> You might have a problem when only one rig is powered up, with the > unpowered one pulling down the key/control line. The K3 is OK, as both > outputs are open drain/collector. If that's also the case with the ICOM, > the "Y" connector should work. If the ICOM has a pull-up resistor, or > anything except an open drain/collector connected to that control line, > there could be a problem...
In that case, a Schottky steering diode can be used on the Icom key line. A 1N914 or 1N400X series may be fine but I've seen instances where the higher diode junction voltage prevents the line from going low enough to circuit ground potential. Not sure how sensitive the Alpha 9500 is to that effect. I agree with Scott that the K3 should be fine with its open-drain on the MOSFET switch. I don't see this issue very often on the amp key line -- I do see it often when trying to use a single CW keyer, feeding multiple transceiver's in parallel, due to the use of pull-up resistors on the paddle key line. Again, Schottky steering diodes used for isolation at the input to each transceiver's CW key line solves the problem. Paul, W9AC ______________________________________________________________ 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
