10 MHz is an industry standard. This is goof. However, you might want to consider a 1PPS GPS-trained input as well.
73, Gene K1NR On Mon, 14 Jun 2010 16:15:39 -0700 Wayne Burdick <n...@elecraft.com> wrote: > There appears to be more demand for this than we thought, > so we're > looking into it again. > > Note that our planned external reference implementation > would not > require an exact 49.380000-MHz reference oscillator > signal. It also > doesn't require a pin-1 control voltage input on the TCXO > module > itself, as suggested earlier. It should work with any > existing K3 > TCXO, either +/- 5 or +/- 1 PPM. > > If you're interested, here are the details: > > A new REF-lock module would be designed that plugs into > the small 8- > pin connector near the top of the KREF3 PCB. The user's > 10-MHz > reference signal would be routed from the rear panel to > the TMP > connector on the KRE3 (this connector faces forward, into > the DSP/ > front panel area). > > A microcontroller on the REF-lock module would be clocked > by the 10- > MHz reference. If the signal were present, the > microcontroller would > continuously measure (and average) the frequency of the > 49.38 MHz > oscillator, obtaining a value to the nearest 1 Hz. > Hysteresis would be > applied to prevent "hunting," so the actual accuracy spec > would > probably be +/- 2 Hz. This translates to about +/- 1 Hz > in operating > frequency on 20 m. > > Approximately once per second, the module would report > the actual > reference frequency to the K3's main MCU via a slow > digital data line > (labeled "100HZ" on the RF and KREF3 schematics). The > main MCU would > use this to calibrate the REF CAL value normally entered > by the user. > There would be no noticeable impact on performance. > > If the 10 MHz external signal were not present, the > user's normal REF > CAL value would be used. > > Let me know if you have thoughts on this implementation. > > 73, > Wayne > N6KR > > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:Elecraft@mailman.qth.net > > This list hosted by: http://www.qsl.net > Please help support this email list: > http://www.qsl.net/donate.html --------------------------------------------------------------------- Web mail provided by NuNet, Inc. The Premier National provider. http://www.nni.com/ ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
