For folks not wanting to modify their amps, a solid-state amp buffer can be placed between the K3 and TL-922. I like the Jackson Harbor "Keyall" circuit since it can switch up to 500V AC/DC at several amps and it optically isolates the K3's switching transistor from the amp.
http://wb9kzy.com/keyall.pdf The Keyall is sold as a kit through Jackson Harbor Press, although Andy, W8CNZ is providing an assembled plug-'n-play device for about USD $25. Paul, W9AC ----- Original Message ----- From: "Joe Subich, W4TV" <li...@subich.com> To: <elecraft@mailman.qth.net> Sent: Friday, September 02, 2011 9:38 PM Subject: Re: [Elecraft] K3 with a Kenwood TL-922A > > > > Anything I need to know before I hook the K3 up to it. > > Don't do it! The TL-922 has a high voltage PTT line with *no* current > limiting and no reverse EMF diode across the relay coils. The relay > current is rather high and the "spike" when releasing PTT is quite > high. You will need to add a Harbach engineering "soft key" board - > www.harbachelectronics.com/main/page_products_kenwood_tl922a.html - > in order to keep from blowing the K3's keying FET and potentially > causing other damage to the K3 due to the spike. > > Even if you add the soft key board, I would recommend adding "back > diodes" across the T/R relay coils and adding a series resistor in > the relay line to keep the current down and minimize the potential > for a spike. > > 73, > > ... Joe, W4TV > > > On 9/2/2011 8:57 PM, Chris Hembree wrote: >> I am buying a Kenwood TL-922A Amp. Anything I need to know before I hook >> the K3 up to it. >> >> Thanks >> Chris W7CTH >> ______________________________________________________________ >> 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 ______________________________________________________________ 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
