Paul, please re-read what I wrote. The 90W figure is with the amp IN STANDBY! I wouldn't dream of putting more than about 35W into the KPA-1500. I generally like to run about 1200W on 6m, but even if I turn my K3s drive down to 20 Watts, it will STILL hard-fault regularly. NO AMOUNT OF DRIVE from the K3s will stop these problems. If the amp is set to deliver power it's going to fault on 6m, regardless of what the ATU is set for (bypass or inline), and the KPA will miss-read the SWR of the antenna system.
The resistance figure is 50.8 Ohms, and the reactance is -11 according to the AA-230. The only difference between "works reliably" and "faults out all the time" is one is a resistive-only load, the other has a reactive component. - pjd -----Original Message----- From: Paul Baldock <p...@paulbaldock.com> Sent: Sunday, May 31, 2020 10:06 PM To: Peter Dougherty <li...@w2irt.net>; elecraft@mailman.qth.net Subject: Re: [Elecraft] NOT the feedline (was KPA-1500 faulting on 6m; SWR issues) A few things I observe on my KPA 1500: On 6m the KPA1500 reads 1.3/1.4:1 into a perfect load. FYI it reads 1.2:1 in to a perfect load on 10M also, but 1.0:1 on all other bands.Elecraft have various excuses for this. 1500W its really pushing it on 6M. Way to much compression. I run mine at 1100W out with 38W drive. as you state 90W, that's way too much drive. As the amp warms up the output drops (on all bands), but I never exceed 38W drive on 6M. On FT8 I drive it to 500W out only, and the amp stays reasonably cool. On 6M I bypass the tuner as the real antenna SWR is less than 1.5:1, and I ignore what the KP1500 says it is. Try the amp the way I use it and see how it goes. Good luck - Paul KW7Y At 06:29 PM 5/31/2020, you wrote: >Many here suggested that it was most likely a feedline issue, and I >figured this was indeed a distinct possibility. > >So this afternoon I replaced the feedline. I now have about 80 feet of >brand new LMR-400, new 83-SP1 connectors (and an Amphenol adaptor at >the balun since I don't have any type-N connectors here). The AA-230 >ZOOM analyzer shows about 1.2:1 at 50.313, with resonance just below >the band. I'll fix that tomorrow, but 1.2 or 1.3:1 should be nothing to the KPA. > >The TDR screen looks very clean, just a tiny bump where the feedline >goes through the (new) bulkhead connector to get into the house. See: >https://www.dropbox.com/s/izcwvece7nt5f42/2020-05-31%2019.32.44.jpg?dl= >0 > >The SWR chart between 50.000 and 50.500: >https://www.dropbox.com/s/y2xh4l1lihy2ujr/2020-05-31%2021.23.29.jpg?dl= >0 > >Again, I know the antenna is resonant a bit low, but this should NOT be >a factor. So here's what's now going on. > >1) Into a Cantenna dummy load, with 25W of drive from the M3s, the >KPA-1500 is delivering 1075W and showing 1.4:1. No problem delivering >power and no faults. > >2) With input power increased, 35W of K3s drive gives 1375W at 1.5 into >the Cantenna. Again, no problem delivering power to the purely resistive load. >Why a 1.5:1, I don't know, but fine, whatever. I can TX for 15-20 >second periods without issue. > >3) When I switch over to the live antenna, with25 Watts of drive from >the K3s into the actual antenna and the amp faults out instantly in >bypass. When the amplifier is in bypass and the tuner is in bypass, and >when the K3s is delivering about 90W in FT8 mode, the front panel on >the KPA-1500 says the SWR is 1.9:1. When I press the TUNE button on the >radio, it's showing an SWR of 1.4:1. > >4) Amp in bypass, tuner inline, press TUNE button on the K3s and the >front panel of the KPA-1500 is showing a perfect 1.0:1 match. It SHOULD >work fine like this, right? > >5) Pressing ONLY the OPER/STBY button to put the amp in operate (KPA >tuner in and untouched since step 4), the amp SOMETIMES delivers power, >sometimes faults out, shows an SWR of 1.7:1. Pressing the OPER/STBY >button again to use only exciter power, and touching NOTHING ELSE, it's >back to 1.1:1 with 90W of K3s drive. > >6) There is basically no rhyme or reason why this is happening and it's >*somewhat* repeatable. The incredibly frustrating part is if I see a >needed station come up, I'll flick the amp's tuner in line and it says it's tuned. >Once WSJT-X keys the radio, 90 out of 100 times the amp will >hard-fault. If it doesn't fault on the first transmission, it >absolutely WILL on the second transmission. > >So I'm now at a complete loss to understand what's going on here. Amp >is fine into a resistive load. Brand-new antenna, brand new LMR-400 >feedline, brand new connectors, the KPA-1500 is faulting out the same >as it did on the >10+ year old 6M5 with a patchwork of feedlines. I can't see how this is >anything but a problem in the KPA-1500 (S/N 0398). > > - pjd > >-----Original Message----- >From: elecraft-boun...@mailman.qth.net ><elecraft-boun...@mailman.qth.net> On Behalf Of Jim Brown >Sent: Sunday, May 31, 2020 8:22 PM >To: elecraft@mailman.qth.net >Subject: Re: [Elecraft] KPA-1500 faulting on 6m; SWR issues > >On 5/31/2020 9:54 AM, Jim Miller wrote: > > Have you vetted your feedline at 1500w? Many times something might > > be good at low power and fail at 1500. > >This is good advice. Guys who do lots of portable setup say to always >check the coax first, which mostly means check for a connector that's >bad or badly installed. > >In general, if it doesn't say Amphenol or isn't stamped with a MIL spec >number, it's very likely to be poor quality. This includes barrels, >adapters, etc. Also make sure that every connector is" wrench tight." > >The advice to run it straight to a dummy load is right on -- if you >have one big enough. :) > >73, Jim K9YC >______________________________________________________________ >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...@w2irt.net > >______________________________________________________________ >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 >p...@paulbaldock.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
