"de-sensitizing" C22

[Vern Kollas]

Good morning to all....

First of all my K2 (base CW) is finally complete and
has passed all of the basic tests with flying colors.
Now that I can receive on all bands, I decided to go
back and do a more thorough calibration of the 4MHz
reference clock and then start on the filters before
moving on to build the SSB module and the 100W amp.
After reading through some of the reflector archives,
checking some of other resources on the Elecraft site
and passing some emails back and forth with Tom, N0SS,
I finally got a good understanding of how the
calibration works and what needed to be done.  I am
able to get pretty close, in fact I had it within 50Hz
to start with, and at one point had it at about 23Hz
off.  However, that is about as good as I have been
able to get it. Once I get to a certain point, just
breathing seems to move the frequency when adjusting
C22.  I know I am really close, but I would love to
see if I can really get it closer.  So my question for
the group here is there any way to make C22 not so
sensitive to even just touching it with an alignment
tool??  I have read where some have added a cap in
parallel with C22 to "extend" the range, but would
this also help it to not be so touchy to adjust??  Or
should I just look to replace C22 entirely with a
different cap??

I know I shouldn't be quite so picky, but hey, that is
the fun of building the radio.  You can tweak things
and make it do what you need/want it to do.  I also
must say that I am REALLY impressed with this radio so
far.  It does receive very well, and the filters seem
to be working VERY well with just the default
alignment.  I am really getting excited to see how
well it will work once I get Spectrogram and "do it
right".

Anyway, thanks for letting me ramble on here and
thanks in advance for the help!!

73!

Vern -- KC8YOH  

__________________________________________________
Do You Yahoo!?
Tired of spam?  Yahoo! Mail has the best spam protection around
http://mail.yahoo.com 
_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
 http://mailman.qth.net/mailman/listinfo/elecraft   

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com

[Don Wilhelm-3]

Vern,

Use a long slender metal screwdriver that nicely fits into the cap slot and
you will find it much easier to adjust.  If you are using the alignment tool
supplied with the K2, it is too flexible for precise adjustment.  If you
mounted C22 the right way 'round, the adjustment slot should be grounded, so
you can use a metallic screwdriver without changing the capacitance.

I must admit that it is still a bit 'touchy', but it is much less so with a
solid tool.

I believe it was John Grebenkemper KI6WX who wrote something up on changing
the range of C22 a while back - it should take a  smaller capacitor in
series with the trimmer (change C21) as well as adding a cap in parallel
with the trimmer to get the total capacitance value back where it should be.
It might be on the LA3ZA mod list.
http://www.qslnet.de/member/la3za/K2/mod.html , but you could experiment
with the values to get the trimmer range that you want.

73,
Don W3FPR

> -----Original Message-----
>
> First of all my K2 (base CW) is finally complete and
> has passed all of the basic tests with flying colors.
> Now that I can receive on all bands, I decided to go
> back and do a more thorough calibration of the 4MHz
> reference clock and then start on the filters before
> moving on to build the SSB module and the 100W amp.
> After reading through some of the reflector archives,
> checking some of other resources on the Elecraft site
> and passing some emails back and forth with Tom, N0SS,
> I finally got a good understanding of how the
> calibration works and what needed to be done.  I am
> able to get pretty close, in fact I had it within 50Hz
> to start with, and at one point had it at about 23Hz
> off.  However, that is about as good as I have been
> able to get it. Once I get to a certain point, just
> breathing seems to move the frequency when adjusting
> C22.  I know I am really close, but I would love to
> see if I can really get it closer.  So my question for
> the group here is there any way to make C22 not so
> sensitive to even just touching it with an alignment
> tool??  I have read where some have added a cap in
> parallel with C22 to "extend" the range, but would
> this also help it to not be so touchy to adjust??  Or
> should I just look to replace C22 entirely with a
> different cap??
>
> I know I shouldn't be quite so picky, but hey, that is
> the fun of building the radio.  You can tweak things
> and make it do what you need/want it to do.  I also
> must say that I am REALLY impressed with this radio so
> far.  It does receive very well, and the filters seem
> to be working VERY well with just the default
> alignment.  I am really getting excited to see how
> well it will work once I get Spectrogram and "do it
> right".
>
> Anyway, thanks for letting me ramble on here and
> thanks in advance for the help!!
>
> 73!
>
> Vern -- KC8YOH
>

_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
 http://mailman.qth.net/mailman/listinfo/elecraft   

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com