Rolf, Yes, re-do CAL FIL to properly reposition the filter passbands - the BFO controls that positioning, so any change in BFO frequency will cause a shift.
You should not need to run CAL PLL since the PLL reference oscillator has not been changed. Why does adding a capacitor change the frequency? The BFO is actually a VXO, and the frequency is controlled by changing the capacitance in the circuit - normally that is done by changing the voltage on the varicaps, but since your total capacitance range was slightly out of normal a small padder capacitor needed to be added. 73, Don W3FPR > -----Original Message----- > > Hello! > > After few weeks building incativity due to hot summer I'm back in my > shack. My K2 #4759 has been on the air several months. However, BFO > lower limit frequency didn't meet the required 4912.7 kHz > > Leigh, WA5ZNU sent me a mail which he had got from Gary from Elecraft. > Gary adviced to add 1-4pF NP0-capacitor to junction of X3 and X4. I mean > the lower junction in schematics. That is connected to L33. I added > 1.5pF NP0 capacitor on the bottom of the RF board. Other pin of > capacitor was soldered to ground pad of X4. > > BFO is now working OK. You can find the new frequencies below. Original > frequencies are shown in the brackets. > > BFO High Freq. 4917.17 kHz (4917.23 kHz) must be >= 4916.3 kHz > BFO Low Freq. 4912.50 kHz (4912.95 kHz) must be <= 4912.7 kHz > > I'd be interested in the technical report why adding a little cap to the > paralleel of L33 and series with parallel connected crystals lowered the > oscillator frequency. I'm not an engineer. But I'd like to understand. > > Should I make CAL FIL (and CAL PLL) again after this mod? I assume they > are not needed. > > Rolf Moberg > oh6kxl > -- No virus found in this outgoing message. Checked by AVG Anti-Virus. Version: 7.0.323 / Virus Database: 267.9.2/52 - Release Date: 7/19/2005 _______________________________________________ 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
