CW rise time mod
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Elecraft says.....
"Some owners prefer a faster CW keying waveform rise time. The rise time can be reduced from about 8 milliseconds to 5 milliseconds without affecting the fall time by replacing capacitor C222 on the K3 main RF board with a 0.1 uF capacitor. This change will also allow a future firmware revision to further reduce rise time via a menu entry." But the schematics of the RF Board Rev. A4 (Sheet 3 of 4), dated 9/19/07, show C222 as being 0.1 already. The instructions recommend removing the existing 0.1 and replacing it with another 0.1 !! Surely to reduce the rise time the existing capacitor should be shunted with another one. Or do Rev A RF boards have a lower value for C222 than that shown on the schematic? 73 -- David G4DMP Leeds, England, UK _______________________________________________ Elecraft mailing list Post to: [hidden email] 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 |
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Hi David:
I measured C222 *in place* with my aade cap checker and it measured ~1 uF(actually 0.965 uF)... not the 0.1 in the schematic. I'm guessing that the schematic available for download is not current with production. Someone else here mentioned that C222 was 1 uF, but I don't remember who it was. 73, Ken K3IU David Pratt wrote: > Elecraft says..... > "Some owners prefer a faster CW keying waveform rise time. The rise > time can be reduced from about 8 milliseconds to 5 milliseconds > without affecting the fall time by replacing capacitor C222 on the K3 > main RF board with a 0.1 uF capacitor. This change will also allow a > future firmware revision to further reduce rise time via a menu entry." > > But the schematics of the RF Board Rev. A4 (Sheet 3 of 4), dated > 9/19/07, show C222 as being 0.1 already. The instructions recommend > removing the existing 0.1 and replacing it with another 0.1 !! Surely > to reduce the rise time the existing capacitor should be shunted with > another one. > > Or do Rev A RF boards have a lower value for C222 than that shown on > the schematic? > > 73 Elecraft mailing list Post to: [hidden email] 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 |
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In a recent message, Ken Wagner <[hidden email]> writes
>I measured C222 *in place* with my aade cap checker and it measured ~1 >uF(actually 0.965 uF)... not the 0.1 in the schematic. I'm guessing >that the schematic available for download is not current with >production. Someone else here mentioned that C222 was 1 uF, but I >don't remember who it was. Thanks Ken, and Dave G4AON, it looks as though a batch of RF boards were fitted with the wrong value of C222 SMD. Perhaps we should all measure C222 before changing the capacitor. 73 -- David G4DMP Leeds, England, UK _______________________________________________ Elecraft mailing list Post to: [hidden email] 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 |
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In reply to this post by Ken Wagner K3IU
That was me .. My actual measurement was 0.985 microfarad when I checked the
RF board in S/N 195.... I rounded it up to 1 microfarad in my earlier report. Don K7FJ > Someone else here mentioned that C222 was 1 uF, but I don't remember who > it was. > > 73, > Ken K3IU >> _______________________________________________ Elecraft mailing list Post to: [hidden email] 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 |
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In reply to this post by David Pratt-2
> Or do Rev A RF boards have a lower value for C222 than that shown on the
> schematic? Early production K3 RF boards have a 1 uF capacitor instead of a 0.1 uF capacitor installed at C222. Yes, the published schematics show a 0.1 uF capacitor. The effect of the larger capacitor is to increase the TX waveform rise time to about 8 ms instead of 5 ms. Rev B RF boards have the correct 0.1 uF value installed. Sometime during Rev A RF board production, the value installed on the board was changed from 1 uF to 0.1 uF. Surface mount ceramic capacitors are not marked with a value, so you cannot tell which you have by visual inspection. You can determine if you have a 1 uF rather than a 0.1 uF by: 1) Measuring the capacitance if you have a capacitance meter. 2) Looking at the Tx output RF envelope on an oscilloscope or "station monitor" scope. If the fall time and the rise time look very similar in duration, you have the 0.1 uF cap. If the rise time is about 50% longer than the fall time, you have the 1 uF capacitor. You don't need an oscilloscope with an accurate time base to make this comparative measurement. If your oscilloscope has a low bandwidth (2 to 10 MHz), use the 160 meter band. 3) If you are concerned that your unit may have the 1 uF capacitor and you have no way to determine it otherwise, you can just replace it with the 0.1 uF part and sleep better at night :-) If you don't change it, you will not damage anything. Your K3 will just have slightly softer keying and an upcoming firmware adjustment of the keying time will be less accurate. 73, Lyle KK7P _______________________________________________ Elecraft mailing list Post to: [hidden email] 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 |
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In reply to this post by Don Ehrlich
I guess I didn't say... my K3 is #202
73, Ken KIU Don Ehrlich wrote: > That was me .. My actual measurement was 0.985 microfarad when I > checked the RF board in S/N 195.... I rounded it up to 1 microfarad in > my earlier report. > > Don K7FJ > > >> Someone else here mentioned that C222 was 1 uF, but I don't remember >> who it was. >> >> 73, >> Ken K3IU >>> > > Elecraft mailing list Post to: [hidden email] 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 |
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In reply to this post by David Pratt-2
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In reply to this post by David Pratt-2
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In reply to this post by Ken Wagner K3IU
Measured C222 in my K3 s/n 285 a while back and it is .1uf.
73, Joe W2KJ QRP, therefore I am _______________________________________________ Elecraft mailing list Post to: [hidden email] 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 |
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In reply to this post by David Pratt-2
David Pratt wrote:
> Elecraft says..... > "Some owners prefer a faster CW keying waveform rise time. The rise time > can be reduced from about 8 milliseconds to 5 milliseconds without > affecting the fall time by replacing capacitor C222 on the K3 main RF > board with a 0.1 uF capacitor. This change will also allow a future > firmware revision to further reduce rise time via a menu entry." > > But the schematics of the RF Board Rev. A4 (Sheet 3 of 4), dated > 9/19/07, show C222 as being 0.1 already. The instructions recommend > removing the existing 0.1 and replacing it with another 0.1 !! Surely > to reduce the rise time the existing capacitor should be shunted with > another one. > > Or do Rev A RF boards have a lower value for C222 than that shown on the > schematic? As I understand it, Wayne called for the modification earlier, but for some reason it didn't get reflected in production. That's why the schematic doesn't agree. The old value was 1 uf and it the new, correct value is 0.1 uf. -- 73, Vic, K2VCO Fresno CA http://www.qsl.net/k2vco _______________________________________________ Elecraft mailing list Post to: [hidden email] 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 |
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In reply to this post by KK7P
People,
8 ms.- 5 ms.= 3 ms., does it matter in any practical sense? I would really like to know who cares, and why? Can anyone hear the difference? Three-thousanths of a second? Not my old brain. 73, John, W2GW K3 #384 ----- Original Message ----- From: "Lyle Johnson" <[hidden email]> To: "Elecraft Reflector" <[hidden email]> Sent: Saturday, March 29, 2008 5:21 PM Subject: Re: [Elecraft] CW rise time mod >> Or do Rev A RF boards have a lower value for C222 than that shown on the >> schematic? > > Early production K3 RF boards have a 1 uF capacitor instead of a 0.1 uF > capacitor installed at C222. Yes, the published schematics show a 0.1 uF > capacitor. The effect of the larger capacitor is to increase the TX > waveform rise time to about 8 ms instead of 5 ms. > > Rev B RF boards have the correct 0.1 uF value installed. Sometime during > Rev A RF board production, the value installed on the board was changed > from 1 uF to 0.1 uF. > > Surface mount ceramic capacitors are not marked with a value, so you > cannot tell which you have by visual inspection. > > You can determine if you have a 1 uF rather than a 0.1 uF by: > > 1) Measuring the capacitance if you have a capacitance meter. > > 2) Looking at the Tx output RF envelope on an oscilloscope or "station > monitor" scope. If the fall time and the rise time look very similar in > duration, you have the 0.1 uF cap. If the rise time is about 50% longer > than the fall time, you have the 1 uF capacitor. You don't need an > oscilloscope with an accurate time base to make this comparative > measurement. If your oscilloscope has a low bandwidth (2 to 10 MHz), use > the 160 meter band. > > 3) If you are concerned that your unit may have the 1 uF capacitor and you > have no way to determine it otherwise, you can just replace it with the > 0.1 uF part and sleep better at night :-) > > If you don't change it, you will not damage anything. Your K3 will just > have slightly softer keying and an upcoming firmware adjustment of the > keying time will be less accurate. > > 73, > > Lyle KK7P > > _______________________________________________ > Elecraft mailing list > Post to: [hidden email] > 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: [hidden email] 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 |
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K3 CW rise time mod - Definition
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I would like to see someone please take this discussion one step
further and define the terms "hard" keying and "soft" keying, and describe how either an operator or someone listening would be able to discriminate between the two. My rig is #095 and I frequently contest in the 30-34 WPM range. How would I know if I'm guilty, if guilty is the right word, of "soft" keying?! Is this an issue only for those who are keying external amplifiers? 73, Gary, VE1RGB _______________________________________________ Elecraft mailing list Post to: [hidden email] 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: K3 CW rise time mod - Definition
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> I would like to see someone please take this discussion one step
> further and define the terms "hard" keying and "soft" keying, and describe > how either an operator or someone listening would be able to discriminate > between the two. Gary, this topic has been covered in great detail in nearly every ARRL Handbook for at least the last fifty years -- as well as other publications. Some of the most relevant material is covered in articles during the '40s and '50s by By Goodman and George Garmmer. Not all of the material pertaining to "optimum key-shaping" is accurate, but otherwise, the content is still accurate. Many of us do not like to be held hostage to one rise/fall setting as a "one size fits all" answer to our operating practices. With DSP-generated raised-cosine key shaping, it's now possible to tighten up key shaping at high CW speeds without appreciably consuming additional bandwidth. Paul, W9AC _______________________________________________ Elecraft mailing list Post to: [hidden email] 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 |
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Hi,
I worked a little bit of the SSB contest this weekend. I noticed last night I received the HI CUR warning a couple of times. The antenna is a 40m delta loop. I have checked the SWR and it never gets above 2:1 on the entire band. I also use the internal ATU to get it down to 1:1 when I'm transmitting. I am using a heil goldline with a HC5 cartridge for the mic and the mic gain was set to 3. I have never had the HI CUR warning occur while operating CW only in SSB. I looked up HI CUR in the manual and it says that it's usually to do with the radio trying to drive the finals at a higher output than what they are rated. I can connect a dummy load and set the radio to 10 watts then hold down the TUNE + DISPLAY buttons to put the radio in tune mode bypassing the ATU and the radio is putting out the correct amount of power which leads me to believe that the issue has something to do with the mic. Do you think I have the mic gain set too high? I have since backed it down to 1 and it hasn't done it since but it wasn't doing it everytime when it was set to 3 so I really don't know if that fixed it or not. Is there anyone else who uses a Heil Goldline with their K2? Am I even going down the right path troubleshooting wise? Or should I be looking at something else? 73 Matt W5LL _______________________________________________ Elecraft mailing list Post to: [hidden email] 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 |
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In reply to this post by P.B. Christensen
For what it is worth, I've just completed a Fourier analysis of the
original K3 and revised K3 waveforms presented by G4AON on his website. I was a bit concerned that the sharpening of the leading edge would adversely affect bandwidth and possibly generate clicks. Bottom line for the region of the spectrum between 0 and +/- 200 Hz there is a slight increase in average power (maybe 3 db) for the new "sharper" waveform. In the range of 200 to 300 Hz the average power increases maybe 10 db. However at this point the spectral energy is down 50 db anyhow. Beyond this 350 Hz, the spectrum energy of the "sharper" waveform actually falls off relative to the 8ms case. These conclusions are "eyeball averages" of the sawtooth looking output produced. The teeth go above and below the zero db level. I was pleasantly surprised. Apparently it isn't all in "rise time" it is also how that waveform is shaped. Here are the assumptions/limitations of the analysis. 1) Code used "Fast Fourier Transform" by M.F. Hajen 2) A single dit was modeled. 3) Both dits had the same length in the model (about 70ms representing about 20 wpm). 4) Waveforms were digitized in 1 ms steps. 5) The assumption that the waveforms given represented voltage and hence db was calculated by 20 log (amplitude/amplitude at 0 Hz) This doesn't reflect repeating dits or CW made up of dots and dashes. However, it is probably a worse case analysis or close to it. I don't have a web site to post on. There is a .jpg file available of results. Disclaimer I'm not an expert on this or on using the calculational tools. The output does at least agree with the position of the first zero point predicted by a sinx/x formula for a single pulse of near infinite rise time and same width. Clearly it doesn't represent other effects in the rig which affect spectrum. Like a lawyer once said: "I'm giving you some free advice, it is worth every penny paid for it" 73 de Brian/K3KO . Paul Christensen wrote: >> I would like to see someone please take this discussion one step >> further and define the terms "hard" keying and "soft" keying, and >> describe how either an operator or someone listening would be able to >> discriminate between the two. > > > Gary, this topic has been covered in great detail in nearly every ARRL > Handbook for at least the last fifty years -- as well as other > publications. Some of the most relevant material is covered in > articles during the '40s and '50s by By Goodman and George Garmmer. > Not all of the material pertaining to "optimum key-shaping" is > accurate, but otherwise, the content is still accurate. > > Many of us do not like to be held hostage to one rise/fall setting as > a "one size fits all" answer to our operating practices. With > DSP-generated raised-cosine key shaping, it's now possible to tighten > up key shaping at high CW speeds without appreciably consuming > additional bandwidth. > > Paul, W9AC > _______________________________________________ > Elecraft mailing list > Post to: [hidden email] > 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: [hidden email] 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 |
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I wonder if it will be possible to shorten rise times as the keying speed
increases without needing manual intervention. Only set the desired timing for one speed and the program fixes others automatically; or not as desired. David G3UNA _______________________________________________ Elecraft mailing list Post to: [hidden email] 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: K3 CW rise time mod - Definition
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In reply to this post by alsopb
Looking at the scope picture of a single Morse dit at G4AON's site http://www.astromag.co.uk/k3/k3_envelope2.jpg indicates the trailing edge might be a bigger contributor to potential clicks than the leading edge of the waveform. Note the upper right corner has a fairly "sharp" transition from "on" to "falling" and compare that to the nicely shaped transition at the upper left corner. >From all reports the K3 is more than acceptable but if any additional effort is put into CW shaping, the "upper right" transition may be a place to look. 73, ... Joe, W4TV > -----Original Message----- > From: [hidden email] > [mailto:[hidden email]] On Behalf Of Brian Alsop > Sent: Sunday, March 30, 2008 11:01 AM > Cc: [hidden email] > Subject: Re: [Elecraft] K3 CW rise time mod - Definition > > > For what it is worth, I've just completed a Fourier analysis of the > original K3 and revised K3 waveforms presented by G4AON on > his website. > > I was a bit concerned that the sharpening of the leading edge would > adversely affect bandwidth and possibly generate clicks. > > Bottom line for the region of the spectrum between 0 and +/- 200 Hz > there is a slight increase in average power (maybe 3 db) for the new > "sharper" waveform. In the range of 200 to 300 Hz the average power > increases maybe 10 db. However at this point the spectral energy is > down 50 db anyhow. Beyond this 350 Hz, the spectrum energy of the > "sharper" waveform actually falls off relative to the 8ms case. > > These conclusions are "eyeball averages" of the sawtooth > looking output > produced. The teeth go above and below the zero db level. > > I was pleasantly surprised. Apparently it isn't all in "rise > time" it > is also how that waveform is shaped. > > Here are the assumptions/limitations of the analysis. > 1) Code used "Fast Fourier Transform" by M.F. Hajen > 2) A single dit was modeled. > 3) Both dits had the same length in the model (about 70ms > representing > about 20 wpm). > 4) Waveforms were digitized in 1 ms steps. > 5) The assumption that the waveforms given represented > voltage and hence > db was calculated by 20 log (amplitude/amplitude at 0 Hz) > > This doesn't reflect repeating dits or CW made up of dots and > dashes. > However, it is probably a worse case analysis or close to it. > I don't have a web site to post on. There is a .jpg file > available of > results. > > Disclaimer > I'm not an expert on this or on using the calculational tools. The > output does at least agree with the position of the first zero point > predicted by a sinx/x formula for a single pulse of near > infinite rise > time and same width. Clearly it doesn't represent other > effects in the > rig which affect spectrum. > > Like a lawyer once said: "I'm giving you some free advice, it > is worth > every penny paid for it" > > 73 de Brian/K3KO > . > > Paul Christensen wrote: > > >> I would like to see someone please take this discussion > one step > >> further and define the terms "hard" keying and "soft" keying, and > >> describe how either an operator or someone listening would > be able to > >> discriminate between the two. > > > > > > Gary, this topic has been covered in great detail in nearly > every ARRL > > Handbook for at least the last fifty years -- as well as other > > publications. Some of the most relevant material is covered in > > articles during the '40s and '50s by By Goodman and George Garmmer. > > Not all of the material pertaining to "optimum key-shaping" is > > accurate, but otherwise, the content is still accurate. > > > > Many of us do not like to be held hostage to one rise/fall > setting as > > a "one size fits all" answer to our operating practices. With > > DSP-generated raised-cosine key shaping, it's now possible > to tighten > > up key shaping at high CW speeds without appreciably consuming > > additional bandwidth. > > > > Paul, W9AC > > _______________________________________________ > > Elecraft mailing list > > Post to: [hidden email] > > 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: [hidden email] > 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: [hidden email] 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 |
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In reply to this post by Gary Bartlett VE1RGB
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In reply to this post by Joe Subich, W4TV-3
Joe Subich, W4TV wrote:
> Looking at the scope picture of a single Morse dit at G4AON's > site http://www.astromag.co.uk/k3/k3_envelope2.jpg indicates > the trailing edge might be a bigger contributor to potential > clicks than the leading edge of the waveform. Note the upper > right corner has a fairly "sharp" transition from "on" to > "falling" and compare that to the nicely shaped transition at > the upper left corner. > > From all reports the K3 is more than acceptable but if any > additional effort is put into CW shaping, the "upper right" > transition may be a place to look. Wayne has looked into an alternative shaping of the keyed envelope with the intent of reducing the bandwidth of the keyed signal without increasing (and possibly decreasing) the overall rise/fall times. He's put this aside for now because he's working on higher priority projects like the subreceiver, but I expect that at some time we will see this. As K3KO also noted, it's not all in the rise/fall times. -- 73, Vic, K2VCO Fresno CA http://www.qsl.net/k2vco _______________________________________________ Elecraft mailing list Post to: [hidden email] 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 |
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