KPA1500 PA Current
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I’m in the process of checking out my amp. I have two dipoles (40 and 80). At resonance both show a 1.2:1 SWR with ATU totally bypassed. With ATU on, it remains bypassed on 80, but shows only the ATU ON LED on 40. In both cases the resultant SWR is 1.2:1. SWR measurements are from the KPA1500 display.
When I use the amp with my K3 and drive it up to 1500W, I am occasionally getting an excessive PA current fault at 63A. From a cold start it’s 60A, but as it warms up in contest usage I find the power drops off, so I have to adjust the K3 to bring it back up to 1500W. At that point the PA current goes over 60A. Interestingly, into a dummy load the 1500W point shows a PA current of only 55A. So the 1.2:1 SWR, be it via a bypassed ATU or using the ATU, is sufficient to raise the PA current eventually to excessive levels. Suggestions? I don’t want this to be flipping out during a contest. I also don’t want to reduce power into what should be a totally acceptable load. 73 Gary W2CS ______________________________________________________________ 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 |
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Send your email to Elecraft support. Can't hurt.
On Fri, Mar 15, 2019 at 12:26 PM Gary J Ferdinand <[hidden email]> wrote: > I’m in the process of checking out my amp. I have two dipoles (40 and > 80). At resonance both show a 1.2:1 SWR with ATU totally bypassed. With > ATU on, it remains bypassed on 80, but shows only the ATU ON LED on 40. In > both cases the resultant SWR is 1.2:1. SWR measurements are from the > KPA1500 display. > > When I use the amp with my K3 and drive it up to 1500W, I am occasionally > getting an excessive PA current fault at 63A. From a cold start it’s 60A, > but as it warms up in contest usage I find the power drops off, so I have > to adjust the K3 to bring it back up to 1500W. At that point the PA > current goes over 60A. > > Interestingly, into a dummy load the 1500W point shows a PA current of > only 55A. So the 1.2:1 SWR, be it via a bypassed ATU or using the ATU, is > sufficient to raise the PA current eventually to excessive levels. > > Suggestions? I don’t want this to be flipping out during a contest. I > also don’t want to reduce power into what should be a totally acceptable > load. > > 73 > > Gary W2CS > > > ______________________________________________________________ > 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 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 |
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In reply to this post by alaparos@w2cs.net
Gary,
Have you considered that there may be something in your antenna system that is heating up or otherwise changing with the 1500 watts power? The first thing I would suspect is a balun that is heating, or a connector that is not quite tight enough. Those kind of problems will not show up at lower power, but at 1500 watts may become troublesome. 73, Don W3FPR On 3/15/2019 3:25 PM, Gary J Ferdinand wrote: > I’m in the process of checking out my amp. I have two dipoles (40 and 80). At resonance both show a 1.2:1 SWR with ATU totally bypassed. With ATU on, it remains bypassed on 80, but shows only the ATU ON LED on 40. In both cases the resultant SWR is 1.2:1. SWR measurements are from the KPA1500 display. > > When I use the amp with my K3 and drive it up to 1500W, I am occasionally getting an excessive PA current fault at 63A. From a cold start it’s 60A, but as it warms up in contest usage I find the power drops off, so I have to adjust the K3 to bring it back up to 1500W. At that point the PA current goes over 60A. > > Interestingly, into a dummy load the 1500W point shows a PA current of only 55A. So the 1.2:1 SWR, be it via a bypassed ATU or using the ATU, is sufficient to raise the PA current eventually to excessive levels. > ______________________________________________________________ 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 |
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I believe its universal that as the KPA1500 warms
up the gain drops. I have mine set up on each band for around 1500WPEP when cold. If I operate it enough by the time the amp gets up to 70C its down to around 1300W. I try to operate the amp conservatively so I don't increase the input to raise the output back to 1500W, I just leave at 1300W,. The issue is in the amp, not in your antenna or feeder, balun etc. I had a SPE1.5K for a short time and this exhibited a similar effect. -Paul KW7Y At 02:10 PM 3/15/2019, Don Wilhelm wrote: >Gary, Have you considered that there may be >something in your antenna system that is heating >up or otherwise changing with the 1500 watts >power? The first thing I would suspect is a >balun that is heating, or a connector that is >not quite tight enough. Those kind of problems >will not show up at lower power, but at 1500 >watts may become troublesome. 73, Don W3FPR On >3/15/2019 3:25 PM, Gary J Ferdinand wrote: > >Iâm in the process of checking out my amp. I >have two dipoles (40 and 80). At resonance both >show a 1.2:1 SWR with ATU totally >bypassed. With ATU on, it remains bypassed on >80, but shows only the ATU ON LED on 40. In >both cases the resultant SWR is 1.2:1. SWR >measurements are from the KPA1500 display. > > >When I use the amp with my K3 and drive it up to >1500W, I am occasionally getting an excessive PA >current fault at 63A. From a cold start itâs >60A, but as it warms up in contest usage I find >the power drops off, so I have to adjust the K3 >to bring it back up to 1500W. At that point the >PA current goes over 60A. > > Interestingly, >into a dummy load the 1500W point shows a PA >current of only 55A. So the 1.2:1 SWR, be it >via a bypassed ATU or using the ATU, is >sufficient to raise the PA current eventually to >excessive levels. > >______________________________________________________________ >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 ______________________________________________________________ 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 |
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In reply to this post by alaparos@w2cs.net
On this list the subject comes up regularly. I have some issues when a feedline or antenna looks great, until I hit it with 1500 watts. Check you antennas and connectors, then come back let us know what you then find. Antennas and feedlines can fail or cause what you are seeing. 10-100 watts is simple, or looks to be so. With 1500 watts you will find issues you didn't know you had.
72 & 73, Bill K9YEQ FT’er for K2, KX1, KX3, KXPA100, KAT500, W2, etc. -----Original Message----- From: [hidden email] <[hidden email]> On Behalf Of Gary J Ferdinand Sent: Friday, March 15, 2019 2:26 PM To: elecraft <[hidden email]> Subject: [Elecraft] KPA1500 PA Current I’m in the process of checking out my amp. I have two dipoles (40 and 80). At resonance both show a 1.2:1 SWR with ATU totally bypassed. With ATU on, it remains bypassed on 80, but shows only the ATU ON LED on 40. In both cases the resultant SWR is 1.2:1. SWR measurements are from the KPA1500 display. When I use the amp with my K3 and drive it up to 1500W, I am occasionally getting an excessive PA current fault at 63A. From a cold start it’s 60A, but as it warms up in contest usage I find the power drops off, so I have to adjust the K3 to bring it back up to 1500W. At that point the PA current goes over 60A. Interestingly, into a dummy load the 1500W point shows a PA current of only 55A. So the 1.2:1 SWR, be it via a bypassed ATU or using the ATU, is sufficient to raise the PA current eventually to excessive levels. Suggestions? I don’t want this to be flipping out during a contest. I also don’t want to reduce power into what should be a totally acceptable load. 73 Gary W2CS ______________________________________________________________ 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 ______________________________________________________________ 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 |
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In reply to this post by Paul Baldock
Paul, I do not witness what you are seeing. You may also have an antenna issue, slight but problematic?
72 & 73, Bill K9YEQ FT’er for K2, KX1, KX3, KXPA100, KAT500, W2, etc. -----Original Message----- From: [hidden email] <[hidden email]> On Behalf Of Paul Baldock Sent: Friday, March 15, 2019 4:47 PM To: [hidden email]; Gary J Ferdinand <[hidden email]>; elecraft <[hidden email]> Subject: Re: [Elecraft] KPA1500 PA Current I believe its universal that as the KPA1500 warms up the gain drops. I have mine set up on each band for around 1500WPEP when cold. If I operate it enough by the time the amp gets up to 70C its down to around 1300W. I try to operate the amp conservatively so I don't increase the input to raise the output back to 1500W, I just leave at 1300W,. The issue is in the amp, not in your antenna or feeder, balun etc. I had a SPE1.5K for a short time and this exhibited a similar effect. -Paul KW7Y At 02:10 PM 3/15/2019, Don Wilhelm wrote: >Gary, Have you considered that there may be something in your antenna >system that is heating up or otherwise changing with the 1500 watts >power? The first thing I would suspect is a balun that is heating, or a >connector that is not quite tight enough. Those kind of problems will >not show up at lower power, but at 1500 watts may become troublesome. >73, Don W3FPR On >3/15/2019 3:25 PM, Gary J Ferdinand wrote: > I’m in the process of >checking out my amp. I have two dipoles (40 and 80). At resonance >both show a 1.2:1 SWR with ATU totally bypassed. With ATU on, it >remains bypassed on 80, but shows only the ATU ON LED on 40. In >both cases the resultant SWR is 1.2:1. SWR >measurements are from the KPA1500 display. > > When I use the amp with >my K3 and drive it up to 1500W, I am occasionally getting an excessive >PA current fault at 63A. From a cold start it’s 60A, but as it warms >up in contest usage I find the power drops off, so I have to adjust the >K3 to bring it back up to 1500W. At that point the PA current goes >over 60A. > > Interestingly, into a dummy load the 1500W point shows a >PA current of only 55A. So the 1.2:1 SWR, be it via a bypassed ATU or >using the ATU, is sufficient to raise the PA current eventually to >excessive levels. > >______________________________________________________________ >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 ______________________________________________________________ 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 ______________________________________________________________ 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 |
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In reply to this post by Don Wilhelm
This group is outstanding. Thank you Bob K4TAX for taking what must have been a fair amount of time walking thru the consequences of a 40- or 60-Ohm mismatch. That radiation resistance graph you attached is one I have used for decades!
Thanks Don W3FPR as well. There are several connectors in between the amp and the dipole’s center insulator. Since we have had several temperature swings of late, I shall firm them up when the rain stops. I’ll keep plugging. My KPA500/KAT500 combo had its own set of characteristics that I eventually learned, but not a PA current out of bounds. That one is new. Thanks everyone else for contributing. 73, Gary W2CS > On Mar 15, 2019, at 5:10 PM, Don Wilhelm <[hidden email]> wrote: > > Gary, > > Have you considered that there may be something in your antenna system that is heating up or otherwise changing with the 1500 watts power? > The first thing I would suspect is a balun that is heating, or a connector that is not quite tight enough. > > Those kind of problems will not show up at lower power, but at 1500 watts may become troublesome. > > 73, > Don W3FPR > > On 3/15/2019 3:25 PM, Gary J Ferdinand wrote: >> I’m in the process of checking out my amp. I have two dipoles (40 and 80). At resonance both show a 1.2:1 SWR with ATU totally bypassed. With ATU on, it remains bypassed on 80, but shows only the ATU ON LED on 40. In both cases the resultant SWR is 1.2:1. SWR measurements are from the KPA1500 display. >> When I use the amp with my K3 and drive it up to 1500W, I am occasionally getting an excessive PA current fault at 63A. From a cold start it’s 60A, but as it warms up in contest usage I find the power drops off, so I have to adjust the K3 to bring it back up to 1500W. At that point the PA current goes over 60A. >> Interestingly, into a dummy load the 1500W point shows a PA current of only 55A. So the 1.2:1 SWR, be it via a bypassed ATU or using the ATU, is sufficient to raise the PA current eventually to excessive levels. ______________________________________________________________ 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 |
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In reply to this post by Bill K9YEQ
No antenna issue here. No SWR variations when
antenna under continuous power (measured on a real SWR meter). Same effect into a high power cool dummy load. It's the amp without doubt. - Paul At 03:09 PM 3/15/2019, Bill Johnson wrote: >Paul, I do not witness what you are seeing. You >may also have an antenna issue, slight but problematic? > >72 & 73, >Bill >K9YEQ >FTâer for K2, KX1, KX3, KXPA100, KAT500, W2, etc. > >-----Original Message----- >From: [hidden email] ><[hidden email]> On Behalf Of Paul Baldock >Sent: Friday, March 15, 2019 4:47 PM >To: [hidden email]; Gary J Ferdinand ><[hidden email]>; elecraft <[hidden email]> >Subject: Re: [Elecraft] KPA1500 PA Current > >I believe its universal that as the KPA1500 >warms up the gain drops. I have mine set up on >each band for around 1500WPEP when cold. If I >operate it enough by the time the amp gets up to >70C its down to around 1300W. I try to >operate the amp conservatively so I don't >increase the input to raise the output back to 1500W, I just leave at 1300W,. > >The issue is in the amp, not in your antenna or feeder, balun etc. > >I had a SPE1.5K for a short time and this exhibited a similar effect. > >-Paul KW7Y > > >At 02:10 PM 3/15/2019, Don Wilhelm wrote: > >Gary, Have you considered that there may be something in your antenna > >system that is heating up or otherwise changing with the 1500 watts > >power? The first thing I would suspect is a balun that is heating, or a > >connector that is not quite tight enough. Those kind of problems will > >not show up at lower power, but at 1500 watts may become troublesome. > >73, Don W3FPR On > >3/15/2019 3:25 PM, Gary J Ferdinand wrote: > Iâm in the process of > >checking out my amp.mp. I have two dipoles (40 and 80). At resonance > >both show a 1.2:1 SWR with ATU totally bypassed. With ATU on, it > >remains bypassed on 80, but shows only the ATU ON LED on 40. In > >both cases the resultant SWR is 1.2:1. SWR > >measurements are from the KPA1500 display. > > When I use the amp with > >my K3 and drive it up to 1500W, I am occasionally getting an excessive > >PA current fault at 63A. From a cold start itâs 60A, but as it wa warms > >up in contest usage I find the power drops off, so I have to adjust the > >K3 to bring it back up to 1500W. At that point the PA current goes > >over 60A. > > Interestingly, into a dummy load the 1500W point shows a > >PA current of only 55A. So the 1.2:1 SWR, be it via a bypassed ATU or > >using the ATU, is sufficient to raise the PA current eventually to > >excessive levels. > > >______________________________________________________________ > >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 > >______________________________________________________________ >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 ______________________________________________________________ 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 |
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In reply to this post by alaparos@w2cs.net
"Have you considered that there may be something in your antenna system that is heating up or otherwise changing with the 1500 watts power? The first thing I would suspect is a balun that is heating, or a connector that is not quite tight enough."
After years in lab and flight test I came to appreciate the value of good instrumentation. The data below is a case of SWR run-away believed to be caused by heating of a mix 31 choke when an antenna matched for 160 m was used on 80m. The rapid but progressive rise in SWR is very different from what would be expected for an arc-over event. This data log shows parameters reported by my KAT500. The final two events are the KAT500 faulting and opening the KPA500 key line. 2019-02-21 06:56:02 New VSWR - VSWR 1.06; 2019-02-21 06:56:02 New VSWR - VSWR 1.00; 2019-02-21 06:56:02 New VSWR - VSWR 1.08; 2019-02-21 06:56:02 New VSWR - VSWR 1.07; 2019-02-21 06:56:03 New VSWR - VSWR 1.05; 2019-02-21 06:56:03 New VSWR - VSWR 1.08; 2019-02-21 06:56:03 New VSWR - VSWR 1.15; 2019-02-21 06:56:05 New VSWR - VSWR 1.19; 2019-02-21 06:56:05 New VSWR - VSWR 1.25; 2019-02-21 06:56:05 New VSWR - VSWR 1.30; 2019-02-21 06:56:05 New VSWR - VSWR 1.38; 2019-02-21 06:56:05 New VSWR - VSWR 1.44; 2019-02-21 06:56:05 New VSWR - VSWR 1.49; 2019-02-21 06:56:06 New VSWR - VSWR 1.58; 2019-02-21 06:56:06 New VSWR - VSWR 1.72; 2019-02-21 06:56:06 New VSWR - VSWR 1.85; 2019-02-21 06:56:06 New VSWR - VSWR 1.90; 2019-02-21 06:56:07 New VSWR - VSWR 2.00; 2019-02-21 06:56:07 New FLT - FLT4; 2019-02-21 06:56:07 New AMPI - AMPI1; 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 |
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In reply to this post by Paul Baldock
Contact tech support and they may be able to help you out. To me, I use toroid transformer and the output remains continuous on load. I did have a brief issue and could only load my EFHW at 100-500 watts but once above that the amp would fail. I took my trusty wrench when weather and snow conditions permitted, and tightened the connectors in the back yard and now all is back to normal. Visually, and with analyzer seemed to be ok, but with power, an issue.
Good luck. 73, Bill K9YEQ https://wrj-tech.com/ -----Original Message----- From: Paul Baldock <[hidden email]> Sent: Friday, March 15, 2019 5:39 PM To: Bill Johnson <[hidden email]>; [hidden email]; Gary J Ferdinand <[hidden email]>; elecraft <[hidden email]> Subject: RE: [Elecraft] KPA1500 PA Current No antenna issue here. No SWR variations when antenna under continuous power (measured on a real SWR meter). Same effect into a high power cool dummy load. It's the amp without doubt. - Paul At 03:09 PM 3/15/2019, Bill Johnson wrote: >Paul, I do not witness what you are seeing. You may also have an >antenna issue, slight but problematic? > >72 & 73, >Bill >K9YEQ >FT’er for K2, KX1, KX3, KXPA100, KAT500, W2, etc. > >-----Original Message----- >From: [hidden email] ><[hidden email]> On Behalf Of Paul Baldock >Sent: Friday, March 15, 2019 4:47 PM >To: [hidden email]; Gary J Ferdinand <[hidden email]>; >elecraft <[hidden email]> >Subject: Re: [Elecraft] KPA1500 PA Current > >I believe its universal that as the KPA1500 warms up the gain drops. I >have mine set up on each band for around 1500WPEP when cold. If I >operate it enough by the time the amp gets up to 70C its down to around >1300W. I try to operate the amp conservatively so I don't increase >the input to raise the output back to 1500W, I just leave at 1300W,. > >The issue is in the amp, not in your antenna or feeder, balun etc. > >I had a SPE1.5K for a short time and this exhibited a similar effect. > >-Paul KW7Y > > >At 02:10 PM 3/15/2019, Don Wilhelm wrote: > >Gary, Have you considered that there may be something in your antenna > >system that is heating up or otherwise changing with the 1500 watts > >power? The first thing I would suspect is a balun that is heating, or > >a connector that is not quite tight enough. Those kind of problems > >will not show up at lower power, but at 1500 watts may become troublesome. > >73, Don W3FPR On > >3/15/2019 3:25 PM, Gary J Ferdinand wrote: > I’m in the process of > >checking out my amp.mp. I have two dipoles (40 and 80). At > >resonance both show a 1.2:1 SWR with ATU totally bypassed. With ATU > >on, it remains bypassed on 80, but shows only the ATU ON LED on 40. In > >both cases the resultant SWR is 1.2:1. SWR > >measurements are from the KPA1500 display. > > When I use the amp > >with my K3 and drive it up to 1500W, I am occasionally getting an > >excessive PA current fault at 63A. From a cold start it’s 60A, > >but as it wa warms up in contest usage I find the power drops off, so > >I have to adjust the > >K3 to bring it back up to 1500W. At that point the PA current goes > >over 60A. > > Interestingly, into a dummy load the 1500W point shows > >a PA current of only 55A. So the 1.2:1 SWR, be it via a bypassed ATU > >or using the ATU, is sufficient to raise the PA current eventually to > >excessive levels. > > >______________________________________________________________ > >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 > >______________________________________________________________ >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 ______________________________________________________________ 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 |
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In reply to this post by ANDY DURBIN
Great graphing. Impressive. I know from experience going from 500 watts to 1500 will cause issues because of the higher power.
72 & 73, Bill K9YEQ FT'er for K2, KX1, KX3, KXPA100, KAT500, W2, etc. -----Original Message----- From: [hidden email] <[hidden email]> On Behalf Of Andy Durbin Sent: Friday, March 15, 2019 5:50 PM To: [hidden email] Subject: [Elecraft] KPA1500 PA Current "Have you considered that there may be something in your antenna system that is heating up or otherwise changing with the 1500 watts power? The first thing I would suspect is a balun that is heating, or a connector that is not quite tight enough." After years in lab and flight test I came to appreciate the value of good instrumentation. The data below is a case of SWR run-away believed to be caused by heating of a mix 31 choke when an antenna matched for 160 m was used on 80m. The rapid but progressive rise in SWR is very different from what would be expected for an arc-over event. This data log shows parameters reported by my KAT500. The final two events are the KAT500 faulting and opening the KPA500 key line. 2019-02-21 06:56:02 New VSWR - VSWR 1.06; 2019-02-21 06:56:02 New VSWR - VSWR 1.00; 2019-02-21 06:56:02 New VSWR - VSWR 1.08; 2019-02-21 06:56:02 New VSWR - VSWR 1.07; 2019-02-21 06:56:03 New VSWR - VSWR 1.05; 2019-02-21 06:56:03 New VSWR - VSWR 1.08; 2019-02-21 06:56:03 New VSWR - VSWR 1.15; 2019-02-21 06:56:05 New VSWR - VSWR 1.19; 2019-02-21 06:56:05 New VSWR - VSWR 1.25; 2019-02-21 06:56:05 New VSWR - VSWR 1.30; 2019-02-21 06:56:05 New VSWR - VSWR 1.38; 2019-02-21 06:56:05 New VSWR - VSWR 1.44; 2019-02-21 06:56:05 New VSWR - VSWR 1.49; 2019-02-21 06:56:06 New VSWR - VSWR 1.58; 2019-02-21 06:56:06 New VSWR - VSWR 1.72; 2019-02-21 06:56:06 New VSWR - VSWR 1.85; 2019-02-21 06:56:06 New VSWR - VSWR 1.90; 2019-02-21 06:56:07 New VSWR - VSWR 2.00; 2019-02-21 06:56:07 New FLT - FLT4; 2019-02-21 06:56:07 New AMPI - AMPI1; 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 ______________________________________________________________ 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 |
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Should read can, not "will".
73, Bill K9YEQ https://wrj-tech.com/ -----Original Message----- From: [hidden email] <[hidden email]> On Behalf Of Bill Johnson Sent: Friday, March 15, 2019 5:55 PM To: Andy Durbin <[hidden email]>; [hidden email] Subject: Re: [Elecraft] KPA1500 PA Current Great graphing. Impressive. I know from experience going from 500 watts to 1500 will cause issues because of the higher power. 72 & 73, Bill K9YEQ FT'er for K2, KX1, KX3, KXPA100, KAT500, W2, etc. -----Original Message----- From: [hidden email] <[hidden email]> On Behalf Of Andy Durbin Sent: Friday, March 15, 2019 5:50 PM To: [hidden email] Subject: [Elecraft] KPA1500 PA Current "Have you considered that there may be something in your antenna system that is heating up or otherwise changing with the 1500 watts power? The first thing I would suspect is a balun that is heating, or a connector that is not quite tight enough." After years in lab and flight test I came to appreciate the value of good instrumentation. The data below is a case of SWR run-away believed to be caused by heating of a mix 31 choke when an antenna matched for 160 m was used on 80m. The rapid but progressive rise in SWR is very different from what would be expected for an arc-over event. This data log shows parameters reported by my KAT500. The final two events are the KAT500 faulting and opening the KPA500 key line. 2019-02-21 06:56:02 New VSWR - VSWR 1.06; 2019-02-21 06:56:02 New VSWR - VSWR 1.00; 2019-02-21 06:56:02 New VSWR - VSWR 1.08; 2019-02-21 06:56:02 New VSWR - VSWR 1.07; 2019-02-21 06:56:03 New VSWR - VSWR 1.05; 2019-02-21 06:56:03 New VSWR - VSWR 1.08; 2019-02-21 06:56:03 New VSWR - VSWR 1.15; 2019-02-21 06:56:05 New VSWR - VSWR 1.19; 2019-02-21 06:56:05 New VSWR - VSWR 1.25; 2019-02-21 06:56:05 New VSWR - VSWR 1.30; 2019-02-21 06:56:05 New VSWR - VSWR 1.38; 2019-02-21 06:56:05 New VSWR - VSWR 1.44; 2019-02-21 06:56:05 New VSWR - VSWR 1.49; 2019-02-21 06:56:06 New VSWR - VSWR 1.58; 2019-02-21 06:56:06 New VSWR - VSWR 1.72; 2019-02-21 06:56:06 New VSWR - VSWR 1.85; 2019-02-21 06:56:06 New VSWR - VSWR 1.90; 2019-02-21 06:56:07 New VSWR - VSWR 2.00; 2019-02-21 06:56:07 New FLT - FLT4; 2019-02-21 06:56:07 New AMPI - AMPI1; 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 ______________________________________________________________ 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 ______________________________________________________________ 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 |
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In reply to this post by alaparos@w2cs.net
Hi Gary,
I haven’t seen that problem unless the SWR was at least 1.4:1. However, it’s possible you have hit just the wrong phase angle. If your 1.2 SWR resulted in a load impedance of 42 Ohms, the current could go up 20 percent. On the other hand, 55 A into 50 Ohms sounds a bit high. Make sure the voltage isn’t dropping more than a couple Volts. 73, Scott K9MA ---------- Scott Ellington --- via iPad > On Mar 15, 2019, at 1:25 PM, Gary J Ferdinand <[hidden email]> wrote: > > I’m in the process of checking out my amp. I have two dipoles (40 and 80). At resonance both show a 1.2:1 SWR with ATU totally bypassed. With ATU on, it remains bypassed on 80, but shows only the ATU ON LED on 40. In both cases the resultant SWR is 1.2:1. SWR measurements are from the KPA1500 display. > > When I use the amp with my K3 and drive it up to 1500W, I am occasionally getting an excessive PA current fault at 63A. From a cold start it’s 60A, but as it warms up in contest usage I find the power drops off, so I have to adjust the K3 to bring it back up to 1500W. At that point the PA current goes over 60A. > > Interestingly, into a dummy load the 1500W point shows a PA current of only 55A. So the 1.2:1 SWR, be it via a bypassed ATU or using the ATU, is sufficient to raise the PA current eventually to excessive levels. > > Suggestions? I don’t want this to be flipping out during a contest. I also don’t want to reduce power into what should be a totally acceptable load. > > 73 > > Gary W2CS > > > ______________________________________________________________ > 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 ______________________________________________________________ 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 |
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Try 1000 watts for one month. Then 500 watts for the next month. Don’t tell anyone.
Unless you are trying to get that last country for your stats you won’t see any difference in your enjoyment and contact ratio. How often do we turn our receivers, stereos, ovens, microwaves, irons, or even car engines up to their max just “because we can”? Not trying to start a flame war here but to me it does make sense to give our equipment some breathing room? Yesterday while monitoring a group of guys around Michigan on 75 meters one of them dropped down from his KW to 12 watts and everyone was amazed he was still 20 dB over S9. They were over 100 miles apart too. Many of my friends have over 300 countries or have worked all counties and have never used over 500 watts, mostly 100 watts. Yes, it is good to experiment to find out why this is occurring, but after that give your amp some room to breathe. I watch this list for education and haven’t ever seen a rating of how high the Elecraft 1500 watt amp is tested at, what is its actual max output and for how long. I would guess that if it’s designed to handle 3000 watts then 1500 watts is conservative and this problem shouldn’t be happening. If it is tested and burned in at 2000 watts then it is being pushed and heating might be a problem on some amps. I have watched a few other comments on the Elecraft 100 watt amp and they have troubles getting an actual 100 watts out all the time too. Rain, ice, and other factors change things too. Isn’t this hobby fun? Just a thought. Dave K8WPE David J. Wilcox K8WPE’s iPad > On Mar 15, 2019, at 9:27 PM, K9MA <[hidden email]> wrote: > > Hi Gary, > > I haven’t seen that problem unless the SWR was at least 1.4:1. However, it’s possible you have hit just the wrong phase angle. If your 1.2 SWR resulted in a load impedance of 42 Ohms, the current could go up 20 percent. On the other hand, 55 A into 50 Ohms sounds a bit high. Make sure the voltage isn’t dropping more than a couple Volts. > > 73, > Scott K9MA > > ---------- > > Scott Ellington > > --- via iPad > >> On Mar 15, 2019, at 1:25 PM, Gary J Ferdinand <[hidden email]> wrote: >> >> I’m in the process of checking out my amp. I have two dipoles (40 and 80). At resonance both show a 1.2:1 SWR with ATU totally bypassed. With ATU on, it remains bypassed on 80, but shows only the ATU ON LED on 40. In both cases the resultant SWR is 1.2:1. SWR measurements are from the KPA1500 display. >> >> When I use the amp with my K3 and drive it up to 1500W, I am occasionally getting an excessive PA current fault at 63A. From a cold start it’s 60A, but as it warms up in contest usage I find the power drops off, so I have to adjust the K3 to bring it back up to 1500W. At that point the PA current goes over 60A. >> >> Interestingly, into a dummy load the 1500W point shows a PA current of only 55A. So the 1.2:1 SWR, be it via a bypassed ATU or using the ATU, is sufficient to raise the PA current eventually to excessive levels. >> >> Suggestions? I don’t want this to be flipping out during a contest. I also don’t want to reduce power into what should be a totally acceptable load. >> >> 73 >> >> Gary W2CS >> >> >> ______________________________________________________________ >> 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 > > ______________________________________________________________ > 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 ______________________________________________________________ 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 |
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Refreshing attitude, Dave!
James Forsman [hidden email] https://jrquark.smugmug.com/HamRadio > On Mar 16, 2019, at 5:13 AM, David Wilcox via Elecraft <[hidden email]> wrote: > > Try 1000 watts for one month. Then 500 watts for the next month. Don’t tell anyone. ______________________________________________________________ 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 |
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In reply to this post by alaparos@w2cs.net
In the same vein: I recently tried out my new 2m 1500w sspa at 750w
in SSB and stations on my net only stated a slight increase in signal 100 miles away vs running 130w. That should have indicated more than one s-unit stronger (10Log (750/130)=7.6 dB). Definitely a "knee" in signal strength where change is most significant and where change above is not so much. HF that should even be more compressed. Raising antenna ten feet above tree top is worth at least 10-dB in signal improvement at VHF (and way more as freq is increased into UHF+). I can lower my 2m array to 4-foot AGL by use of a winch. Going from there to about 40-feet (tree top) is worth maybe 5-dB. 73, Ed - KL7UW http://www.kl7uw.com Dubus-NA Business mail: [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 |
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On 3/16/2019 2:31 PM, Edward R Cole wrote:
> In the same vein: I recently tried out my new 2m 1500w sspa at 750w > in SSB and stations on my net only stated a slight increase in signal > 100 miles away vs running 130w. That should have indicated more than > one s-unit stronger (10Log (750/130)=7.6 dB). > > Definitely a "knee" in signal strength where change is most > significant and where change above is not so much. HF that should > even be more compressed. What you're calling a "knee" is better described as a combination of receiver AGC, perception of loudness and signal to noise by our ear/brain function, and how various signal characteristics combine to provide speech intelligibility. A change in OVERALL loudness of 6-10 dB is perceived as twice (or half) as loud when the signal is well above the noise, and 1 dB is about the smallest change IN OVERALL loudness that untrained listeners can perceive. But when the signal is close to the noise, a few dB change in the signal to noise ratio often makes a big difference in speech intelligibility. And what I learned in my professional life and have been teaching the ham community for more than ten years is that speech intelligibility is most strongly dependent on components in the 800 Hz to 3 kHz range, with higher frequencies making a small additional contribution. Roughly half of the ENERGY in speech is below 500 Hz, but this sound makes almost no contribution to speech intelligibility. SO -- using TXEQ to remove that sound is the equivalent of doubling the effective talk power (3dB)! This is why I've always recommended setting TXEQ for max cut in the three lowest bands, 6 dB cut in the 4th band (400 Hz), and a small boost (3-6 dB) in the top two bands. Careful use of good speech compression can add another 10dB of talk power, so the combination of EQ and compression can improve signal to noise by 13 dB, which is equivalent to multiplying transmitter power by 20! > Raising antenna ten feet above tree top is worth at least 10-dB in > signal improvement at VHF (and way more as freq is increased into > UHF+). I can lower my 2m array to 4-foot AGL by use of a winch. Going > from there to about 40-feet (tree top) is worth maybe 5-dB. Yes, and height above ground can matter a LOT on the HF bands. http://k9yc.com/AntennaPlanning.pdf 73, Jim K9YC ______________________________________________________________ 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 |
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In reply to this post by Elecraft mailing list
By and large the response to my technical question regarding the behavior of my KPA1500 have been good, technical information and hints. Your posting, Dave, is of the form of a lecture and comes across as anything but responsive to the topic at hand. Whether I wish to squeeze the last dB out of my signal or not is not yours to comment on.
Please confine your postings to being responsive to the thread. 73, Gary W2CS > On Mar 16, 2019, at 5:13 AM, David Wilcox <[hidden email]> wrote: > > Try 1000 watts for one month. Then 500 watts for the next month. Don’t tell anyone. > > Unless you are trying to get that last country for your stats you won’t see any difference in your enjoyment and contact ratio. How often do we turn our receivers, stereos, ovens, microwaves, irons, or even car engines up to their max just “because we can”? Not trying to start a flame war here but to me it does make sense to give our equipment some breathing room? > > Yesterday while monitoring a group of guys around Michigan on 75 meters one of them dropped down from his KW to 12 watts and everyone was amazed he was still 20 dB over S9. They were over 100 miles apart too. > > Many of my friends have over 300 countries or have worked all counties and have never used over 500 watts, mostly 100 watts. > > Yes, it is good to experiment to find out why this is occurring, but after that give your amp some room to breathe. I watch this list for education and haven’t ever seen a rating of how high the Elecraft 1500 watt amp is tested at, what is its actual max output and for how long. I would guess that if it’s designed to handle 3000 watts then 1500 watts is conservative and this problem shouldn’t be happening. If it is tested and burned in at 2000 watts then it is being pushed and heating might be a problem on some amps. I have watched a few other comments on the Elecraft 100 watt amp and they have troubles getting an actual 100 watts out all the time too. Rain, ice, and other factors change things too. Isn’t this hobby fun? > > Just a thought. > > Dave K8WPE > > David J. Wilcox K8WPE’s iPad > >> On Mar 15, 2019, at 9:27 PM, K9MA <[hidden email]> wrote: comeer, it’s possible you have hit just the wrong phase angle. If your 1.2 SWR resulted in a load impedance of 42 Ohms, the current could go up 20 percent. On the other hand, 55 A into 50 Ohms sounds a bit high. Make sure the voltage isn’t dropping more than a couple Volts. >> >> 73, >> Scott K9MA >> >> ---------- >> >> Scott Ellington >> >> --- via iPad >> >>> On Mar 15, 2019, at 1:25 PM, Gary J Ferdinand <[hidden email]> wrote: >>> >>> I’m in the process of checking out my amp. I have two dipoles (40 and 80). At resonance both show a 1.2:1 SWR with ATU totally bypassed. With ATU on, it remains bypassed on 80, but shows only the ATU ON LED on 40. In both cases the resultant SWR is 1.2:1. SWR measurements are from the KPA1500 display. >>> >>> When I use the amp with my K3 and drive it up to 1500W, I am occasionally getting an excessive PA current fault at 63A. From a cold start it’s 60A, but as it warms up in contest usage I find the power drops off, so I have to adjust the K3 to bring it back up to 1500W. At that point the PA current goes over 60A. >>> >>> Interestingly, into a dummy load the 1500W point shows a PA current of only 55A. So the 1.2:1 SWR, be it via a bypassed ATU or using the ATU, is sufficient to raise the PA current eventually to excessive levels. >>> >>> Suggestions? I don’t want this to be flipping out during a contest. I also don’t want to reduce power into what should be a totally acceptable load. >>> >>> 73 >>> >>> Gary W2CS >>> >>> >>> ______________________________________________________________ >>> 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 >> >> ______________________________________________________________ >> 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 > ______________________________________________________________ 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 |
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In reply to this post by Jim Brown-10
From my formal training in audio tech, a 10 dB gain is needed to get a perceived doubling of audio. With an audio sampler device listening for volume levels recording on a level meter, try doubling the output level on your output device according to your sampling device and at the same time listening to what you think doubling actually appears to you, then compare mentally the difference to what you perceive is real. Totally different in my experience. I could never figure out what was double while looking at the actual controls and what was factually happening and what my hearing and brain perceived without measuring and metering
73, Bill K9YEQ https://wrj-tech.com/ -----Original Message----- From: [hidden email] <[hidden email]> On Behalf Of Jim Brown Sent: Saturday, March 16, 2019 6:30 PM To: [hidden email] Subject: Re: [Elecraft] KPA1500 PA Current On 3/16/2019 2:31 PM, Edward R Cole wrote: > In the same vein: I recently tried out my new 2m 1500w sspa at 750w > in SSB and stations on my net only stated a slight increase in signal > 100 miles away vs running 130w. That should have indicated more than > one s-unit stronger (10Log (750/130)=7.6 dB). > > Definitely a "knee" in signal strength where change is most > significant and where change above is not so much. HF that should > even be more compressed. What you're calling a "knee" is better described as a combination of receiver AGC, perception of loudness and signal to noise by our ear/brain function, and how various signal characteristics combine to provide speech intelligibility. A change in OVERALL loudness of 6-10 dB is perceived as twice (or half) as loud when the signal is well above the noise, and 1 dB is about the smallest change IN OVERALL loudness that untrained listeners can perceive. But when the signal is close to the noise, a few dB change in the signal to noise ratio often makes a big difference in speech intelligibility. And what I learned in my professional life and have been teaching the ham community for more than ten years is that speech intelligibility is most strongly dependent on components in the 800 Hz to 3 kHz range, with higher frequencies making a small additional contribution. Roughly half of the ENERGY in speech is below 500 Hz, but this sound makes almost no contribution to speech intelligibility. SO -- using TXEQ to remove that sound is the equivalent of doubling the effective talk power (3dB)! This is why I've always recommended setting TXEQ for max cut in the three lowest bands, 6 dB cut in the 4th band (400 Hz), and a small boost (3-6 dB) in the top two bands. Careful use of good speech compression can add another 10dB of talk power, so the combination of EQ and compression can improve signal to noise by 13 dB, which is equivalent to multiplying transmitter power by 20! > Raising antenna ten feet above tree top is worth at least 10-dB in > signal improvement at VHF (and way more as freq is increased into > UHF+). I can lower my 2m array to 4-foot AGL by use of a winch. Going > from there to about 40-feet (tree top) is worth maybe 5-dB. Yes, and height above ground can matter a LOT on the HF bands. http://k9yc.com/AntennaPlanning.pdf 73, Jim K9YC ______________________________________________________________ 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 ______________________________________________________________ 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 |
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In reply to this post by Hank Garretson
At 1500W my Expert 2k-FA reports 50-52A at 49 V. About 55A at 1800W. The
Expert saturates at 2 KW. You may check out the SWR with a reputable meter. Often multiple meters show different values on different frequencies. For instance at my station LP100 shows 1.4:1, 2k-fa shows 1.2:1, and K3 shows 1.8:1. But no problem in the end. Ignacy, NO9E -- Sent from: http://elecraft.365791.n2.nabble.com/ ______________________________________________________________ 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 |
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