Re: [Elecraft] K2/100 down power on 20M
Hi Jerry, I agree that the relatively low TX power output on 20M originates in the KPA100 module. Did you build that module and install it yourself? The LPA circuit in the base K2 seems to operating normally, and your peaking of the BPF confirms that. If you have capability to sweep the 20M/30M LPF section on the KPA100 for insertion loss, that would provide more insight. However, those LPF sections are also inline when the KPA100 is nominally bypassed - it's only the amplifier circuit that is bypassed. If there was a significant problem in the LPF on the KPA100, it would have been evident in your tests on the 10 watt TX power setting. I would check the ALC indication on each band, but set the Power control for 100 watts rather than full clockwise rotation. You could also monitor the ALC voltage on the Control board as you change bands to see if for some reason the ALC control is reducing TX power on 20 meters. There is no band-dependent circuitry in the ALC system, but the SWR forward/reverse power detection circuit on the KPA100 does have a trimmer cap to balance the bridge. It would be unlikely for a resonance condition in the bridge to cause an elevated VRFDET voltage on one band alone, but I am curious if the ALC system is doing something odd on 20 meters only. 73, Mike, K8CN __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] K2/100 down power on 20M
OK, With a dummy load - actually a 500W Bird 30dB attenuator - the displayed power out came up to 78W. I tried adjusting the bandpass filter - it was already spot on. They use one filter for 40M and 30M, and you go back & forth between the two. It was already perfectly peaked & tweaked. What about the KPA100? I turned the power down to 10W, taking it out of the circuit. 20M - 9.6W 30M - 10.23W With power set to 40W: 20M - 41.7W 30M - 42.5W With power set to 60W: 20M - 56.8W 30M - 62.5W With power set to 80W: 20M - 71W 30M - 77.6W With power set to 100W: 20M - 78.6W 30M - 91.7W With power set to 110W: 20M - 78.6W 30M - 98.5W I suspect that the problem is in the KPA-100. Maybe a wrong value in the LPF? Power out with control set fully clockwise, into the dummy load, measured by the Telepost: 80M - 120W 40M - 104W 30M - 97.7W 20M - 79.4W 17M - 98.3W 15M - 88W 10M - 74.5W Interesting, according to the KPA100 manual, 20M and 17M share an LPF. If it was out of whack, I'd expect 17M to be MORE effected than 20. - Jerry, KF6VB On 2024-03-16 09:10, Joe Subich, W4TV wrote: But before that, I should redo the test with a dummy load. Yes. And it's not just gain decreasing with rising frequency, because it does 92W on 15M, 76W on 10M. First suspicion ... check the alignment of your bandpass filters. 73, ... Joe, W4TV On 3/16/2024 11:56 AM, jerry wrote: Hello, I've been doing a bit of operation with my K2 lately. It really is a joy on CW, and it fits perfectly under my big computer monitors. But I have noticed On 40M, it does 101W out. But on 20, only 63W. This is measured with a Telepost LP-100A vector wattmeter. The SWR is 1.4 to 1. And it's not just gain decreasing with rising frequency, because it does 92W on 15M, 76W on 10M. Guess it's time to get out the schematics... But before that, I should redo the test with a dummy load. - Jerry, KF6VB __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to li...@subich.com __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] K2/100 down power on 20M
But before that, I should redo the test with a dummy load. Yes. And it's not just gain decreasing with rising frequency, because it does 92W on 15M, 76W on 10M. First suspicion ... check the alignment of your bandpass filters. 73, ... Joe, W4TV On 3/16/2024 11:56 AM, jerry wrote: Hello, I've been doing a bit of operation with my K2 lately. It really is a joy on CW, and it fits perfectly under my big computer monitors. But I have noticed On 40M, it does 101W out. But on 20, only 63W. This is measured with a Telepost LP-100A vector wattmeter. The SWR is 1.4 to 1. And it's not just gain decreasing with rising frequency, because it does 92W on 15M, 76W on 10M. Guess it's time to get out the schematics... But before that, I should redo the test with a dummy load. - Jerry, KF6VB __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to li...@subich.com __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
[Elecraft] K2/100 down power on 20M
Hello, I've been doing a bit of operation with my K2 lately. It really is a joy on CW, and it fits perfectly under my big computer monitors. But I have noticed On 40M, it does 101W out. But on 20, only 63W. This is measured with a Telepost LP-100A vector wattmeter. The SWR is 1.4 to 1. And it's not just gain decreasing with rising frequency, because it does 92W on 15M, 76W on 10M. Guess it's time to get out the schematics... But before that, I should redo the test with a dummy load. - Jerry, KF6VB __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
