[Elecraft] K2 - setting the AGC threshold

[Don Wilhelm]

Johnny,

All will be OK if you just set it to maximum.
The cause is the 8 volt regulator is on the low end of its tolerance range.
You could replace the regulator to being it up, but you will not notice
any difference in the K2 nor its performance.
If you wish to increase the AGC Threshold voltage without changing the
regulator, you can solder a resistor across pins 3 and 4 of RP6 - you
may have to experiment a bit with the value until you can obtain a bit
greater than 3.8 volts from the AGC Threshold pot adjustment, I would
recommend starting with 15k and work from there.

Be aware that there is a note in the manual instructions for Setting the
AGC Threshold which states that "This is the suggested setting, but it
can be adjusted later to suit the operator". Any setting that will
improve the sensitivity of the K2 will be lower than 3.8 volts. If the
AGC Threshold is set too low (below 3.65 volts or so), the S-meter
adjustments get a bit tedious if one is picky about the low end reading,
the high end reading and the S-9 reading with a 50 uV input signal. All
3 conditions can usually only be met with an AGC Threshold voltage in
the 3.7 to 3.8 volt range.

73,
Don W3FPR

Johnny Siu wrote:
> Hello Group,
>
> Although I built a lot of K2 in the past, I encountered problem nearly each time.  This time, p.48 of the K2 manual, I can only get a maximum voltage of 3.75v no matter how I adjust R1 on the control board.
>
> Is this matter? If yes, how I can solve the problem and get a reading of 3.8v on DMM.
>
>