That's worth a shot. I have a ~7 foot RG-213 patch cable from the back of the amp to the entry box. I don't have any more LMR-400 so I can't use that, but I do have quite a bit of 213 and will make a new patch cable. That's the only bit of the old system that's still remaining. - pjd
-----Original Message----- From: Vic Rosenthal <k2vco....@gmail.com> Sent: Monday, June 1, 2020 12:18 AM To: Peter Dougherty <li...@w2irt.net> Cc: j...@audiosystemsgroup.com; Elecraft@mailman.qth.net Subject: Re: [Elecraft] NOT the feedline (was KPA-1500 faulting on 6m; SWR issues) Are you using the same output connector on the KPA1500 for the dummy load and the antenna? Perhaps the problem is in one of the SO239s or in the KPA’s switching circuit? Victor 4X6GP > On 1 Jun 2020, at 4:30, Peter Dougherty <li...@w2irt.net> 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 > 10+ 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 > k2vco....@gmail.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
