[Elecraft] [K2] AGC Time Constant

[Don Wilhelm]

Al,

The dynamic balance between the base and emitter of Q12 determine the 
AGC Fast/Slow response.  The dynamic characteristics of Q12 as well as 
R2, C4, RP6 and C1 all come into play.
Remember when doing the analysis that the voltage at /SLOW AGC is at 5 
volts for fast AGC.  When you consider the dynamic response, C1/RP6 pins 
1-2 are important.  From a dynamic relationship, that biases the emitter 
of Q12 to something near 5 volts and obliterates the effect of the R2/C4 
time constant.

73,
Don W3FPR

On 7/15/2016 12:11 AM, Al Lorona wrote:
> I'm looking at the K2 schematic at the components on the Control Board that set the AGC time constant, and I can't understand how the fast setting gets its time constant... the parts involved, C4 and R2, appear to have a very long time, much longer than necessary for the FST settting.
>
> If you know what's going on could you contact me off-list to explain it to me? Thanks.
> R,
> Al  W6LX
>
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