Hi Bob, I know for certain the the actual VFO shift is not reflected in the REF*CAL value. Otherwise, we'd all be seeing massive frequency error on RX and TX. The reference frequency is used in the DDS to derive the injection freq, so the error should be reduced substantially by that alone. The ref freq is also divided down by 6 to get the 8.23MHz 2nd LO injection freq. If Wayne's design followed others (Motorola for one), the shift in LO and first IF would buck (cancel) each other to some extent.
I let the K3 (#24) settle for about 2 hours this morning and watched the REF*CAL go from .693 to .741 at present. VFO A sitting square on WWV 5MHz, and beat freq ran from about 2Hz at startup to 4Hz now. Without the K3EXREF, it ran a little looser: something like 15 Hz range top to bottom. There's something else going on here, but would require Wayne's analysis to clarify. I couldn't find a schematic of the K3EXREF in the original manual, though it's probably available. Since the 'REF board bolts onto the reference freq oscillator, it's probably compensating the reference. At least that's my take on it. The REF*CAL values I've seen (mine and everyone else's) are all in the same range and no one's had any problem staying on frequency. 73, matt W6NIA On Sat, 29 Oct 2011 22:11:16 -0700 (PDT), you wrote: >Hi Matt, > > I'm in Ohio and waiting for the storm to pass and roads to be >cleared before going back to NJ so do not have the hard data available but I >ran checks too. In my case the reference is an external Trimble Thunderbolt >and I also saw shifts in the same range. Even if the first few hours are >ignored, for warmup purposes, the shift was in excess of 50HZ. Your two >cases indicate 81 & 85 HZ. If this is only the change in the reference >oscillator it seems to be over the 1 PPM spec. However I was never sure if I >was accounting for all error sources in watching this oscillator correction. >The +/- 2 HZ locking error at 10MHZ would be +/-10 HZ at 50MHZ alone. I only >used the values that were shown when the Trimble Thunderbolt was in >disciplined mode. > > Hopefully someone will comment and point out the errors in my >thinking. Even if over the 1 PPM spec it is still the most stable and >accurate receiver I've ever owned. The temperature compensation data is not >being used as far as I know and I'm not close to the .5 PPM given as typical. > >73, >Bob >K2TK ex KN2TKR (1956) & K2TKR > >--- On Sat, 10/29/11, Matt Zilmer <[email protected]> wrote: > >From: Matt Zilmer <[email protected]> >Subject: Re: [Elecraft] New K3EXREF results >To: "Mark Goecke" <[email protected]> >Cc: [email protected] >Date: Saturday, October 29, 2011, 5:54 PM > >Results seem to be different for every TCXO..... <snip> ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
