I modified the L4 because I didn't want to fry my TS-870 keying circuit. I know how the unmodified L4 works, BTW.
I have already kludged a circuit in-line using a PNP transistor and a few resistors, picking up the +12V out of the K3 and the Key Out line and providing the necessary keyed 12V. This will have to do until I get around to my vacuum relay QSK/electronic bias switch mod for the L4. What a difference 10 dB makes. Life is too short for QRP. Wes N7WS --- On Sat, 9/5/09, Guy Olinger K2AV <[email protected]> wrote: From: Guy Olinger K2AV <[email protected]> Subject: Re: [Elecraft] [K3] Need +12V on TX To: "Wes Stewart" <[email protected]> Cc: [email protected] Date: Saturday, September 5, 2009, 7:35 PM It is getting quite rare for the transceiver to SUPPLY 12 volts to key an amp. All the currently manufactured amps require a GROUND to key an amp, the AMP supplies a voltage to be keyed, INCLUDING an unmodified L4B using the "VOX" lead, which is the equivalent of the more familiar "relay" lead on Ameritron and others. >From the schematic, the L4B would have expected a ground on the non-ground VOX lead to key the amp. Since from the schematic, this would have been a positive DC voltage less than 200 volts, the K3 should have keyed it fine as is. There is a caution about reversing the plug in the manual, which was not keyed in any particular way, and COULD have put a permanent key to the amp if reversed and the transceiver end was grounded in operation. Drake was expecting a relay in which the orientation would not matter. Why did you modify it? 73, Guy. On Sat, Sep 5, 2009 at 1:05 PM, Wes Stewart<[email protected]> wrote: > I added a solid-state relay driver in my old Drake L4-B that requires +12V > (or so) from the transceiver on transmit. My trusty TS-870 supplies this > signal. > > I'm getting tired of running QRP with the K3 and would like to be able to use > the amp with my K3 without further fuss. Is there a magic way to get this > signal from the K3 or am I going to be forced to mod the amp again, kluge > another circuit in-line, or forget the idea and stick with the '870? > > Wes N7WS > > > > > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[email protected] > > 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:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
