There has been talk off and on from Wayne of completing the firmware that would interpret the TCXO cal figures. Given that, those who really want this (for whatever reason - I won't comment on that) could, with a separate precise frequency standard, actually develop their own TCXO cal figures which pretty much nailed temp change for a given K3. This would be better than figures for a stand-alone TCXO calibrated in a lab.
My add to that would be that an individual K3 could be brought into line on a curve that would be a fourth of the K3's spec. My take is that without dissing someone for WHY they want it, it IS possible and just another aspect of excellence that only lacks firmware to become reality. The TCXO cal interpret firmware would then become a tool which the OWNERS could perfect, and in turn can move into future products, including a utility that takes a precision calibration routine and automatically maxes the frequency stability for a given unit. It could also become a cottage industry for someone who got really good at it to calibrate K3's for temperature stability. Why not? 73, Guy. On Wed, Jun 29, 2011 at 9:19 AM, Brian Alsop <als...@nc.rr.com> wrote: > Guys, > > I'm curious what is the max front panel temp you're seeing after a > period of operating with significant transmit time? Also what is the > room temp at this value. > > The reason I ask has to do with the K3 Master Oscillator calibration > procedure and later drift. A detailed set of measurements with a stock > K3 indicates a good correlation of drift with front panel temperature. > With the standard oscillator, measurements indicate that the K3 drifts > about -1.2 Hz/C (.12ppm/C) degree at 10 MHz. Here a Rb 10MHz secondary > frequency standard was used as well as a counter to measure how the > audio tone changes vs time. This allows sub Hz changes to be observed. > > Normally one does the calibration receive only. In that case with an > ambient temp of 24C here, the front panel temp rises 34 C after 90 > minutes. I normally calibrate after such a warmup. > > If the front panel temp rises another 10C after periods of transmit, the > frequency could be off by about -12 Hz at 10 MHz (-60 Hz at 50 MHz). > Sure that's not a lot. But it says, perhaps one shouldn't knock > themselves off trying to be super accurate with the calibration. There > will be another couple or perhaps as much another 10 Hz (1ppm) error due > to transmiter heat buildup. The actual amount can probably never be > predicted. > > It is clear to me if one "needs" more accuracy, the high precision > oscillator option and/or locking to an external reference would be needed. > > I'd love to look at the high stability oscillator drift as well. > However, satisfying that curiosity for $100 isn't going to happen. > Perhaps someone out there with the high stability oscillator could > repeat the above measurements and report the results. > > 73 de Brian/K3KO > > > > > > ----- > No virus found in this message. > Checked by AVG - www.avg.com > Version: 10.0.1388 / Virus Database: 1516/3733 - Release Date: 06/29/11 > > ______________________________________________________________ > 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 > ______________________________________________________________ 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
