[Elecraft] VCO Alignment on K2

[Don Wilhelm]

Jay,

I assume you are rferring to the voltage measured at the left end of R30
while the K2 is tuned to 4000 kHz - if the voltage does not decrease as you
tune lower in the band, then let's start again because you have a greater
problem than just a bit too much inductance or capacity.

First thing to do is look at the schematic for the RF Board sheet 1 of 4,
and identify the components shown in the area labeled VFO Range Selection.
Check those components for the proper values, especially be certain the
varactors are the correct type (the 1SV149 has a smaller body than the
MV209) and oare correctly oriented.  Also check varactors D23, D24, D25 and
D26).

Do count the turns on T5 once again, being certain that you are counting the
number of times the wire passes through the center of the core rather than
counting around the outside.  If the number of turns are correct, spread the
turns out (loosen the mounting hardware first) a bit and the voltage should
go down - you did spread the turns out over 85% of the core like shown in
the manual did you not?

Actually, it is usually preferrable to set the voltage when tuned to 4000
kHz a bit higher than 6 volts, in fact, I usually try for about 6.5 volts
there as long as all the other band end points are well within the
acceptable range.

73,
Don W3FPR


> -----Original Message-----
>
> Hello, I am to the point in my construction where I align the VCO.
> Every measurement has been correct to this point.  Unfortunately, the
> lowest voltage I can get on R30 is 6.1 volts.  I have checked that L30
> and C72 are both correct.
>
> It says that T5 is incorrectly wound in the manual.  It looks to me
> that both windings have the proper number of turns.  Does anyone have
> any hints on getting this voltage a little lower?
>
> Thanks & 73
> Jay
> KA9OKT
>