Ron and all, For anyone contemplating connecting an analog S-meter to the K2, A better connection point for the takeoff AGC voltage is Control Board U2 pin 1. That point should have a voltage relating to the signal strength whereas the AGC input into the MC1350 is a current based rather than voltage - the only difference between the two points is a resistor (R4), but still using U2 pin 1 will not have potentila adverse effects on the normal K2 AGC operation.
I don't know what the voltage swing relative to S-meter readings are (that calculation is currently done inside the firmware), but those interested can experiment a bit. An op amp or two should be able to scale whatever AGC voltage is developed at U2 pin 1 to whatever your meter wants. 73, Don W3FPR > -----Original Message----- > ... snip > The K2 uses an MC1350 I.C. It has a maximum gain control range of > perhaps 60 > dB. Now, in rigs like the K2 with their excellent dynamic range that's > enough when it's coupled with manual control of the front end gain but, as > you noticed, it's not enough to silence the receiver when it's turned all > the way down, particularly if you have the preamplifier switched on. > > I agree with your lusting for a real meter on the K2! I've > considered doing > exactly that many times. It should be straightforward to do. The > MC1350 uses > an analog d-c voltage to control its gain. The voltage runs, > typically, from > +5 to +7 vdc to vary the gain of the MC1350 over its range. That > voltage is > applied to pin 5 of the I.C. > ... snip > _______________________________________________ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
