New K3EXREF results
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I just completed the install of my K3EXREF, and am feeding the 10MHZ reference from a Trimble Thunderbolt.
After a couple of hours of warm up and settling out my reference osc is reading 49.379.945. I have the OXCO and was expecting to have better results that are closer to 49.380.000. Are my expectations unrealistic? Any suggestions? Mark Goecke KC5VF ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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When the radio is warm, mine sits around 49.380.071. About 49.380.015 cold.
Did you do a manual calibration and compare it to the GPS-stabilized value? Or just check cal against WWV. It's probably fine. Grant/NQ5T On Oct 29, 2011, at 4:38 PM, Mark Goecke wrote: > I just completed the install of my K3EXREF, and am feeding the 10MHZ reference from a Trimble Thunderbolt. > > After a couple of hours of warm up and settling out my reference osc is reading 49.379.945. I have the OXCO and was expecting to have better results that are closer to 49.380.000. > > Are my expectations unrealistic? Any suggestions? > > Mark Goecke KC5VF ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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In reply to this post by KC5VF
Results seem to be different for every TCXO. My REF*CAL starts about
around .693 and settles to .778 after a couple hours. I borrowed a Rubidium clock from work and got nearly identical results. The only difference was freq source, so the chracteristics must be K3-specific. Another K3 owner and I ran it on his (#35xx-something) and his started at .717 and settled out at .798. Same basic trends all around. I'm also using the Trimble TB here; it's been active for ~six months and results are always the same. The K3's resolution is still +/- 1 Hz, but now you know your rig uses the right ref osc frequency. The REF*CAL value shown is the compensation for the external freq reference. I'm not sure how Wayne calculates what's shown; maybe he'll publish his secret sauce recipe... 73, matt W6NIA On Sat, 29 Oct 2011 16:38:41 -0500, you wrote: >I just completed the install of my K3EXREF, and am feeding the 10MHZ reference from a Trimble Thunderbolt. > >After a couple of hours of warm up and settling out my reference osc is reading 49.379.945. I have the OXCO and was expecting to have better results that are closer to 49.380.000. > >Are my expectations unrealistic? Any suggestions? > >Mark Goecke KC5VF >______________________________________________________________ >Elecraft mailing list >Home: http://mailman.qth.net/mailman/listinfo/elecraft >Help: http://mailman.qth.net/mmfaq.htm >Post: mailto:[hidden email] > >This list hosted by: http://www.qsl.net >Please help support this email list: http://www.qsl.net/donate.html Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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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 <[hidden email]> wrote: From: Matt Zilmer <[hidden email]> Subject: Re: [Elecraft] New K3EXREF results To: "Mark Goecke" <[hidden email]> Cc: [hidden email] Date: Saturday, October 29, 2011, 5:54 PM Results seem to be different for every TCXO. My REF*CAL starts about around .693 and settles to .778 after a couple hours. I borrowed a Rubidium clock from work and got nearly identical results. The only difference was freq source, so the chracteristics must be K3-specific. Another K3 owner and I ran it on his (#35xx-something) and his started at .717 and settled out at .798. Same basic trends all around. I'm also using the Trimble TB here; it's been active for ~six months and results are always the same. The K3's resolution is still +/- 1 Hz, but now you know your rig uses the right ref osc frequency. The REF*CAL value shown is the compensation for the external freq reference. I'm not sure how Wayne calculates what's shown; maybe he'll publish his secret sauce recipe... 73, matt W6NIA On Sat, 29 Oct 2011 16:38:41 -0500, you wrote: >I just completed the install of my K3EXREF, and am feeding the 10MHZ reference from a Trimble Thunderbolt. > >After a couple of hours of warm up and settling out my reference osc is reading 49.379.945. I have the OXCO and was expecting to have better results that are closer to 49.380.000. > >Are my expectations unrealistic? Any suggestions? > >Mark Goecke KC5VF ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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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 <[hidden email]> wrote: > >From: Matt Zilmer <[hidden email]> >Subject: Re: [Elecraft] New K3EXREF results >To: "Mark Goecke" <[hidden email]> >Cc: [hidden email] >Date: Saturday, October 29, 2011, 5:54 PM > >Results seem to be different for every TCXO..... ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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On Oct 30, 2011, at 8:01 AM, Matt Zilmer wrote: > 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. That's correct. We don't need REF CAL to be exactly 49,380,000 Hz because we take the actual frequency of the reference into account in firmware when setting up the synthesizer. The 2nd LO is compensated at the same time, at 1/6th the rate (because of the /6 relationship between that and the 1st LO). If there's a K3EXREF installed, its microcontroller measures the frequency of the 49 MHz reference down to 1 Hz using the 10 MHz external reference as a timebase. This data is sent to the K3's main MCU, which then uses it to "capture" the normal REF CAL value. One advantage of this method (frequency-locked loop) is that no matter how noisy the external reference is--possibly due to being distributed around the shack--it can't have any effect on the radio's RX or TX noise floor. It is used only as a counting gate. 73, Wayne N6KR ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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