Don: I think there may be a design error here. First clock crystals of the variety used in the K3 are dollar items in qualities of one. I have bought them in 1000 piece quantities for 50 cents. They are available from many vendors. Second the K3 design places a 33pf capacitor (C60) on the high side of the crystal to ground. However the clock chip manufacturer (see the data sheet at http://www.nxp.com/documents/data_sheet/PCF8563.pdf) suggests a 5 to 25pf NPO variable at this node. They also specify a maximum of 25pf on the node so the 33pf fixed value is actually out of spec. Furthermore if the 33pf cap is not NPO or COG grade it will have a poor temperature coefficient. This could easily explain the wide range of accuracy seen by users.
I would hope that Elecraft would offer a 5-25 NPO trimmer upgrade. When, properly trimmed, we should be able to get the same accuracy as that $10 watch. 73, Fred, AE6QL -----Original Message----- From: Elecraft [mailto:elecraft-boun...@mailman.qth.net] On Behalf Of Don Wilhelm Sent: Thursday, November 27, 2014 2:33 PM To: elecraft@mailman.qth.net Subject: Re: [Elecraft] re K3 timekeeping Because the Elecraft receiver is not designed to sync with those multiple time signals, it is only capable of receiving them, and you can use them to sync the time with the Elecraft RTC. A receiver is not a watch! The main difference is quantity of the precision crystals required to maintain a few seconds per month accuracy that can be purchased. Timex can easily purchase them at a low price based on an order of 10,000 or 100,000 or even 1 million. Elecraft could only swing a deal on a purchase quantity of 100 or 1000. The quantity pricing difference is extreme. The K2, K3, KX3 are known for having fine receivers, that does not mean they are also precision timepieces. The RTC is meant to be an aid to logging when no other means is available. When working in the home shack, use computer time or some "Atomic Clock" to provide you with accurate time. When operating portable, set the Elecraft clock to the correct time before your outing. It will be sufficiently accurate for logging purposes over the weekend event or even the weeklong event. Remember "logging accuracy" rather than precise time to the nanosecond. Alternately, wear your Timex (or whatever) and ignore the Elecraft gear clock. If I want to know the time, I instinctively look at my wrist, it is a habit developed over many years. It is much quicker and more reliable than dialing up the time on any of my radios. 73, Don W3FPR On 11/27/2014 4:58 PM, Barry wrote: > Don Wilhelm-4 wrote >> The K3 RTC depends on the crystal and the associated capacitors. It >> is not a precision device, > So how come a $10 watch keeps better time than a $3K xcvr (that has > access to multiple time signals)? :-) Barry W2UP > ______________________________________________________________ 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 Message delivered to fptowns...@earthlink.net ----- No virus found in this message. Checked by AVG - www.avg.com Version: 2015.0.5577 / Virus Database: 4223/8640 - Release Date: 11/27/14 ______________________________________________________________ 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 Message delivered to arch...@mail-archive.com
