Re: [Elecraft] IMD and CW
On Fri,12/23/2016 10:11 AM, Alan Bloom wrote: You could always compensate for it by adjusting the K3 for softer key shaping. Wayne carefully shaped the keying waveform to minimize occupied bandwidth while maintaining good clarity at high keying speeds, and he purposely did not allow users to screw it up. :) 73, Jim K9YC __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] IMD and CW
Yes was thinking it was something new. Thank´s Alan 73 merry xmas / Jim SM2EKM On 2016-12-24 06:23, Alan Bloom wrote: Apparently you can't. I must have been thinking of the weight adjustment. Alan N1AL On 12/23/2016 09:22 PM, Jan Erik Holm wrote: On 2016-12-23 19:11, Alan Bloom wrote: You could always compensate for it by adjusting the K3 for softer key shaping. Alan N1AL How do you do that ? / 73 Jim __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] IMD and CW
Apparently you can't. I must have been thinking of the weight adjustment. Alan N1AL On 12/23/2016 09:22 PM, Jan Erik Holm wrote: On 2016-12-23 19:11, Alan Bloom wrote: You could always compensate for it by adjusting the K3 for softer key shaping. Alan N1AL How do you do that ? / 73 Jim __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] IMD and CW
On 2016-12-23 19:11, Alan Bloom wrote: You could always compensate for it by adjusting the K3 for softer key shaping. Alan N1AL How do you do that ? / 73 Jim __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] IMD and CW
Not in my experience as a broadcast engineer in the 1950's. Class C amplifiers, plate modulated, were the standard low distortion transmitters for decades, just as they were used in the best A.M. Ham rigs like the Johnson Kilowatt. But, as the big commercial stations came on the air running 50 kw the scramble was on to find an alternative to having an audio amplifier that could produce a full 25 kw of clean audio to modulate them, requiring a modulation transformer the size of one of the huge transformers at the local power mains distribution center. That is when, IMX, all sorts of alternative schemes for modulation, all of which were less "clean" (although still very good when handled correctly) came into use. Stations chose more complex and careful adjustment during operation than investment in hardware and facilities. But, after all, in the US the station had to have a broadcast engineer monitoring the transmitter at all times, logging critical readings every half hour. 73 Ron AC7AC -Original Message- From: Elecraft [mailto:elecraft-boun...@mailman.qth.net] On Behalf Of Fred Jensen Sent: Friday, December 23, 2016 4:38 PM To: elecraft@mailman.qth.net Subject: Re: [Elecraft] IMD and CW This has drifted fairly far from the original. Thus encouraged ... I wondered about that and being retired I pursued it, ultimately with the tech folks [well, one folk] at WWV who repeatedly assured me that they were on-frequency and that their time information was correct which of course was never the issue. Somewhere in all the words I read about the station, I did find a reference to plate modulated Class-C transmitters but I have lost it's QTH on this disk drive. Most plate modulators ran Class-B or -AB, and were subject to cross-over non-linearities. The 5, 10, and 15 MHz signals look very much the same on the spectrum display which [weakly] suggests the unexpected distortion products may arise somewhere in the baseband chain. The 2.5 and 20 MHz transmitters, being low-level modulated, may tap that chain before the distortion is introduced. ARC-5's, when cathode-keyed, were notorious for key clicks, almost as bad as the Yeasu rigs of recent eras. [:-) Of course, for my K3, the "carrier-balance" and "opposite sideband suppression" is perfect. I think, but don't know, that the K3 shapes the CW with a raised-cosine filter. With strong signals, it *is* possible to identify a K3 by its CW spectrum, particularly in the WF. Fred K6DGW Sparks NV DM09dn Washoe County __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] IMD and CW
This has drifted fairly far from the original. Thus encouraged ... I wondered about that and being retired I pursued it, ultimately with the tech folks [well, one folk] at WWV who repeatedly assured me that they were on-frequency and that their time information was correct which of course was never the issue. Somewhere in all the words I read about the station, I did find a reference to plate modulated Class-C transmitters but I have lost it's QTH on this disk drive. Most plate modulators ran Class-B or -AB, and were subject to cross-over non-linearities. The 5, 10, and 15 MHz signals look very much the same on the spectrum display which [weakly] suggests the unexpected distortion products may arise somewhere in the baseband chain. The 2.5 and 20 MHz transmitters, being low-level modulated, may tap that chain before the distortion is introduced. ARC-5's, when cathode-keyed, were notorious for key clicks, almost as bad as the Yeasu rigs of recent eras. [:-) Of course, for my K3, the "carrier-balance" and "opposite sideband suppression" is perfect. I think, but don't know, that the K3 shapes the CW with a raised-cosine filter. With strong signals, it *is* possible to identify a K3 by its CW spectrum, particularly in the WF. Fred K6DGW Sparks NV DM09dn Washoe County --Northern California Contest Club --CU in the Cal QSO Party --7-8 Oct 2017 On 12/23/2016 3:46 PM, Ron D'Eau Claire wrote: The fact that the RF amplifier is running Class C should not be an issue if it is plate-modulated. Plate modulation is the "gold standard" because only the RF carrier is being amplified in the Class C stage. Beyond that its non-linearity is employed to mix the modulating signals with the RF carrier. While the process is extremely linear, it takes a lot of audio level power - at least 1/2 of the RF carrier power. Fred's observation makes me think WWV may be using some sort of "compromise" system such as grid modulation rather than plate modulation. Much lower audio (baseband) power required, but it is not as linear either. 73, Ron AC7AC __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] IMD and CW
I believe the K3/K3S use a raised sinusoid key shaping. It is a good compromise to reduce the bandwidth without excessive ringing/backwave. In the bad old days, CW key shaping was typically a simple R-C filter on the key line. That resulted in an exponential rise and fall, which resulted in more key clicks for a given rise/fall time than a raised sinusoid. Alan N1AL On 12/23/2016 01:30 PM, K9MA wrote: On 12/23/2016 12:11, Alan Bloom wrote: For a CW signal, the nonlinearity of a typical power amplifier should have the effect of shortening the rise and fall times. That does indeed widen the transmitted bandwidth. But intuitively, it seems like the distortion would have to be really bad to shorten the rise/fall times by much. You could always compensate for it by adjusting the K3 for softer key shaping. Alan N1AL I think it's a little more complicated than that: The K3 shapes the CW waveform very carefully, to minimize bandwidth. (I think it's equivalent to passing the signal through a narrow bandpass filter.) Obviously, any distortion downstream is going to compromise that careful shaping. However, based on my intuition and Vic's results, I suspect it would take a truly terrible amount of distortion to significantly increase the CW bandwidth. Given that the K3 is so much cleaner than many other popular radios, I doubt we need to worry. 73, Scott K9MA __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] IMD and CW
The fact that the RF amplifier is running Class C should not be an issue if it is plate-modulated. Plate modulation is the "gold standard" because only the RF carrier is being amplified in the Class C stage. Beyond that its non-linearity is employed to mix the modulating signals with the RF carrier. While the process is extremely linear, it takes a lot of audio level power - at least 1/2 of the RF carrier power. Fred's observation makes me think WWV may be using some sort of "compromise" system such as grid modulation rather than plate modulation. Much lower audio (baseband) power required, but it is not as linear either. 73, Ron AC7AC -Original Message- From: Elecraft [mailto:elecraft-boun...@mailman.qth.net] On Behalf Of K9MA Sent: Friday, December 23, 2016 2:39 PM To: elecraft@mailman.qth.net Subject: Re: [Elecraft] IMD and CW Very interesting, Fred. It makes sense, though, that plate modulated class-C amplifiers aren't terribly linear. On the other hand, that kind of distortion probably doesn't affect WWV's mission. I wonder if the AM broadcast industry achieves lower distortion. Feedback comes to mind. 73, Scott K9MA On 12/23/2016 15:53, Fred Jensen wrote: > Not CW, and this probably won't work in 4X-land, but if you want to > see the difference a Class-C amp makes, set your P3 span to about 6 > KHz, and tune in WWV on its various frequencies. During the tone-on > minutes, the 2.5 and 20 MHz signals will look as you expect an AM > signal with a tone modulating it ... two sidebands on either side of > the carrier. If you look very close, you can see the 100 Hz > sub-carrier, and if you narrow things down enough, you can see the > sidebands generated around it by the IRIG-H time code. These two > transmitters are low level modulated with linear amplification. > > The 5, 10, and 15 MHz transmitters are plate-modulated Class-C and > look markedly different. The two sidebands are there, but so are > their 2nd and 3rd harmonics [sometimes when WWV is really strong, I > can make out the 4th harmonic]. The 100 Hz sub-carrier and the IRIG-H > sidebands are there as you would expect, but they also surround the > audio sidebands and harmonics. > > WWV builds one baseband with all the tones, ticks, burps, codes, and > voice and it modulates all 5 transmitters. The difference between the > TX is really striking and a bit disappointing. I've always assumed > WWV was the "gold-standard." > > Fred K6DGW > Sparks NV DM09dn > Washoe County > > --Northern California Contest Club > --CU in the Cal QSO Party > --7-8 Oct 2017 > > On 12/22/2016 10:22 PM, Vic Rosenthal wrote: >> I didn't exactly do this, but I did investigate the effects of >> distortion on CW signals. I disconnected my P3 from the K3 and set >> the IF to 7 MHz. so it would act like a standalone spectrum analyzer. >> I was interested in whether a class-C amplifier I had built would >> sharpen the keying enough to create noticeable clicks. The amplifier >> used minimal fixed bias to allow a small amount of resting plate >> current in transmit mode, with full class-C operating bias provided >> by a grid resistor. >> I noted a broadening of the base of the signal on the P3, indicating >> that the signal was not as clean as the K3 alone. But listening with >> another receiver on either side of the S9+30 dB signal didn't reveal >> audible clicks. I also asked other operators to listen and there were >> no reports of clicks. >> I am sure that attempting to use that amplifier (a pair of 813s) on >> SSB would have gotten me ridden out of town on a rail! >> >> Vic 4X6GP >> > > __ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:Elecraft@mailman.qth.net > > This list hosted by: http://www.qsl.net Please help support this email > list: http://www.qsl.net/donate.html Message delivered to > k...@sdellington.us -- Scott K9MA k...@sdellington.us __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to r...@elecraft.com __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] IMD and CW
Google "ampliphase" ... OKA: "The Transmitter all broadcast engineers hate." All linear phase modulation until AM magically squirts out the top. Factoid: When WWV was brand new, it transmitted farm reports for the Agriculture Department ... using Morse code. I'm guessing the number of farmers fluent in Morse might have been two ... three tops. I remember WWV using Morse, but by then it was Eastern Standard Time, not farm reports. Fred K6DGW Sparks NV DM09dn Washoe County --Northern California Contest Club --CU in the Cal QSO Party --7-8 Oct 2017On 12/23/2016 2:39 PM, K9MA wrote: Very interesting, Fred. It makes sense, though, that plate modulated class-C amplifiers aren't terribly linear. On the other hand, that kind of distortion probably doesn't affect WWV's mission. I wonder if the AM broadcast industry achieves lower distortion. Feedback comes to mind. 73, Scott K9MA __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] IMD and CW
Very interesting, Fred. It makes sense, though, that plate modulated class-C amplifiers aren't terribly linear. On the other hand, that kind of distortion probably doesn't affect WWV's mission. I wonder if the AM broadcast industry achieves lower distortion. Feedback comes to mind. 73, Scott K9MA On 12/23/2016 15:53, Fred Jensen wrote: Not CW, and this probably won't work in 4X-land, but if you want to see the difference a Class-C amp makes, set your P3 span to about 6 KHz, and tune in WWV on its various frequencies. During the tone-on minutes, the 2.5 and 20 MHz signals will look as you expect an AM signal with a tone modulating it ... two sidebands on either side of the carrier. If you look very close, you can see the 100 Hz sub-carrier, and if you narrow things down enough, you can see the sidebands generated around it by the IRIG-H time code. These two transmitters are low level modulated with linear amplification. The 5, 10, and 15 MHz transmitters are plate-modulated Class-C and look markedly different. The two sidebands are there, but so are their 2nd and 3rd harmonics [sometimes when WWV is really strong, I can make out the 4th harmonic]. The 100 Hz sub-carrier and the IRIG-H sidebands are there as you would expect, but they also surround the audio sidebands and harmonics. WWV builds one baseband with all the tones, ticks, burps, codes, and voice and it modulates all 5 transmitters. The difference between the TX is really striking and a bit disappointing. I've always assumed WWV was the "gold-standard." Fred K6DGW Sparks NV DM09dn Washoe County --Northern California Contest Club --CU in the Cal QSO Party --7-8 Oct 2017 On 12/22/2016 10:22 PM, Vic Rosenthal wrote: I didn't exactly do this, but I did investigate the effects of distortion on CW signals. I disconnected my P3 from the K3 and set the IF to 7 MHz. so it would act like a standalone spectrum analyzer. I was interested in whether a class-C amplifier I had built would sharpen the keying enough to create noticeable clicks. The amplifier used minimal fixed bias to allow a small amount of resting plate current in transmit mode, with full class-C operating bias provided by a grid resistor. I noted a broadening of the base of the signal on the P3, indicating that the signal was not as clean as the K3 alone. But listening with another receiver on either side of the S9+30 dB signal didn't reveal audible clicks. I also asked other operators to listen and there were no reports of clicks. I am sure that attempting to use that amplifier (a pair of 813s) on SSB would have gotten me ridden out of town on a rail! Vic 4X6GP __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to k...@sdellington.us -- Scott K9MA k...@sdellington.us __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] IMD and CW
Not CW, and this probably won't work in 4X-land, but if you want to see the difference a Class-C amp makes, set your P3 span to about 6 KHz, and tune in WWV on its various frequencies. During the tone-on minutes, the 2.5 and 20 MHz signals will look as you expect an AM signal with a tone modulating it ... two sidebands on either side of the carrier. If you look very close, you can see the 100 Hz sub-carrier, and if you narrow things down enough, you can see the sidebands generated around it by the IRIG-H time code. These two transmitters are low level modulated with linear amplification. The 5, 10, and 15 MHz transmitters are plate-modulated Class-C and look markedly different. The two sidebands are there, but so are their 2nd and 3rd harmonics [sometimes when WWV is really strong, I can make out the 4th harmonic]. The 100 Hz sub-carrier and the IRIG-H sidebands are there as you would expect, but they also surround the audio sidebands and harmonics. WWV builds one baseband with all the tones, ticks, burps, codes, and voice and it modulates all 5 transmitters. The difference between the TX is really striking and a bit disappointing. I've always assumed WWV was the "gold-standard." Fred K6DGW Sparks NV DM09dn Washoe County --Northern California Contest Club --CU in the Cal QSO Party --7-8 Oct 2017 On 12/22/2016 10:22 PM, Vic Rosenthal wrote: I didn't exactly do this, but I did investigate the effects of distortion on CW signals. I disconnected my P3 from the K3 and set the IF to 7 MHz. so it would act like a standalone spectrum analyzer. I was interested in whether a class-C amplifier I had built would sharpen the keying enough to create noticeable clicks. The amplifier used minimal fixed bias to allow a small amount of resting plate current in transmit mode, with full class-C operating bias provided by a grid resistor. I noted a broadening of the base of the signal on the P3, indicating that the signal was not as clean as the K3 alone. But listening with another receiver on either side of the S9+30 dB signal didn't reveal audible clicks. I also asked other operators to listen and there were no reports of clicks. I am sure that attempting to use that amplifier (a pair of 813s) on SSB would have gotten me ridden out of town on a rail! Vic 4X6GP __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] IMD and CW
On 12/23/2016 12:11, Alan Bloom wrote: For a CW signal, the nonlinearity of a typical power amplifier should have the effect of shortening the rise and fall times. That does indeed widen the transmitted bandwidth. But intuitively, it seems like the distortion would have to be really bad to shorten the rise/fall times by much. You could always compensate for it by adjusting the K3 for softer key shaping. Alan N1AL I think it's a little more complicated than that: The K3 shapes the CW waveform very carefully, to minimize bandwidth. (I think it's equivalent to passing the signal through a narrow bandpass filter.) Obviously, any distortion downstream is going to compromise that careful shaping. However, based on my intuition and Vic's results, I suspect it would take a truly terrible amount of distortion to significantly increase the CW bandwidth. Given that the K3 is so much cleaner than many other popular radios, I doubt we need to worry. 73, Scott K9MA -- Scott K9MA k...@sdellington.us __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] IMD and CW
For a CW signal, the nonlinearity of a typical power amplifier should have the effect of shortening the rise and fall times. That does indeed widen the transmitted bandwidth. But intuitively, it seems like the distortion would have to be really bad to shorten the rise/fall times by much. You could always compensate for it by adjusting the K3 for softer key shaping. Alan N1AL On 12/22/2016 10:22 PM, Vic Rosenthal wrote: I didn't exactly do this, but I did investigate the effects of distortion on CW signals. I disconnected my P3 from the K3 and set the IF to 7 MHz. so it would act like a standalone spectrum analyzer. I was interested in whether a class-C amplifier I had built would sharpen the keying enough to create noticeable clicks. The amplifier used minimal fixed bias to allow a small amount of resting plate current in transmit mode, with full class-C operating bias provided by a grid resistor. I noted a broadening of the base of the signal on the P3, indicating that the signal was not as clean as the K3 alone. But listening with another receiver on either side of the S9+30 dB signal didn't reveal audible clicks. I also asked other operators to listen and there were no reports of clicks. I am sure that attempting to use that amplifier (a pair of 813s) on SSB would have gotten me ridden out of town on a rail! Vic 4X6GP On 22 Dec 2016, at 23:10, K9MA wrote: On 12/22/2016 11:40, Jim Brown wrote: IMD also affects CW. What we call CW is not "continuous wave," it is a continuous wave that is 100% modulated by a rectangular wave. That rectangular wave is rich in harmonics, and excites IMD. We hear it as clicks. It would be interesting to see how much IMD it takes to significantly increase key clicks of a "clean" keyed CW signal, like that of the K3. I'd expect the effect to be small, compared to that on an SSB signal for the same level of IMD, but I could be wrong. I suppose a simple test would be to have a local friend with a P3 watch the signal as I turned down the supply voltage on my K3. Has anyone tried anything like that? 73, Scott K9MA -- Scott K9MA k...@sdellington.us __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to k2vco@gmail.com __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to n...@sonic.net __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
