Fernanco, N2FQ wrote: Awhile back there was some mail about the AGC Mod on the K2. Specifically, adjusting R1 on the Control board.
My K2 had a fixed resistor so I replaced it with a 20 turn 50k one. I also followed the write up about how to adjust it for apparent equal noise with AGC ON/OFF. Worked like a charm and the final voltage on U2 pin 5 turn out to be 3.37vdc. The audio coming out the speaker booms now, BUT the RF control is not as effective as it used to be. Namely, I like to turn down the RF to lessen the background noise. Now I can turn the RF all the way ccw and see no apparent reduction in background noise. So I'm going back into the rig and play with it. My question is this: Did I make a too aggressive change on R1? ---------------------------------------------- Definitely yes! You've disabled the AGC. The RF GAIN is merely a manual AGC voltage controller. It does with a knob what the AGC amplifiers do automatically based on the received signal strength. Clearly, the RF GAIN no longer has sufficient voltage swing to turn down the I.F. amplifier gain. Another way to demonstrate that the AGC isn't working is to tune in a decently-strong signal, then turn the AGC off (press PRE/ATT and AGC buttons simultaneously. "OFF" will appear on the LCD display). If the AGC is working, you'll hear a huge increase in the signal level when you turn it off. If the signal stays the about same, the AGC is already off. Press the buttons again to see "On" appear on the LCD and you should hear the signal level drop as the AGC takes hold. Also the S-meter bar graph will indicate a signal strength. When the AGC is on, you want it to start reacting to the background noise just slightly. Of course that will vary from band to band. Most Hams live with the most QRN on 160 or 80 meters. Also turning the PREAMP on will increase the background noise. Ron AC7AC _______________________________________________ Elecraft mailing list Post to: [email protected] 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
