Now let me answer my own question. There is a key-line interrupter adapter that I believe comes with the AUXIO cable. This is an HD-15 type adapter that will block the PTT signal from the K3 to the AUXIO cable. Use this, then you will need to connect the K3 to the KAT500/KPA500 using a phono cable. You will probably want to add a switch so that you can select the K3 or Icom radios for the PTT line to the KPA/KAT.
Once again, Fred Cady had the answer in his “Elecraft KPA500 Amplifier and KAT500 Tuner” guide. I really miss that guy… 73, Jack W6FB > On Mar 31, 2022, at 11:47 PM, Jack Brindle via Elecraft > <elecraft@mailman.qth.net> wrote: > > OK, now this is starting to make sense. Jim’s K3 has a KIO3, not the newer > KIO3B. On the older board, the BAND and PTT lines have pullup resistors to > the Vcc rail. > When the K3 is powered off, that Vcc rail is at 0 volts, which means the > pull-ups are now pulldowns. Thus the K3 is inadvertently keying the KPA500. > If the KPA > detects that the KEY input is low when the user tries to put it into OPER > mode, the amplifier will reject the request and stay in STBY. Thus the > condition that > Jim is seeing. > > Try disconnecting the AUXIO cable from the KPA500 and see if it now operates > properly. You may actually need to connect the KAT500 to the KPA using both > the AuxIO > and phono cables (for PTT) depending on which radio is in use. > > The main issue is how to disconnect the PTT signal from the K3 to the KPA > when using the Icom. Otherwise you may be able to leave the AuxIO cable > connected. > I know that Fred Cady discussed sharing a KPA between two radios in his book, > but has anyone solved this situation - one radio is a K3, the other something > else? > > 73, > Jack, W6FB > >> On Mar 31, 2022, at 9:11 PM, James Bennett via Elecraft >> <elecraft@mailman.qth.net> wrote: >> >> Bob - >> >> The * appears when I key the K3 and the amp is in operate mode. Likewise if >> I key the 705 and the amp is in operate mode, with the K3 powered on. >> >> If I power off the K3 and place the amp in operate mode WITHOUT KEYING IT, >> the * appears, so you are correct - the amp thinks it is being keyed. >> >> There is a jack on the 705 that allows one to key an external amp. I have >> that line running to the amp. Disconnecting it makes no difference the * >> appears as soon as I put the amp into operate mode. If I power on the K3, >> this does not happen. However, with the K3 powered on and that cable >> disconnected, the amp does not key at all, so it is working as expected - >> but only with the K3 powered on. Somewhere the K3 is getting its foot in the >> door when powered off… >> >> Jim / K7TXA >> >> p.s. do you have any idea what Jack was talking about when he said "switch >> the RADIO setting of the KPA from K3 to something else, either Serial or >> Analog”?? >> ______________________________________________________________ >> 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 jackbrin...@me.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 jackbrin...@me.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
