David Pratt wrote: >Page 17 of the K3 Owner's Manual (Rev D2) shows an SMA connector for >"Input for external standard frequency reference" for which a KREF3-EXT >option purports to be available eventually. I understand from what has >been said earlier is that this will be for a 10MHz standard so you will >need to use the 60kHz MSF signal to lock a 10MHz TCXO or use a GPS, >Rubidium or Caesium standard. >
The schematic of the KSYN3 board shows a header (J4) with connections to the 10MHz input, the 49.380MHz output from the existing oscillator module and a V_ctrl line going back to the oscillator module. This suggests that the KREF3-EXT module will have a phase-locked loop to lock the oscillator to 10MHz. (Also on J4 is a mysterious "100Hz" bus which wanders around many other areas of the K3... anyone know what that is?) However, phase locking to an external reference still doesn't mean that the K3 will be precisely on frequency. Due to the internal arithmetic of the K3's synthesis and mixing scheme, the frequency you see on the display is not quite the frequency you actually get. As Wayne pointed out on 17 November, "this translates to a VCO step size of about 0.5 Hz on 160 m, 1 Hz on 20 m, and 2 Hz on 6 m. Other bands are between these values." What the KREF3-EXT module should be able to deliver is complete freedom from frequency drift, for almost all practical purposes. There could also be great communication value in being able to lock a pair of K3s to the same global GPS standard, even when they are half a world apart In the meantime, the K3 already has the most important kind of frequency and phase locking - between its own two receivers for true diversity reception. -- 73 from Ian GM3SEK ______________________________________________________________ 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
