Hi Jim I bought a bunch of these for my station in 8P. When you reported your findings with these devices, I was very concerned. I had one in 8P with me at the time and I measured it in my AIM 4170. I could not reproduce your observations and used it on 10M with no obvious issues.
Since I have been home, I took another set of measurements with my DG8SAQ VNA. They were essentially identical to what I measured in 8P. Just so we are clear on definitions, I measured them in in both directions using both ports and a precision 50 ohm load. In-A had a steadily rising SWR with frequency, maxing out at 1.1:1 on 28Mhz. In-B was slightly worse with the same shape and a max SWR of 1.15:1 at 28 Mhz. It was the same in both directions and did not change if the unused port was terminated or open. The isolation was essentially as advertised, over 80 dB up to 28 Mhz. Admittedly 1.15:1 is not world class, and could be better, but I don't consider it unacceptable and I plan on using the switches I bought. Are we drawing different conclusions from the same data? If you had different measurements, I would be curious if there was some design change along the way. I did not open them up. The units I have were bought from another ham, but they were unused. They also make a product called an Op Swapper that has some other functionality. What I am testing is the A/B station selector. 73, Tom W2SC -----Original Message----- From: elecraft-boun...@mailman.qth.net <elecraft-boun...@mailman.qth.net> On Behalf Of Jim Brown Sent: Sunday, March 17, 2019 8:12 PM To: elecraft@mailman.qth.net Subject: Re: [Elecraft] Using Elecraft KPA-1500 for 2 radios Not a great choice. SWR gets increasing nasty above 15M because the construction uses chassis as signal return rather than carrying it on the circuit board. It's a two-sided board, but the "ground" layer is broken under the traces that carry the RF, so return current can't flow on that layer. I didn't have the heart to try to measure crosstalk. 5-6 years ago, I bought several of them for antenna switching, and learned that the hard way. I modified them by paralleling copper braid from the connectors to the board and following the RF paths through the relays across the board as best I could. That reduced the SWR by about half. I've since replaced all of them, and they're for sale. :) 73, Jim K9YC On 3/17/2019 6:15 PM, Bill Steffey wrote: > i use topten a/b coax switches,,,, to switch between the kpa500 & > acom 2000 ... one in front of the amps , one in back .... also > have them switching between K3 & an Icom.... > > https://toptendevices.com/products/ab-station-selector/ ______________________________________________________________ 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 ______________________________________________________________ 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
