Ignacy, for many years I was using a legal limit tube amp in combination with a manual tuner. For 20m and up, where the antenna has low swr and broad bandwidth, I would put the tuner in bypass position. For 40m the tuner would be active and I would manually adjust it, which didn't happen very often as I would mostly stay in the cw portion of the band. The amp could perhaps have handled the swr on 40m without a tuner, but I used the external tuner so I could tune up the amp on a dummy load rather than on the air. Over the years I did occasionally forget to switch the tuner into or out of bypass when going to a different band. So, manual switching rather than manual tuning was a bit of a problem. Now used to the KPA500/KAT500, I am spoiled and don't want to go back to having to remember to switch. I was hoping that the KPA1500 would not have the tuner built in, but I can see how most users save money with a built-in tuner. When I said my antenna swr can be up to 4.5, I quoted the worst case I can remember. The 40m coil is copper clamped onto aluminum elements. When I installed the antenna in 1993 I didn't apply compound to keep the joints healthy. Over the years, when I have been inactive for a long period such as a year, I have noticed the higher swr values that I quoted. Some operation at high power has then restored band edge swr readings to somewhat lower values, such as 4:1. If I recall correctly, those readings were well under 4:1 when the antenna was newly installed. I intend to service the antenna some day and get back to those better swr readings, but accessing the antenna for service is for me a big and difficult undertaking. With the prospect of getting somewhat close to the 3:1 limit, I am very interested in detailed derating numbers for the KPA1500 tuner, as well as any information that might indicate that it can safely handle somewhat higher swr depending on the actual complex load impedance..
73, Erik K7TV -----Original Message----- From: elecraft-boun...@mailman.qth.net <elecraft-boun...@mailman.qth.net> On Behalf Of Ignacy Sent: Wednesday, October 17, 2018 7:59 AM To: elecraft@mailman.qth.net Subject: Re: [Elecraft] Looking at KPA1500 The low range tuners up to 3:1 are very low loss and then can be made reliable. High range tuner for 1.5KW would be less so. You may buy MFJ-998 as an extra. I use MFJ-998 with 1.5 KW and a ladderline-fed dipole for a few years. Only small problems like burnt diode in SWR circuit or smoked capacitor by the output connector. But it is better to have such problems outside of the amp. Another choice is to have an AB switch where the same antenna is connected to A directly and to B via capacitor that lowers the SWR where otherwise it is too high. Ignacy, NO9E ______________________________________________________________ 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
