[Elecraft] Simple way to set L34

[Ron D'Eau Claire]

Gary Surrency posted a message here a year or so ago about setting L4
using a DMM rather than by "ear". Of course I lost it, but the next time
I wanted to check the setting I recreated my own version of it (might
even be the same) by remembering is general approach.

The procedure is to tune the 7 MHz "birdie" and adjust L34 for maximum
AGC voltage. Since the AGC voltage is a function of the amount of signal
coming out of the IF amplifier, that assures you that L34 is on its
"peak". 

I connect the DMM to the "hot" end of R2 on the Control Board. The
Control board is the one attached to the front panel assembly that faces
toward the inside of the K2. Looking down onto the board from the top
with the cover removed, R2 is right next to U2 on the right end of the
board near the top edge. The end of R2 nearest the top of the board is
grounded. You must connect  the test probe to the end of R2 furthest
from the top edge of the board. Be sure you don't short to the adjacent
component leads. 

Connect a dummy load to the rig. You must avoid picking up any outside
signals or noise. They will mask the reading. 

Turn the K2 On.

Turn the preamp On. 

Ensure the AGC is On

Set RF Gain at maximum (fully clockwise).

Tune in the 7 MHz "birdie". Use SPOT to be sure that you have it right
on frequency. 

Now adjust L34 for MINIMUM voltage on the DMM. The setting is a bit
broad, but I find a very definite "peak" indicated minimum voltage at
one spot in the L34 adjustment.

A DMM is required because the change in voltage is only a few hundredths
of a volt with a little over 3 volts to ground.  In mine the voltage
sits at about 3.646 on the "sweet spot" rising to 3.647 or 3.648 1/8 to
1/4 turn off of the "peak" in either direction. 

That does it for me. 

Ron AC7AC
K2 # 1289

===============================================
 no9e wrote:
>2. After doing 2nd XTAL mod, the sensitivity with FL2-4 is about 10 db
>lower than with F1. Also, I feel that the CW sensitivity is lower. I 
>peaked L34 but the peak was not too sharp. Does the modification
(inluding 
>removal of 10p), deteriorate CW sensitivity? I used BC337 instead of
PN2222.

kevin wrote:
Finding the point of maximum signal with least noise is not an easy
thing 
to do by ear alone. There is no sharp peak as you have found. I have a 
procedure for setting L34 using Spectogram but I haven't written it up
yet. 
Its on my list of things to be done however. Hopefully soon.