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Another twist to AGC for the ubitx


barry halterman
 

Fellow ubitx tinkers. I found this partial circuit in the book, Experimental methods in RF design. It is a double peak detector that gives a smoother AGC response rather then a single diode detector. I have done some work with it and like the response so far. I have attached my drawing of the circuit if anyone wants to test it out. I am using a PIN diode off of the emitter follower Q32. My diode of preference is the 1N5767, but I have used 1N4005, 4007 and MPN3404 diodes with similar response. One thing with this circuit is that is does not load down the audio. With the audio being taken off the high side of the volume control, I built up a small pcb that I can plug right in to the audio connector on the front of the v6 board. Of course since it is detecting audio, there will be that KW down the street that still will blast through, but for the most part it works very well.
Barry
K3bo


barry halterman
 

Forgot to add the schematic.


Evan Hand
 

Barry,
Did you mean to include a schematic?  I did not see any files in the email.

Your description sounds like one that is available from AmateurRadioKits.  
73
Evan
AC9TU


Evan Hand
 

Barry,
Our emails passed each other.  I see the schematic and it is NOT like the one from AmateturRadioKits.  I have another uBITX that does not yet have AGC.  It will take a while until I gather the parts and get the time to make the mod.  I will report back when I get it done.

Thank you for the design.
73
Evan
AC9TU


barry halterman
 

Evan, yeh, I hit send then realized I had not attached the diagram...
Barry


On Sun, Oct 11, 2020, 5:01 PM Evan Hand <elhandjr@...> wrote:
Barry,
Our emails passed each other.  I see the schematic and it is NOT like the one from AmateturRadioKits.  I have another uBITX that does not yet have AGC.  It will take a while until I gather the parts and get the time to make the mod.  I will report back when I get it done.

Thank you for the design.
73
Evan
AC9TU


Trystan G0KAY
 

Barry,

You have done an exceptionally tidy job of drawing out that schematic.

Trystan


On Sun, Oct 11, 2020 at 10:52 PM, barry halterman wrote:
Evan, yeh, I hit send then realized I had not attached the diagram...
Barry
 

On Sun, Oct 11, 2020, 5:01 PM Evan Hand <elhandjr@...> wrote:
Barry,
Our emails passed each other.  I see the schematic and it is NOT like the one from AmateturRadioKits.  I have another uBITX that does not yet have AGC.  It will take a while until I gather the parts and get the time to make the mod.  I will report back when I get it done.

Thank you for the design.
73
Evan
AC9TU


Ashhar Farhan
 

how much of AGC range are you getting out of the emitter degeneration arrangement? A different approach maybe to use a series diode. 
- f

On Mon, Oct 12, 2020 at 1:45 PM Trystan G0KAY <trystandavies+nodirect@...> wrote:
Barry,

You have done an exceptionally tidy job of drawing out that schematic.

Trystan

On Sun, Oct 11, 2020 at 10:52 PM, barry halterman wrote:
Evan, yeh, I hit send then realized I had not attached the diagram...
Barry
 

On Sun, Oct 11, 2020, 5:01 PM Evan Hand <elhandjr@...> wrote:
Barry,
Our emails passed each other.  I see the schematic and it is NOT like the one from AmateturRadioKits.  I have another uBITX that does not yet have AGC.  It will take a while until I gather the parts and get the time to make the mod.  I will report back when I get it done.

Thank you for the design.
73
Evan
AC9TU


Mitchel Rought
 

on the print I have for the V6, R37 and C32 from Q32 are reversed, typo ?


barry halterman
 

The voltage off the emitter ranges from zero to about 7volts.


On Mon, Oct 12, 2020, 2:29 PM Mitchel Rought <mitchelrought@...> wrote:
on the print I have for the V6, R37 and C32 from Q32 are reversed, typo ?


barry halterman
 

Mitchel, you are correct the schematic shows the cap then the resistors but on the board it is resistor then cap.
Barry

On Mon, Oct 12, 2020, 5:53 PM barry halterman via groups.io <kthreebo=gmail.com@groups.io> wrote:
The voltage off the emitter ranges from zero to about 7volts.


On Mon, Oct 12, 2020, 2:29 PM Mitchel Rought <mitchelrought@...> wrote:
on the print I have for the V6, R37 and C32 from Q32 are reversed, typo ?