Hello James, You are correct on #1 and #2, as long as the signal amplitude feeding the K3EXREF is in the range of +4 dBm to +16 dBm. The Thunderbolt 10 MHz output is typically +12dBm (about 2.5V p-p), for example.
73, Rich AC7MA On 4/5/2011 12:11 PM, James Sarte (K2QI) wrote: > Hello group, > > It's been many months since I've posted here, much less actually done > something new with my K3. This topic has however piqued my interest. > Just so I understand fully, am I right in assuming then that the > following is correct: > > 1. Any reference oscillator operating at 10 MHz would work with the K3XREF? > 2. All that's needed for this to work is the K3XREF, updated > firmware, an accurate 10 MHz clock/oscillator, and a BNC cable? > 3. Trimble Thunderbolt seems to be a good, cheap product to try. Any > others that are> $100? > > What are the additional advantages of doing this other than knowing > you've pretty much eliminated any frequency drift? > > 73 de James K2QI > President UNARC/4U1UN > > On Tue, Apr 5, 2011 at 2:32 PM, Rich Heineck<ric...@frontier.com> wrote: >> The K3EXREF uses the 10 MHz standard as it's time base to measure the K3's >> TCXO and passes >> an error value to the K3's MCU every few seconds. No TCXO frequency control >> takes place, >> thus no increase in phase noise. Frequency compensation is done in software >> by >> automatically updating the REF CAL function. A relatively simple mechanism >> but effective :) >> >> For my installation, I'm using a Thunderbolt, an $11 active antenna from >> Digi-Key, and a >> 30' run of RG-6, which works nicely with the F connector on the Tbolt. >> >> 73, >> Rich AC7MA >> >> On 4/5/2011 10:35 AM, Leigh L. Klotz Jr WA5ZNU wrote: >>> ... >>> The K3XREF product that Elecraft is developing is, to my understanding, an >>> external disciplining interface for the TCXO in the K3. It's probably a >>> frequency counter / microprocessor which reads the internal oscillator and >>> the external 10 MHz reference, and when the internal oscillator doesn't >>> produce the right number of cycles in 10 million of the external >>> oscillator's cycles, it adjusts the voltage on the TCXO to bring it back >>> into spec. But if you do this too often, you'll introduce phase noise into >>> the K3 (think of it as FM-ing). Wayne N6KR has said it does this a few >>> times a second an has achieved a trade off between accuracy and phase noise. >>> (I presume he doesn't adjust during TX, for example.) >>> >>> I leave my K3 on most of the time, and I've found that it is seldom off more >>> than +/- 3 Hz. But the K3XREF would let it off +/- 1Hz as soon as you turn >>> it on, provided it's hooked up to your external reference. The actual >>> received frequency is only valid for one mode and one filter, once you >>> calibrate it, since when you shift modes or filters the offets of the >>> various internal IF stages varies. (Keep that in mind if you use the K3 for >>> the ARRL FMT.) >>> >>> Leigh/WA5ZNU > ______________________________________________________________ > 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
