PA DISS fault and relationship to SWR
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PA DISS fault and relationship to SWR
 
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Up until this weekend I had experienced 3 PA DISS faults with my new KPA500. I provided data to Elecraft and, after a fairly long and informative email exchange, I was told the fault is very rare and most likely caused by some problem at my station.
I developed a 10 frames per second data logger which polls and records data from the KPA500 serial interface as well as the ALARM signal available on the AUX port. The ALARM signal was also used as a trigger so that 'scope data could be time correlated with the logger data. CQ WPX CW contest seemed to be a good opportunity to gather data if the fault could be reproduced. After experiencing 5 PA DISS faults on 20 meters I abandoned the contest, looked at the recorded data, and ran some additional tests. The data show that PA dissipation (DC input power - RF output power) is strongly dependent of load SWR. That in itself is probably not surprising. What was surprising was that my KPA500, when operating into an antenna load that the KPA500 reports as 1.4:1 SWR, has a PA DISS of 500 W when producing 400 W output. What was more surprising is that, although the PA DISS fault is designed to trip at 400 W ("The PA Diss uses non-averaged data to do a comparison between the calculated power from PA voltage and PA current and the measured output power. If it is more than about 400 watts on four consecutive checks (each 8 mSec apart) then we declare the fault.") it did not trip for a key down test lasting several seconds. Sample data for different load condx shown below. None of these key down tests resulted in PA DISS fault. SteppIR: LP-100A SWR 1.58:1 PA DC Input / RF Out / PA DISS ^OS1; ^WS390 014; ^VI592 151; ^BN05; ^TM047; 893.92 390 503.92 ^OS1; ^WS390 014; ^VI590 151; ^BN05; ^FS00; 890.9 390 500.9 SteppIR: LP-100A SWR 1.38:1 ^OS1; ^WS428 013; ^VI585 143; ^BN05; ^TM039; 836.55 428 408.55 ^OS1; ^WS430 013; ^VI589 144; ^BN05; ^FS00; 848.16 430 418.16 Dummy load LP-100A SWR 1.08:1 ^OS1; ^WS440 011; ^VI598 132; ^BN05; ^FS00; 789.36 440 349.36 ^OS1; ^WS440 011; ^VI595 132; ^BN05; ^TM043; 785.4 440 345.4 Can someone at Elecraft please explain why PA DISS fault does not trip when key down PA DISS (calculated from WS and VI serial data) exceeds the 400 W threshold defined for this fault condition. When the PA DISS fault was seen in the contest it always happened during the first element of the CW transmission. Raw logger data, Excel data, and scope traces have been saved. KPA500 firmware is 1.54. 73, Andy k3wyc ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
Re: PA DISS fault and relationship to SWR
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I resumed contest operation after modifying my SteppIR driven element length for 20 m band. With KPA500 indicating 1.3:1 (LP-100A 1.38:1) I saw no more PA DISS faults.
If I had known that the KPA500 was this sensitive to load impedance I would, perhaps, have purchased the KAT500 tuner. However, I found nothing in the documentation that suggested the KPA500 would fault frequently with a reported SWR of 1.4:1 and with power and SWR never peaking in to the amber regions. 73, Andy k3wyc ________________________________ From: ANDY DURBIN <[hidden email]> Sent: Saturday, May 26, 2018 11:28 AM To: [hidden email] Subject: PA DISS fault and relationship to SWR Up until this weekend I had experienced 3 PA DISS faults with my new KPA500. I provided data to Elecraft and, after a fairly long and informative email exchange, I was told the fault is very rare and most likely caused by some problem at my station. I developed a 10 frames per second data logger which polls and records data from the KPA500 serial interface as well as the ALARM signal available on the AUX port. The ALARM signal was also used as a trigger so that 'scope data could be time correlated with the logger data. CQ WPX CW contest seemed to be a good opportunity to gather data if the fault could be reproduced. After experiencing 5 PA DISS faults on 20 meters I abandoned the contest, looked at the recorded data, and ran some additional tests. The data show that PA dissipation (DC input power - RF output power) is strongly dependent of load SWR. That in itself is probably not surprising. What was surprising was that my KPA500, when operating into an antenna load that the KPA500 reports as 1.4:1 SWR, has a PA DISS of 500 W when producing 400 W output. What was more surprising is that, although the PA DISS fault is designed to trip at 400 W ("The PA Diss uses non-averaged data to do a comparison between the calculated power from PA voltage and PA current and the measured output power. If it is more than about 400 watts on four consecutive checks (each 8 mSec apart) then we declare the fault.") it did not trip for a key down test lasting several seconds. Sample data for different load condx shown below. None of these key down tests resulted in PA DISS fault. SteppIR: LP-100A SWR 1.58:1 PA DC Input / RF Out / PA DISS ^OS1; ^WS390 014; ^VI592 151; ^BN05; ^TM047; 893.92 390 503.92 ^OS1; ^WS390 014; ^VI590 151; ^BN05; ^FS00; 890.9 390 500.9 SteppIR: LP-100A SWR 1.38:1 ^OS1; ^WS428 013; ^VI585 143; ^BN05; ^TM039; 836.55 428 408.55 ^OS1; ^WS430 013; ^VI589 144; ^BN05; ^FS00; 848.16 430 418.16 Dummy load LP-100A SWR 1.08:1 ^OS1; ^WS440 011; ^VI598 132; ^BN05; ^FS00; 789.36 440 349.36 ^OS1; ^WS440 011; ^VI595 132; ^BN05; ^TM043; 785.4 440 345.4 Can someone at Elecraft please explain why PA DISS fault does not trip when key down PA DISS (calculated from WS and VI serial data) exceeds the 400 W threshold defined for this fault condition. When the PA DISS fault was seen in the contest it always happened during the first element of the CW transmission. Raw logger data, Excel data, and scope traces have been saved. KPA500 firmware is 1.54. 73, Andy k3wyc ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
Re: PA DISS fault and relationship to SWR
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In reply to this post by ANDY DURBIN
Andy, I have seen this too. My remote tuner will sometimes quit with SWR in the 1.4 : 1 range. Sometimes it causes a KPA500 SWR Fault and sometimes not. My GUESS is that it depends on whether the impedance is <50 ohms or >50 ohms. The SWR does not tell you which.
Michael Blake [hidden email] On May 28, 2018, at 08:30 AM, ANDY DURBIN <[hidden email]> wrote: I resumed contest operation after modifying my SteppIR driven element length for 20 m band. With KPA500 indicating 1.3:1 (LP-100A 1.38:1) I saw no more PA DISS faults. If I had known that the KPA500 was this sensitive to load impedance I would, perhaps, have purchased the KAT500 tuner. However, I found nothing in the documentation that suggested the KPA500 would fault frequently with a reported SWR of 1.4:1 and with power and SWR never peaking in to the amber regions. 73, Andy k3wyc ________________________________ From: ANDY DURBIN <[hidden email]> Sent: Saturday, May 26, 2018 11:28 AM To: [hidden email] Subject: PA DISS fault and relationship to SWR Up until this weekend I had experienced 3 PA DISS faults with my new KPA500. I provided data to Elecraft and, after a fairly long and informative email exchange, I was told the fault is very rare and most likely caused by some problem at my station. I developed a 10 frames per second data logger which polls and records data from the KPA500 serial interface as well as the ALARM signal available on the AUX port. The ALARM signal was also used as a trigger so that 'scope data could be time correlated with the logger data. CQ WPX CW contest seemed to be a good opportunity to gather data if the fault could be reproduced. After experiencing 5 PA DISS faults on 20 meters I abandoned the contest, looked at the recorded data, and ran some additional tests. The data show that PA dissipation (DC input power - RF output power) is strongly dependent of load SWR. That in itself is probably not surprising. What was surprising was that my KPA500, when operating into an antenna load that the KPA500 reports as 1.4:1 SWR, has a PA DISS of 500 W when producing 400 W output. What was more surprising is that, although the PA DISS fault is designed to trip at 400 W ("The PA Diss uses non-averaged data to do a comparison between the calculated power from PA voltage and PA current and the measured output power. If it is more than about 400 watts on four consecutive checks (each 8 mSec apart) then we declare the fault.") it did not trip for a key down test lasting several seconds. Sample data for different load condx shown below. None of these key down tests resulted in PA DISS fault. SteppIR: LP-100A SWR 1.58:1 PA DC Input / RF Out / PA DISS ^OS1; ^WS390 014; ^VI592 151; ^BN05; ^TM047; 893.92 390 503.92 ^OS1; ^WS390 014; ^VI590 151; ^BN05; ^FS00; 890.9 390 500.9 SteppIR: LP-100A SWR 1.38:1 ^OS1; ^WS428 013; ^VI585 143; ^BN05; ^TM039; 836.55 428 408.55 ^OS1; ^WS430 013; ^VI589 144; ^BN05; ^FS00; 848.16 430 418.16 Dummy load LP-100A SWR 1.08:1 ^OS1; ^WS440 011; ^VI598 132; ^BN05; ^FS00; 789.36 440 349.36 ^OS1; ^WS440 011; ^VI595 132; ^BN05; ^TM043; 785.4 440 345.4 Can someone at Elecraft please explain why PA DISS fault does not trip when key down PA DISS (calculated from WS and VI serial data) exceeds the 400 W threshold defined for this fault condition. When the PA DISS fault was seen in the contest it always happened during the first element of the CW transmission. Raw logger data, Excel data, and scope traces have been saved. KPA500 firmware is 1.54. 73, Andy k3wyc ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
Re: PA DISS fault and relationship to SWR
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Thanks for the reply. Please note that I have no issue with high SWR faults. I have seen several FAULT 09 REFL HI events and they were all caused by an operator antenna switching error. PA DISS (FAULT 11) is not an SWR fault although it appears it can be induced by a load mismatch.
73, Andy k3wyc ________________________________ From: Michael Blake <[hidden email]> Sent: Monday, May 28, 2018 6:10 AM To: ANDY DURBIN Cc: [hidden email] Subject: Re: [Elecraft] PA DISS fault and relationship to SWR Andy, I have seen this too. My remote tuner will sometimes quit with SWR in the 1.4 : 1 range. Sometimes it causes a KPA500 SWR Fault and sometimes not. My GUESS is that it depends on whether the impedance is <50 ohms or >50 ohms. The SWR does not tell you which. Michael Blake [hidden email] ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
Re: PA DISS fault and relationship to SWR
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In reply to this post by ANDY DURBIN
Yes, I did understand that Andy. My GUESS was that the PA-DSS (efficiency) is sensitive to the actual load impedance. I suspect that the SWR fault, that I sometimes see, is also sensitive to low vs high impedance.
73 - Mike - K9JRI On May 28, 2018, at 09:24 AM, ANDY DURBIN <[hidden email]> wrote: Thanks for the reply. Please note that I have no issue with high SWR faults. I have seen several FAULT 09 REFL HI events and they were all caused by an operator antenna switching error. PA DISS (FAULT 11) is not an SWR fault although it appears it can be induced by a load mismatch. 73, Andy k3wyc From: Michael Blake <[hidden email]> Sent: Monday, May 28, 2018 6:10 AM To: ANDY DURBIN Cc: [hidden email] Subject: Re: [Elecraft] PA DISS fault and relationship to SWR Andy, I have seen this too. My remote tuner will sometimes quit with SWR in the 1.4 : 1 range. Sometimes it causes a KPA500 SWR Fault and sometimes not. My GUESS is that it depends on whether the impedance is <50 ohms or >50 ohms. The SWR does not tell you which. Michael Blake [hidden email] ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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