[Elecraft] Re: AGC adjustment

[Wayne Burdick]

David Gropper wrote:
> 
> Wayne, Earl,
> 
> I would sure appreciate a short email explaining what to do!


Hi Dave,

In practice, the setting of the AGC threshold pot is a compromise. Setting it to
a higher voltage results in the AGC coming on sooner, i.e. with lower-amplitude
on-air signals. Setting it to lower voltages prevents the AGC from reducing the
audio output level of the K2.

The 3.8 volt setting, which is the one recommended in the K2 manual (revision E,
page 46), is a good choice for most operators. As the manual explains, you can
optimize this setting later if desired.

The approach I take is:

1. With an antenna connected, switch to a "quiet" band (one with light
atmospheric background noise, e.g. 15 m at night). Tune to a place with no
incoming signal. 

2. Turn AGC OFF (using PRE/AGC + AGC as explained on page 97 of the manual). If
the background noise level increases dramatically with AGC off, the AGC
threshold is probably set too aggressively. A lower voltage setting, as measured
at pin 5 of U2 on the Control board, might be more appropriate. I'd try 3.5 or
3.6 V for starters. (Note: when adjusting the AGC threshold, disconnect the
antenna. Otherwise incoming signals could make it harder to adjust.)

3. After selecting a different threshold setting, test the AGC on strong signals
to make sure you haven't set the threshold voltage too low.

4. Finally, adjust CAL S HI and CAL S LO as explained on page 46.

73,
Wayne