RE: [Elecraft] KPA100 - 80m poor quality SSB
On Thu, 13 Jan 2005 20:20:05 +0100, Sverre Holm wrote: -Original Message- There is an Errata from Elecraft which does not appeared to have made it onto their Web site yet. It is:- --- K2/100 MANUAL (Appendix G) ERRATA Rev. C-3, December 14, 2004 --- The errata is there now, see http://www.elecraft.com/manual/E740035E%20KPA100%20errata%20rev%20C-3.pdf 73 Sverre LA3ZA http://www.qsl.net/la3za/ Thanks for the information Sverre. Unfortunately:- a) The Errata is under the manual section, with no reference to it from the builders notes or elsewhere as far as I can see. b) The description in the Errata only mentions the changes to the KPA100 SWR foldback, nothing about curing the RFC3 resonance on 80m. I think that this is where your excellent index of modification takes over. 73 Stewart G3RXQ ___ 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] KPA100 - 80m poor quality SSB
You must have looked at a different errata sheet than I have. Item 3 talks about RFC3 and the resistor across it. The sheet is dated 12/14/2004 Stan Rife W5EWA Houston, TX K2 S/N 4216 Thanks for the information Sverre. Unfortunately:- a) The Errata is under the manual section, with no reference to it from the builders notes or elsewhere as far as I can see. b) The description in the Errata only mentions the changes to the KPA100 SWR foldback, nothing about curing the RFC3 resonance on 80m. I think that this is where your excellent index of modification takes over. 73 Stewart G3RXQ ___ 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] KPA100 - 80m poor quality SSB
On Thu, 13 Jan 2005 15:16:53 +0100, S55M wrote: So K2 Gentelmans...one question.. To fix RF switching problem in KPA100 there are 3 way's available (posted) 1. 12pF to ground from 1n4007's junction (just mooves a problem arround) 2. 1K resistor instead of RFC3 (affects RX preformance and marginal switching at high power levels) 3. Change RFC3 100uH with 1mH choke (dont know abt side effects but shure want to know the current rating of choke, cause i suppose must be at least 150mA or more?) Which way is the best for now? All kind of Help is Wellcome! Thanks in advance! S55M-Adi K2-3204 Adi, There is an Errata from Elecraft which does not appeared to have made it onto their Web site yet. It is:- --- K2/100 MANUAL (Appendix G) ERRATA Rev. C-3, December 14, 2004 --- a) A 1k resistor is fitted across RFC3. b) R4 in the HV bias supply is changed from 100k to 39k. The 1k resistor damps out the resonance on 80m in my KPA100, and I no longer experience the problem. 73 Stewart G3RXQ ___ 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] KPA100 - 80m poor quality SSB
Adi, Stewart Baker G3RXQ has also been fighting this problem and he sent me a note a week or so ago saying that he understood that on Dec 14th Eleraft issued an Errata for the KPA100 which changed R4 in the HV osc from 100k to 39k and ** added a 1k resistor in parallel with RFC3 ***. There was no reason given in the errata. Stewart put these changes into his KPA100 and so have I. Our 80 meter performance is now normal. These two changes are obviously aimed at fixing the T/R instability in some KPA100's caused by resonance in or near the 80 meter band involving RFC3 and the junction capacitance of D14. The 1k resistor spoils the Q of the resonant circuit without affecting receiver sensitivity or bias voltages and the change in R4 is probably to increase the design margin of the HV bias in some units with a 'lazy' oscillator. I had been waiting for an official Elecraft recommendation to the list but I finally got tired of waiting. In my opinion the 1k resistor across RFC3 is a very good solution. The change in R4 is not necessary if your bias voltage is already within the range recommended in the instructions. Don K7FJ --- So K2 Gentelmans...one question.. To fix RF switching problem in KPA100 there are 3 way's available (posted) 1. 12pF to ground from 1n4007's junction (just mooves a problem arround) 2. 1K resistor instead of RFC3 (affects RX preformance and marginal switching at high power levels) 3. Change RFC3 100uH with 1mH choke (dont know abt side effects but shure want to know the current rating of choke, cause i suppose must be at least 150mA or more?) Which way is the best for now? All kind of Help is Wellcome! Thanks in advance! S55M-Adi K2-3204 - Original Message - From: Stewart Baker [EMAIL PROTECTED] To: Don [EMAIL PROTECTED]; Elecraft Reflector elecraft@mailman.qth.net Sent: Wednesday, December 29, 2004 7:29 PM Subject: Re: [Elecraft] KPA100 - 80m poor quality SSB Although the 1k resistor mod seems to work there is a noticeable drop in received signals. Modeling the KPA100 T/R switching showed this additional loss. As a temporary measure until the official Elecraft modification comes out I have replaced RFC3 (100uH) with a 1mH RFC. My simulations show that the circuit resonance is now around 1.2MHz- maybe lower. Tried all bands, can't find a problem. 73 Stewart G3RXQ On Tue, 28 Dec 2004 18:11:15 GMT, Stewart Baker wrote: On Tue, 28 Dec 2004 09:36:00 -0800, Don wrote: Stewart, I have been in contact with Gary intermittantly since first coming across this problem in October. He assures me that Elecraft is working on a solution and will have something to say soon. Both the 12 pF fix and the 1000 ohm resistor fix have proved effective but are probably not the most elegant or foolproof ways of solving the problem. For instance, the 1000 ohm resistor alters the reverse bias on D14 in a way that makes the T/R switch marginal at high power levels. I suspect that Elecraft is taking their time and checking out all of the possible effects of design changes and mods before committing to a final solution. We will just have to be patient. Don K7FJ The guests having departed - the Turkey finally disposed of - the booze consumed - thoughts turned to Playing radio. I have been getting reports on 80m that my SSB signal had some edge to it. At first I put it down to RF feedback, but that was not the problem. I used my FT1000MP to listen to the 2nd harmonic of the 80m signal. Having read recent mails I first monitored the 3.5MHz signal and found the Buzz that others had reported. I then tried the following frequencies on 80 and noticed that as I increased the power control on the K2 the power output would suddenly jump, then when the control was turned ACW the power would reduce smoothly and then suddenly drop. It was also observable on the FT1000MP S-meter, accompanied by a click. It was like a form of hysteresis. All other bands gave smooth power control. The results were as follows:- 3.8MHz Low point=20W High point=70W Hysteresis=50W 3.7MHz Low point=25W High point=70W Hysteresis=45W 3.6MHz Low point=35W High point=70W Hysteresis=35W 3.5MHz Low point=40W High point=70W Hysteresis=30W Very unsatisfactory... I substituted a 1k resistor for RFC3, and all the 80m problems went away. Smooth power control on all bands and a better SSB signal on 80m. Many thanks to those who found/cured this problem that first showed itself on CW, I would certainly have spent a lot of time tracking this one down ! I would suggest that owners of K2/100's check to see that their rig does not exhibit these symptoms as it can make quite a big difference to transmitted signal quality. I, like a previous correspondent think that Elecraft should make some comment on this design problem, and it's solution. 73 Stewart G3RXQ Thanks for the Heads up Don. I will look forward
RE: [Elecraft] KPA100 - 80m poor quality SSB
-Original Message- There is an Errata from Elecraft which does not appeared to have made it onto their Web site yet. It is:- --- K2/100 MANUAL (Appendix G) ERRATA Rev. C-3, December 14, 2004 --- The errata is there now, see http://www.elecraft.com/manual/E740035E%20KPA100%20errata%20rev%20C-3.pdf 73 Sverre LA3ZA http://www.qsl.net/la3za/ ___ 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] KPA100 - 80m poor quality SSB
Although the 1k resistor mod seems to work there is a noticeable drop in received signals. Modeling the KPA100 T/R switching showed this additional loss. As a temporary measure until the official Elecraft modification comes out I have replaced RFC3 (100uH) with a 1mH RFC. My simulations show that the circuit resonance is now around 1.2MHz- maybe lower. Tried all bands, can't find a problem. 73 Stewart G3RXQ On Tue, 28 Dec 2004 18:11:15 GMT, Stewart Baker wrote: On Tue, 28 Dec 2004 09:36:00 -0800, Don wrote: Stewart, I have been in contact with Gary intermittantly since first coming across this problem in October. He assures me that Elecraft is working on a solution and will have something to say soon. Both the 12 pF fix and the 1000 ohm resistor fix have proved effective but are probably not the most elegant or foolproof ways of solving the problem. For instance, the 1000 ohm resistor alters the reverse bias on D14 in a way that makes the T/R switch marginal at high power levels. I suspect that Elecraft is taking their time and checking out all of the possible effects of design changes and mods before committing to a final solution. We will just have to be patient. Don K7FJ The guests having departed - the Turkey finally disposed of - the booze consumed - thoughts turned to Playing radio. I have been getting reports on 80m that my SSB signal had some edge to it. At first I put it down to RF feedback, but that was not the problem. I used my FT1000MP to listen to the 2nd harmonic of the 80m signal. Having read recent mails I first monitored the 3.5MHz signal and found the Buzz that others had reported. I then tried the following frequencies on 80 and noticed that as I increased the power control on the K2 the power output would suddenly jump, then when the control was turned ACW the power would reduce smoothly and then suddenly drop. It was also observable on the FT1000MP S-meter, accompanied by a click. It was like a form of hysteresis. All other bands gave smooth power control. The results were as follows:- 3.8MHz Low point=20W High point=70W Hysteresis=50W 3.7MHz Low point=25W High point=70W Hysteresis=45W 3.6MHz Low point=35W High point=70W Hysteresis=35W 3.5MHz Low point=40W High point=70W Hysteresis=30W Very unsatisfactory... I substituted a 1k resistor for RFC3, and all the 80m problems went away. Smooth power control on all bands and a better SSB signal on 80m. Many thanks to those who found/cured this problem that first showed itself on CW, I would certainly have spent a lot of time tracking this one down ! I would suggest that owners of K2/100's check to see that their rig does not exhibit these symptoms as it can make quite a big difference to transmitted signal quality. I, like a previous correspondent think that Elecraft should make some comment on this design problem, and it's solution. 73 Stewart G3RXQ Thanks for the Heads up Don. I will look forward to the official modification when it is released. 73 Stewart G3RXQ ___ 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] KPA100 - 80m poor quality SSB
Stewart, I have been in contact with Gary intermittantly since first coming across this problem in October. He assures me that Elecraft is working on a solution and will have something to say soon. Both the 12 pF fix and the 1000 ohm resistor fix have proved effective but are probably not the most elegant or foolproof ways of solving the problem. For instance, the 1000 ohm resistor alters the reverse bias on D14 in a way that makes the T/R switch marginal at high power levels. I suspect that Elecraft is taking their time and checking out all of the possible effects of design changes and mods before committing to a final solution. We will just have to be patient. Don K7FJ The guests having departed - the Turkey finally disposed of - the booze consumed - thoughts turned to Playing radio. I have been getting reports on 80m that my SSB signal had some edge to it. At first I put it down to RF feedback, but that was not the problem. I used my FT1000MP to listen to the 2nd harmonic of the 80m signal. Having read recent mails I first monitored the 3.5MHz signal and found the Buzz that others had reported. I then tried the following frequencies on 80 and noticed that as I increased the power control on the K2 the power output would suddenly jump, then when the control was turned ACW the power would reduce smoothly and then suddenly drop. It was also observable on the FT1000MP S-meter, accompanied by a click. It was like a form of hysteresis. All other bands gave smooth power control. The results were as follows:- 3.8MHz Low point=20W High point=70W Hysteresis=50W 3.7MHz Low point=25W High point=70W Hysteresis=45W 3.6MHz Low point=35W High point=70W Hysteresis=35W 3.5MHz Low point=40W High point=70W Hysteresis=30W Very unsatisfactory... I substituted a 1k resistor for RFC3, and all the 80m problems went away. Smooth power control on all bands and a better SSB signal on 80m. Many thanks to those who found/cured this problem that first showed itself on CW, I would certainly have spent a lot of time tracking this one down ! I would suggest that owners of K2/100's check to see that their rig does not exhibit these symptoms as it can make quite a big difference to transmitted signal quality. I, like a previous correspondent think that Elecraft should make some comment on this design problem, and it's solution. 73 Stewart G3RXQ ___ 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] KPA100 - 80m poor quality SSB
On Tue, 28 Dec 2004 09:36:00 -0800, Don wrote: Stewart, I have been in contact with Gary intermittantly since first coming across this problem in October. He assures me that Elecraft is working on a solution and will have something to say soon. Both the 12 pF fix and the 1000 ohm resistor fix have proved effective but are probably not the most elegant or foolproof ways of solving the problem. For instance, the 1000 ohm resistor alters the reverse bias on D14 in a way that makes the T/R switch marginal at high power levels. I suspect that Elecraft is taking their time and checking out all of the possible effects of design changes and mods before committing to a final solution. We will just have to be patient. Don K7FJ The guests having departed - the Turkey finally disposed of - the booze consumed - thoughts turned to Playing radio. I have been getting reports on 80m that my SSB signal had some edge to it. At first I put it down to RF feedback, but that was not the problem. I used my FT1000MP to listen to the 2nd harmonic of the 80m signal. Having read recent mails I first monitored the 3.5MHz signal and found the Buzz that others had reported. I then tried the following frequencies on 80 and noticed that as I increased the power control on the K2 the power output would suddenly jump, then when the control was turned ACW the power would reduce smoothly and then suddenly drop. It was also observable on the FT1000MP S-meter, accompanied by a click. It was like a form of hysteresis. All other bands gave smooth power control. The results were as follows:- 3.8MHz Low point=20W High point=70W Hysteresis=50W 3.7MHz Low point=25W High point=70W Hysteresis=45W 3.6MHz Low point=35W High point=70W Hysteresis=35W 3.5MHz Low point=40W High point=70W Hysteresis=30W Very unsatisfactory... I substituted a 1k resistor for RFC3, and all the 80m problems went away. Smooth power control on all bands and a better SSB signal on 80m. Many thanks to those who found/cured this problem that first showed itself on CW, I would certainly have spent a lot of time tracking this one down ! I would suggest that owners of K2/100's check to see that their rig does not exhibit these symptoms as it can make quite a big difference to transmitted signal quality. I, like a previous correspondent think that Elecraft should make some comment on this design problem, and it's solution. 73 Stewart G3RXQ Thanks for the Heads up Don. I will look forward to the official modification when it is released. 73 Stewart G3RXQ ___ 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
