Hi Don, The inductor I removed measures 12.9 uH - seems to be in tolerance. My guess is the crystals (X1) had too high Q. I got two - one with the the PLL temp compensation and one in the BFO upgrade. Tried each of the crystals - both had the same dial error result.
You are right that instructions do say that, but I posted the results of this test in my original post. The only messages I got were to set the 4 Mhz oscillator (using several different methods), run CAL PLL and CAL FIL (vary each entry). None of this addressed the real issue. I had installed the components correctly and I just could not understand what went wrong. It ends up being a design flaw (component variation exceeded the design parameters). Oh well, I learned a lot even though the radio sat idle for a year. Can't contest or qsl much when you don't know what frequency you really are on. :) Another person on the list had the same problem and mentioned it in a single post - which had no response or update to the FAQ list. That post gave a hint that a slightly low VCO frequency was resposible for dial error. Don, I am not picking on you as you have provided help tirelessly to hundreds of people on this list (and to me several times). Thank you. All I am asking is that Elecraft update their FAQ to include this critical info. Thanks, Paul AD5IW On Wed, 3 Dec 2008, Don Wilhelm wrote: > Paul, > > The A to B instructions do state that the PLL reference high frequency is > 'typically 12097 to 12100 kHz'. > Yours was clearly not in the typical range, and indicated that something was > awry. > You are correct that there should be a statement that the upper frequency must > be above 12096 kHz. > > Incidently, a 12 uHy choke should provide a greater range than a 10 uHy. I am > wondering if the 12 uHy choke you received was really a 12 uHy. I am certain > it was marked as a 12 uHy - any chance that you can measure it to see if my > speculation is correct? > > 73, > Don W3FPR > > paul wrote: > > Last year, I upgraded my K2 from rev A to Rev B. Afterwards the dial was > > off by 12 KHz at 10MHz, even after setting the 4Mhz crystal, doing CAL > > PLL, CAL FIL more than 30 times. Yes, I followed every procedure posted > > and verified the 4 MHz clock accurately. Prior to the upgrade, the dial > > was right on. > > > > It turns out that the VCO max frequency must be at least 12096 khz or the > > dial calibration will be off. This should be in the FAQ, along with how > > to fix it in the upgrade instructions. > > > > After making the rev A to B mod, the VCO range was 12084.87 to 19094.44 > > creating the 12Khz dial error - no matter how many alignments attempted. > > > > Finally I just tried experimenting with the VCO. I put in another > > crystal in parallel with X1 (that came with the BFO upgrade) in X2. The > > VCO range was 12081.52 to 12098.17 which fixed the dial error, but the > > VCO was too wide at 17.19 Khz. > > > > I swapped out the 12uH inductor (L31) with the old 10uH inductor and got > > a VCO range of 12084.87 to 12094.44 - dial calibration was way off (Yes, > > CAL PLL and CAL FIL were run after each of these changes). > > > > Then I removed the second crystal at X2 that I had temporarly installed > > two steps above. VCO range now 12090.70 to 12097.63 - BINGO - the dial > > is dead on!!! The VCO is a little narrow at 6.93 Khz, but I have no > > plans to use 160 meters - so this should be ok. > > > > So the solution was to go back to the 10uH inductor. > > > > I have spent several weekends and nights trying to figure out this > > problem. While I have learned a lot doing this, please put this in a FAQ > > somewhere and save someone else the trouble. > > > > Paul > > AD5IW > > > > On Sun, 2 Dec 2007, paul wrote: > > > > > _______________________________________________ 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
