I'm planning to add an external amplifier/transverter keying circuit to one of my K2s. I found two versions on the web, both apparently designed by N0SS (SK). The one on the Elecraft site (http://www.elecraft.com/Apps/Amp_keying_ckt.htm ) appears to be his original circuit, using a 2N7000 driving a 2N2222. The archive of Tom's later kit offering (http://www.mmccs.com/mmarc/n0ss/k2_t-r_rly_drvr.pdf ) uses two MOSFETs and is capable of keying somewhat higher voltage and current. But also he added a 100k resistor from the input gate (8R) to ground and another from the gate of the second MOSFET to ground. I am trying to figure out if these two 100 k resistors serve any useful purpose or if I can happily leave them both out of the 2-MOSFET circuit. There doesn't immediately appear to be any need to pull these gates down as there are several loads on the input 8R voltage (on the K2 RF board) which will do that for the 1st MOSFET, and the 1st MOSFET will pull down the gate of the 2nd one when needed. Maybe something odd will happen on power-up or power-down? Any thoughts? 73,Steve VE3SMA ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net
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