Any news on the External Reference Option ? 73 Trevor G0KTN
-------- Original Message from Wayne N6KR dated 14 June 2010 -------- 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
