[Elecraft] K2 Problem Aligning IF Amplifier

[Don Wilhelm]

Michael,

Likely not a problem at all - it sounds like things are within the realm of
normalcy.

The peak on L34 is VERY broad - and that usually means that it is not
super-critical.  The proper setting is for the best signal to noise ratio,
and that can vary from the actual peak.  For the time being, set the slug in
about 1 turn down from the top of the can and everything should work just
fine.  The proper setting is often difficult to discern by ear.

When you have the K2 all completed, you will likely want to optimize your IF
filter settings with Spectrogram or a similar program running on your
computer soundcard.  When you are set up for such a spectral display, you
can easily 'fine tune' the L34 setting easily by observing the lowest level
of the noise floor that is consistent with the highest amplitude of the 7000
kHz birdie.  I use a CW filter width of about 700 Hz when fine-tuning L34
because it gives me the easiest results.

If you want to set the filters and optimize the L34 slug with Spectrogram
now, you can do that since you have a fully functional 40 meter receiver.
These settings will not be affected by the assembly steps that follow.
OTOH, most folks will install the KSB2 - and if that is in your plan, I
suggest that you wait until you have that SSB option installed before doing
your filter alignment so you can include the OP1 SSB filter in your filter
alignment procedure.

73,
Don W3FPR

> -----Original Message-----
>
> I'm having a slight problem aligning the I.F. amplifier.
>
> The instructions indicate that the 7000 kHz signal will yield best signal
> strength and lowest noise at about 1 to 1.5 turns below the top
> of the can.
> However, the best 7000 khz signal strength and lowest noise occur when I
> tune the slug of L34 at the top of the can.  It also appears as
> if greater
> signal strength could be obtained if I could tune the slug
> furhter out, but
> I cannot do this because the slug is already tuned at the top of
> the can.
> This implies to me that there may be something wrong in the IF
> circuit since
> I do not find the peak of the signal about 1 to 1.5 turns from the top of
> the can.
>
> I examined the circuit diagram in Appendix B and found L34.
> Capacitor C182
> (180 pf) is connected to L34.  I verified that the correct capacitor is
> being used for C182.
>
> I also did the 40 meter bandpass filter alignment by adjusting L1
> and L2.
> All the other alignments in Part II of the Alignment and Test
> section have
> been successfully completed, including the VCO alignment, BFO
> Alignment and
> VFO Linearization.
>
> When connected to an antenna, the 40 meter receiver seems to work pretty
> well.  I can successfully receive CW and SSB.
>
> I'm stumped about the I.F. alignment problem and believe that I should be
> able to find the peak of the signal about one turn or more into
> L34 instead
> of at the very top of the can.
>
> Does anyone have any suggestions as to what I should do or check
> in order to
> correct this problem?
>
> 73 de KI5E  Michael
>