If I understand correctly, your near Fremont CA. I had a two week turn around in Watsonville for Calibration. The charge was about $100. I drove it there. Saved the postage charges. Don't forget to call to obtain authorization for the return. It's also a good time to get hardware updates. Ted wp4cw.
On Apr 9, 2017 9:16 AM, Mike Harris <mike.har...@horizon.co.fk> wrote: > > Immediate apologies, this is a tad long but hopefully interesting. > > My K3 has the new synths (2), K144XV with REF Lock option and all is > well without doing the KREF3 modification. I guess this is an it either > works or it don't situation. > > With respect to the post about off frequency, not a simple answer. > > Firstly accuracy and resolution or precision are not to be confused, one > doesn't imply the other. The K3 display may read to 1Hz but that doesn't > mean it is accurate to 1Hz. If folks in a net all set their various > digital displays to the same frequency it doesn't mean they are all on > the same frequency. > > As has been mentioned there is a perfectly good method of adjusting > calibration detailed in the handbook using WWV. It doesn't directly tune > or otherwise adjust the reference oscillator (TCXO) but lets whatever is > involved with controlling the synths what the reference frequency really > is so that the error can compensated for mathematically. That is my > understanding. I have been using this WWV method for the past nine years > and was convinced that the TXCO was probably drifting with age and have > often said that the CONFIG: REF CAL is not a one off adjustment. This > unfortunately turns out not to be the whole story. > > Now it has to be said, the TXCO does drift, shock, horror. The high > stability option is described as being +/-1ppm but actually seems to > achieve 0.5ppm, at least mine does. How do I know this? I don't have a > frequency counter, or at least I didn't and in fact you don't need one > as will be discovered later. What I do have is the K3 external reference > frequency lock option fitted and recently purchased a Leo Bodnar GPS > disciplined reference clock which provides the necessary 10MHz drive for > the ext ref option. With a new toy you have go to play and what I > discovered follows. > > With the GPS source up and running, turning on the K3 and enabling the > external ref feature the REF CAL measured TXCO frequency will be > displayed, counted by the ref lock module. This frequency will be seen > to change with warm up. My TXCO has a positive drift of approx 26Hz+/- a > couple in the first three minutes, for the next 30 minutes it drifts a > further 6Hz. Thereafter it slowly drifts until after four hours it tops > out at +57Hz or so and by this measurement method stops drifting. > > However, there is more. At the same time as noting the REF CAL frequency > every minute, for the first hour, I also recorded the front panel (FP) > temperature. This started at 23C and over the measurement period > increased to 38C. It was observed that the rise in FP temp and the drift > follow a similar trajectory. As would be expected. > > I have monitored the REF CAL frequency for a couple of months now and > note that the TXCO drift on my unit always maxes out at more or less the > same reading. > > I have reached the conclusion that if at least two hours of warm up are > allowed and a WWV cal operation is then performed you will be in a > pretty good place with respect to total drift and subsequent overall > frequency (dial) accuracy. > > It is easy to discover the pattern and extent of the drift of the TXCO > in your K3 without any external measuring equipment, external ref locks > or such. > > 1. From cold tune to a WWV frequency you will be able to receive > reliably for a few hours. Higher the better. > 2. Wait 5 minutes or you will be chasing a moving target. > 3. Perform a REF CAL and note the reading. > 4. Perform a REF CAL every half hour, less if you feel like it and note > the readings. > 5. Eventually the reading will really slow down and more or less stop > changing. > 6. Choose a reading that indicates that the bulk of the drift has > happened, (1-2 hours) > 7. Set REF CAL to that reading and sleep well. Good enough for HF. > > Given the highest and lowest frequency readings a further experiment can > be performed to discover the consequences of the TXCO drift on dial > accuracy. It only takes a few minutes. > > 1. Set REF CALL to the lowest recorded frequency and tune the K3 to a > stable test frequency, I used my XG3, note the "dial" reading in fine > frequency display, 3 digits after the decimal point. I used the CW auto > spot feature to do the final tune. > 2. Set REF CAL to the highest recorded frequency and retune the K3 as > above noting the "dial" frequency. > > The lowest to highest REF CAL frequency is the total TXCO drift in Hz. > The lowest to highest "dial" frequency will indicate the consequence of > that TXCO drift in Hz. You will be pleased to note that the two do not > match. The K3 tuned frequency change is rather less than the TXCO drift. > > Reset the REF CAL reading to that you previously chose to be your K3's > sweat spot. > > The above shows why I was wrong in relating the REF CAL frequency > changes to TXCO ageing. In reality it all comes down to warm up time. > > I hope this was worth the read. > > Regards, > > Mike VP8NO > > > > On 09/04/2017 05:51, Roger via Elecraft wrote: > > KREF3MDKT This modification increases the output levels from the KREF3 > > Reference Oscillato ______________________________________________________________ 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
