[Elecraft] AGC Threshold voltage?

[W3FPR - Don Wilhelm]

Tim,

Actually that troubleshooting section of the manual is incorrect - the gain
of the receiver will increase if you DECREASE the AGC THRESHOLD voltage.
The really optimized voltage for the AGC Threshold is the highest voltage
that shows no change in internal noise (no antenna connected) when changing
from AGC On to AGC Off (press AGC and PRE/ATT buttons together to toggle AGC
on/off).

I normally find that a setting in the range of 3.7 to 3.8 volts will be the
optimum point, but it will vary from K2 to K2.

Try monitoring the voltage at Control Board U2 pin 5 to convince yourself
that a lower voltage will result in higher gain.

The max voltage that one can find at U2 pin 5 will be determined by the
actual voltage on the 8A line - it will be a bit less than half that
voltage - and is not really an indication of any problem.  The 8A voltage
can vary from 7.6 volts to 8.4 volts and the regulator will still be in spec
(and OK for use in the K2).

73,
Don W3FPR

> -----Original Message-----

>
> The overall receiver gain  of the K2 I just built (serial number
> 4993) seems
> low as compared with my older serial number 315 K2.
>
> The max AGC threshold voltage I can get is 3.82 volts. (3.8 is what is
> called for in alignment and Test Part I), but the troubleshooting section
> says you can increase the voltage to increase the overall
> no-signal IF gain
> and that a typical setting might be 3.9 volts.  Mine is maxed out
> at 3.8...
> does this sound correct?
>
> Thanks
> Tim
> Nz8J
>
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