I have used this method on 3 or 4 of the K2's I have built. I use a 1pF or
2pF NPO cap to lower the bottom end of the range to get it to meet the spec.
I agree with you on pulling the crystal much with this method. I would not
recommend cap values above maybe 3 or 4 pF. I have never needed more than 1
pf. Padding C173 and C174 is a better method if the radio needs more than 1
or 2 pf. I believe this method was suggested by Gary at Elecraft some time
back. At any rate it is a little easier to do than the padding or change out
> Sverre,
>
> I have not tried that small capacitor from the junction of the crystals
> and
> L33 so I cannot comment on it from that standpoint.
>
> What I would like to state is that when one pulls a crystal by any method,
> the stability becomes worse as the amount of pulling becomes greater. One
> should be aware of this and related facts when modifying any circuit in a
> way that is not 'approved and tested'. Also due to the nature of
> crystals,
> something that happens to work in one situation may not work the same for
> all cases. Remember that I am only bringing up cautions here, I am not
> makeing a firm statement about the operation one way or another.
>
> It certainly would be nice if someone (or better yet, several someones)
> with
> access to suitable instrumentation could try this or any other mod and
> report the results. The fact that it worked on a sample of one does not
> create a statement that it will work in other cases - that is simple
> statistical knowledge - I would like to see something that says it works
> in
> at least 5 or 10 trials before drawing any firm conclusions.
>
> So, yes I think it should be left on your website, but you may want to put
> a
> "Use at your own peril" disclaimer on all those that are not 'approved by
> Elecraft' or otherwise adequately tested (and I invite you to add any of
> my
> mods to that group as well, even though I have absolute confidence in my
> own
> work).
>
> 73,
> Don W3FPR
>
> > -----Original Message-----
> > >
> > > The preferred method of padding the BFO capacitors is to
> > > maintain the ratio between C173 and C174 by paralleling them
> > > with capacitors. A single capacitor from the junction to
> > > ground will be in parallel with the series combination of
> > > C173 and the varactor D38 and could make the BFO less stable
> > > than it should be.
> > >
> >
> > Don,
> >
> > How about a single capacitor (1-4 pF) from the junction of the
> > crystals and
> > the L33 inductor as in
> >
http://www.ac6rm.net/mailarchive/html/elecraft-list/2005-08/msg00562.html?
> > Does that create potential stability problems also?
> >
> > I've got this link on my K2 mods page and just wanted to make sure I can
> > recommend it and keep it there. I have never had any problems
> > with BFO range
> > myself so I have no personal experience with this myself.
> >
> > 73
> >
> > Sverre
> > LA3ZA
> >
http://www.qslnet.de/la3za/> >
>
> _______________________________________________
> 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>
Subscriber Info (Addr. Change, sub, unsub etc.):