Fernando, Yes, I would say that 3.37 volts is a bit too low, and yes it will make a difference in how the RF Gain responds - both the RF Gain control and the AGC adjustment pot are in the same resistive network (no active devices involved) - it is a 2 legged resistor network with the RF Gain in one leg and the AGC Threshold pot in the other leg.
If you did AGC on/off evaluation with an antenna attached, you have set the AGC to not activate on band noise - the proper setting should be to set it so no AGC action occurs with internal receiver noise, so do it with the antenna disconnected - or if you want to be particular, with a dummy load attached. My guess is that you will end up with a voltage on U2 pin 5 of somewhere between 3.6 and 3.75 volts - at least that has been my experience. 3.8 volts is usually too high but a lot depends on the actual gain of the IF amplifier chip. If you end up with something as low as 3.37 volts using internal receiver noise only, you should investigate to see what is causing the excessive receiver noise. 73, Don W3FPR > -----Original Message----- > > 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? > > -- No virus found in this outgoing message. Checked by AVG Anti-Virus. Version: 7.0.323 / Virus Database: 267.6.6 - Release Date: 6/8/2005 _______________________________________________ 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
