Sunday, November 13, 2016

AGC for the BITX

Many BITXers have longed for a simple AGC circuit. So here it is, it just fits all around the volume control. Here is the circuit :

The Audio-In from the original volume control comes into the circuit on the left and the Audio Out is sent to the volume control's hot end. The 2N7000 and the drain resistor together form a volume control. The tapped down audio is amplified by the transistor (use any NPN transistor) and rectified into a DC voltage by the diode. As the incoming audio level increases, the bias on the 2N7000 goes up and the drain-source resistance drops, bringing the volume down. Below is my ugly version of this AGC. I built it in a few minutes. For the last few hours, it has been fun using it.

5 comments:

  1. ¡Thanks Peter. Very good thing! Regards. LU1AR

    ReplyDelete
  2. This comment has been removed by the author.

    ReplyDelete
  3. the AGC action can be improved by replacing the 100k resistor connected to the anode of the diode with another diode. Cathode of new diode connects to the anode of the existing one

    ReplyDelete
  4. This comment has been removed by the author.

    ReplyDelete
  5. I need a circuit that uses only npn transistors, as I have no FETs other than a few IRF510's, and those I got to possibly make an amp, and replace the PA if needed.

    ReplyDelete