K2 PLL Reference Oscillator Range. Further to my previous posting: the problem was not insensitive counter but was in some way connected with the RIT/XIT control. The low frequency reading BAND- is now stable but is too low. BAND+ is 12099 and BAND- 12078 giving a range of over 20kHz which is outside specification.
I have checked the circuit and all seems to be OK. U5 pin7 (U6 pin3) is 4.06 at BAND+ and 0.01at BAND- which seems OK according to the circuit diagram. U6 pin1 is 7.48 and 0.00. This again seems OK as U6A has a gain of about 2 with a small -ve bias resulting from the thermistor mod. D16 and D17 are unbiased at the low end. (They actually self bias from the RF ro a small +ve voltage at R19/C100). This seems to be bad practice as the capacity will vary widely from component to component and result in widely varying reference oscillator range. Hence my 20kHz range? Am I mistaken? Is there a fix for this? John G3NYX _______________________________________________ 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
