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.
You are welcome to try the single capacitor solution, but do beware of the pitfalls. If you would like further documentation on padding the BFO, download the K2 AtoB instructions and look at the 2nd column of page 12. 73, Don W3FPR > -----Original Message----- > > All the components look right. I guess I've got the dreaded high > Q crystals. I've noticed in the Elecraft archives that it is > possible to put a capacitor at the junction of X3/X4 to ground. > Which is the preferred method? > > Thanks. > > > > From: "Don Wilhelm" <[EMAIL PROTECTED]> > > Date: 2005/12/07 Wed AM 09:30:04 PST > > To: <[EMAIL PROTECTED]>, > > <[email protected]> > > Subject: RE: [Elecraft] K2 BFO Test > > > > Ted, > > > > Yes, you should get the BFO range and frequency correct - you > can continue > > with no extra effort, but it must be resolved eventually, and > there is no > > time like the present to do it. > > > > Check the values of the capacitors C173 and C174, and while you > are at it, > > check C169 too. Additionally, check the varactors D37 and D38 for the > > correct type (1SV149 - the smaller ones) qne proper > orientation. Be certain > > the BFO crystals were the ones you soldered in - they are > typically marked > > ECS D4.91 -S > > > > If you find all the above correct, you may have to pad > Capacitors C173 and > > 174. Should that become necessary, use 47 pf in parallel with > C174 and 120 > > pf in parallel with C173. The padder capacitors will lower the low > > frequency end more than the high frequency end of the range, so > it should > > work for you - but do the padding only if there is nothing else > wrong with > > the components. > > > > 73, > > Don W3FPR > > _______________________________________________ Elecraft mailing list Post to: [email protected] 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
