K2 Rec Low Audio Output and AGC Adj

[W7is]

I've noticed a larger number of posts regarding low audio output with  the
K2.    
I'm sure there are various reasons for low audio.   Such as  wiring the
speakers
 wrong etc..    Poor soldering etc.  
I have two K2's and both of them had to be hooked up to external
amplified speakers in order to provide a comfortable room listening volume.
Especially when the signal levels on the bands were very low.
 
Per page 47 of the assembly manual,  you set the AGC threshold by  reading
the voltage
on Pin 5 of U2 and adj R1 for 3.8V (suggested setting that will be adjusted  
later
to suit the operator).    But there is nothing in the  manual to indicate
what AGC
setting is best.  Then I decided to search this forum regarding  adjusting
the AGC.
Others were setting the AGC threshold by listening on a quite band and  while
turning
the AGC on and off,  adjust R1 for no difference in the received audio  
level.    
Turning the AGC on and off by holding down Pre/ATT and AGC simulaneously.
Or you can use a program like Ham Radio Deluxe that provideds a  single
button to turn AGC on an off via software commands.   After  your done
setting the
AGC threshold, its necessary to  re-adjust the S meter alignment.
 
Others have said to hook your rig to a dummy load while adjusting the AGC  in
this way.   I completed the AGC adjustments when  20M had a very low noise
level
during the evening hours.    Now I have more than enough  room filling vol
without
needing amp spkr's and typically run the audio around the 10 O'clock  
position.  
Others go to great lengths to say to adjust it with the Pre-amp  off etc ....
 
Since I never turn the Pre-amp off and I run the RF gain control at max at  
all times,
 its a non issue for me.....  
 
I'm sure each person has there own particular operating requirements.   And
have their
own way to adjust the AGC that suits them.     The way  I did it, I cant be
happier
with the performance the K2 now.  Room filling volumn using the  internal
speaker
and the AGC still does the job on strong signals in a way that I'm happy  
with.  
 
Frank W7is  
 
 
 
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[Don Wilhelm-3]

Frank and all,

Well, I have been responsible for a number of posts on adjusting the AGC
threshold.  I have found that each K2 is a little different, and one of the
dependencies on the proper AGC threshold level is the actual voltage out of
the 8 volt regulator, but I have not been able to come up with a clear and
easy 'formula' to determine the proper AGC Threshold voltage setting - the
best way is to 'do it by ear' - that says there are more things than just
the 8 volt regulator voltage which affects the proper level.

I will say that the AGC Threshold should be set somewhere between 3.7 and
3.8 volts,  or if you have a desire to set it lower, consider 3.65 volts as
an absolute minimum.  If the Threshold is set too low, the S-meter will
become difficult to set and you may not be able to obtain an S-9 indication
with a 50 microvolt input (XG1 or XG3 output level).

I do recommend evaluating the AGC on/AGC off difference with no antenna, on
40 meters, and with the preamp off - but the choice is yours on those
parameters, if you want to adjust it for a different set of conditions, you
will obtain different results, but it will still work, there is no real
'right and wrong' set of conditions, it is really a matter of choice (as
long as you are willing to accept the performance that results from your
choice).

The RF Gain control works in the same circuit as the AGC Threshold, so if
you have a high noise level, you can always back off on the RF Gain to
reduce the threshold temporaily and keep the noise (or a strong signal) from
activating the AGC - the consequence is that the S-meter will not read as it
was calibrated with the RF Gain reduced, but under extreme conditions, that
is a small matter IMHO.

73,
Don W3FPR

> -----Original Message-----
>
> Others have said to hook your rig to a dummy load while adjusting
> the AGC  in
> this way.   I completed the AGC adjustments when  20M had a very
> low noise
> level
> during the evening hours.    Now I have more than enough  room
> filling vol
> without
> needing amp spkr's and typically run the audio around the 10 O'clock
> position.
> Others go to great lengths to say to adjust it with the Pre-amp
> off etc ....
>
>

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