to sweep the K3's audio section beyond 4 kHz and the DSP and/or audio sections may preclude an audio response beyond that point. One way of testing this is to turn on/off various types of real noise sources as a function of selected filter BW and while observing a scope on the output of the line-out transformer, record the differences in peak values with and without terminating resistance on the transformer secondary -- taking into account any level difference created by the addition of the terminating resistor. Paul, W9AC ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] K3 related - non-linear audio transformer behavior
On Sun, 21 Sep 2008 13:31:00 -0400, Jack Smith wrote: >Have you considered the difference between hitting a transformer with a >fast rise / fast fall square wave and hitting it with one that is >narrowly band limited? That's one of the virtues of my measurement method -- it looks at the response of the transformer with band-limited noise as the signal source, and the band-limiting is the filters in the K3. Jim ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] K3 related - non-linear audio transformer behavior
Have you considered the difference between hitting a transformer with a fast rise / fast fall square wave and hitting it with one that is narrowly band limited? Ignoring for the moment the difference in filter shape between Gaussian and the complex shape of the K3 crystal and DSP filters, the rise/fall time of a perfect square wave fed into a Gaussian filter is 0.34/BW, or for a 1 KHz bandwidth, 340 microseconds. I have not yet measured but hope to later today, the transformers with a slow rise/fall waveform. A rather different story can be found, I suspect, in other audio applications where the source bandwidth may easily be 20 KHz or greater, yielding a rise/fall of 17 us or less. The slowest ringing rate I found was around 125 KHz, or 8 us for a period. I can see how that might be excited by a 17 us rise/fall square wave. I just don't see the same effect occurring with 340 us rise/fall "square wave." I use quotes around "square wave" because that leads to the image of a waveform with an abrupt rise/fall which is not the case where the bandwidth is limited to a few hundred Hz or a KHz at most. That's why I question the applicability of a ringing test with a square wave having a rise/fall time measured in nanoseconds, as the audio that makes it through the K3's crystal and DSP will not remotely resemble that waveform. Jack K8ZOA Jim Brown wrote: On Sun, 21 Sep 2008 09:11:22 -0400, Paul Christensen wrote: the square-wave impulse response of the transformer becomes less meaningful. As long as there is impulse noise, the square wave response of the line out transformer is definitely relevant! As the folks at Elecraft have noted, the primary function of the Line Out is to drive data decoders of one sort or another. Those decoders see signal plus noise. Any distortion in the transformer is additional noise as far as the decoder is concerned. The square wave response of the circuit is simply another way of LOOKING at those distortion products. The analysis of the K3 Line Out that I did back in June using band noise as a source of excitation show the same problems as Jack's analysis using very different signal sources, but my excitation, being broadband, exposes the IM distortion as apparent broadening of the filter skirts. Jack measures IM using traditional two-tone methods. In other words, we both see the same problems using very different methods to study them. Those of us working in pro audio learned long ago that broadband noise (we use pink noise) is a VERY powerful analysis tool. 73, Jim Brown K9YC Audio Systems Group, Inc. ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] K3 related - non-linear audio transformer behavior
On Sun, 21 Sep 2008 09:11:22 -0400, Paul Christensen wrote: >the square-wave impulse response >of the transformer becomes less meaningful. As long as there is impulse noise, the square wave response of the line out transformer is definitely relevant! As the folks at Elecraft have noted, the primary function of the Line Out is to drive data decoders of one sort or another. Those decoders see signal plus noise. Any distortion in the transformer is additional noise as far as the decoder is concerned. The square wave response of the circuit is simply another way of LOOKING at those distortion products. The analysis of the K3 Line Out that I did back in June using band noise as a source of excitation show the same problems as Jack's analysis using very different signal sources, but my excitation, being broadband, exposes the IM distortion as apparent broadening of the filter skirts. Jack measures IM using traditional two-tone methods. In other words, we both see the same problems using very different methods to study them. Those of us working in pro audio learned long ago that broadband noise (we use pink noise) is a VERY powerful analysis tool. 73, Jim Brown K9YC Audio Systems Group, Inc. ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] K3 related - non-linear audio transformer behavior
The usefulness of the square-wave response plots (as you and I have conducted) relies primarily on the complexity of the received waveform and system bandwidth. Even in the case of a CW square-wave-like signal, a gently sloping rise/decay time (e.g., raised-cosine CW waveform), greatly reduces occupied transmitted bandwidth and the square-wave impulse response of the transformer becomes less meaningful. OTOH, if there was to exist some form of data mode in which short rise/fall times are required, then a wider, flatter, overall receive bandwidth is required. Presently, I know of no such common data modes for amateur use, but this may apply to some commercial and/or military data modulation methods. Regardless of whether this is an issue or non-issue for amateur use, I have demonstrated (on the Elecraft mail list through Yahoo) that the problem is cleanly solved in even the cheapest datacom transformers through a simple termination of the secondary winding. The peace of mind of knowing that a sound card will not be over-driven by a brief spike in transformer overshoot is certainly worth cost of a single resistor between the transformer and sound card input. Paul, W9AC - Original Message - From: "Jack Smith" <[EMAIL PROTECTED]> To: "Paul Christensen" <[EMAIL PROTECTED]> Cc: "'Elecraft'" Sent: Saturday, September 20, 2008 6:42 PM Subject: Re: [Elecraft] K3 related - non-linear audio transformer behavior Paul: I've revised my non-linear transformer page in two respects: 1. Added the plot you requested. (Almost at the bottom of the page) 2. Added square wave ringing data for four transformers, although I am not at all convinced that square wave ringing is an appropriate figure of merit for a transformer used in a narrowly bandwidth limited communications receiver. The page is: http://www.cliftonlaboratories.com/non-linear_transformer_behavior.htm Paul Christensen wrote: Jack: With regard to the plots under "Comparisons and Conclusions," and also under "Frequency Response Compared," is it possible to change the source Z from 600-ohms to 50-ohms and re-test? It would be an interesting exercise to see if THD (at ~ 1V RMS) and the high-end frequency response of the Bourns transformer changes significantly. Tnx! Paul, W9AC - Original Message - From: "Jack Smith" <[EMAIL PROTECTED]> To: "'Elecraft'" Sent: Saturday, September 20, 2008 8:02 AM Subject: [Elecraft] K3 related - non-linear audio transformer behavior I've spent the last two weeks measuring and analyzing non-linear behavior of several audio transformers, focusing on the Tamura TTC-108 used as isolation transformers in the K3. My data and analysis is now available at http://www.cliftonlaboratories.com/non-linear_transformer_behavior.htm Jack K8ZOA www.cliftonlaboratories.com ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] K3 related - non-linear audio transformer behavior
Indeed, similar harmonic and IMD distortion are created inside the LINE IN transformer. The question is their level and importance. The LINE IN transformer, however, is fed by a 10:1 voltage divider, 604R in series with 62R shunted across the transformer primary. This arrangement provides a lower drive impedance to the transformer, around 56 ohms as a matter of fact. (Assumes the LINE IN port is driven by a low impedance source, which I believe is the case for the typical sound card output.) 56 Ohms is low enough to see significant THD improvement over a straight 604 ohm series resistor according to my measurements. It should be possible to measure harmonics generated by the input transformer, perhaps using the monitor function. I'm too far behind on other projects to work on it at the moment, however. Jack Paul Fletcher wrote: Jack, Thanks for the research - very interesting and it looks like a simple fix to improve the performance of the K3 significantly. You've got me wondering now though about DATA-A modes. As the K3 uses the same transformer for line in your work suggests that the transmit performance will be affected by the sound card output impedance - worth considering at least. Cheers, Paul M1PAF ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] K3 related - non-linear audio transformer behavior
Jack, Thanks for the research - very interesting and it looks like a simple fix to improve the performance of the K3 significantly. You've got me wondering now though about DATA-A modes. As the K3 uses the same transformer for line in your work suggests that the transmit performance will be affected by the sound card output impedance - worth considering at least. Cheers, Paul M1PAF -- View this message in context: http://n2.nabble.com/K3-related---non-linear-audio-transformer-behavior-tp1106188p1107335.html Sent from the Elecraft mailing list archive at Nabble.com. ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] K3 related - non-linear audio transformer behavior
Paul: I've revised my non-linear transformer page in two respects: 1. Added the plot you requested. (Almost at the bottom of the page) 2. Added square wave ringing data for four transformers, although I am not at all convinced that square wave ringing is an appropriate figure of merit for a transformer used in a narrowly bandwidth limited communications receiver. The page is: http://www.cliftonlaboratories.com/non-linear_transformer_behavior.htm Paul Christensen wrote: Jack: With regard to the plots under "Comparisons and Conclusions," and also under "Frequency Response Compared," is it possible to change the source Z from 600-ohms to 50-ohms and re-test? It would be an interesting exercise to see if THD (at ~ 1V RMS) and the high-end frequency response of the Bourns transformer changes significantly. Tnx! Paul, W9AC - Original Message - From: "Jack Smith" <[EMAIL PROTECTED]> To: "'Elecraft'" Sent: Saturday, September 20, 2008 8:02 AM Subject: [Elecraft] K3 related - non-linear audio transformer behavior I've spent the last two weeks measuring and analyzing non-linear behavior of several audio transformers, focusing on the Tamura TTC-108 used as isolation transformers in the K3. My data and analysis is now available at http://www.cliftonlaboratories.com/non-linear_transformer_behavior.htm Jack K8ZOA www.cliftonlaboratories.com ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] K3 related - non-linear audio transformer behavior
Jack: With regard to the plots under "Comparisons and Conclusions," and also under "Frequency Response Compared," is it possible to change the source Z from 600-ohms to 50-ohms and re-test? It would be an interesting exercise to see if THD (at ~ 1V RMS) and the high-end frequency response of the Bourns transformer changes significantly. Tnx! Paul, W9AC - Original Message - From: "Jack Smith" <[EMAIL PROTECTED]> To: "'Elecraft'" Sent: Saturday, September 20, 2008 8:02 AM Subject: [Elecraft] K3 related - non-linear audio transformer behavior I've spent the last two weeks measuring and analyzing non-linear behavior of several audio transformers, focusing on the Tamura TTC-108 used as isolation transformers in the K3. My data and analysis is now available at http://www.cliftonlaboratories.com/non-linear_transformer_behavior.htm Jack K8ZOA www.cliftonlaboratories.com ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
