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You will be able to quickly tell. Va3mw > On Apr 9, 2017, at 6:11 PM, Ian White <[email protected]> wrote: > > K3KO wrote: > >> With the standard synthesizers, as one tunes up the band the true >> frequency deviates from the displayed by up to +/-4 Hz. There are > times >> when one tunes up and the RX actually goes to a lower frequency. Same >> problem when tuning downwards. In other words, there is electronic >> "backlash". One has no way of knowing which point of this sawtooth >> error curve you are when choosing to calibrate to WWV. This is >> essentially fixed with the new synthesizers. > > Back in the day, Elecraft informed us about that cyclical error problem > with the old synthesizer. It would now be good to have a definitive > statement about the frequency setting accuracy in the new synthesizer. > > The same applies to the TCXO error correction by the KREF3 module. Since > corrections are applied by rewriting the declared value of the 48MHz > reference frequency, presumably this can still only be changed in 1Hz > increments. > > A related question (raised by Don's post, just in) is the magnitude of > any difference between the displayed sidetone pitch and the actual value > within the synthesizer? > > 73 from Ian GM3SEK > > >> -----Original Message----- >> From: Elecraft [mailto:[email protected]] On Behalf Of >> brian >> Sent: 09 April 2017 18:33 >> To: [email protected] >> 'Elecraft Reflector' >> Subject: Re: [Elecraft] K3 slightly off frequency >> >> All true. Note that the standard oscillator takes two hours to stop >> drifting instead of four. Also the TCXO isn't. There is no > temperature >> feedback implemented. One is essentially seeing the stability of the >> native oscillator. Too bad feedback isn't implemented, I'd bet a lot > of >> drift noted would disappear. >> >> Not discussed is the "last digit" syndrome. Only believe the last > digit >> displayed if you can check that it is accurate. >> >> >> 73 de Brian/K3KO >> >> >>> On 4/9/2017 16:16 PM, Mike Harris 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 Oscillator to provide proper drive levels for K3 > transceivers >>>> equipped with a KSYN3A synthesizers the KRX3 or KRX3A sub receiver >> and >>>> the >>>> K144XV 2-meter transceiver. >>>> >>>> 73, Roger >>> ______________________________________________________________ >>> Elecraft mailing list >>> Home: http://mailman.qth.net/mailman/listinfo/elecraft >>> Help: http://mailman.qth.net/mmfaq.htm >>> Post: mailto:[email protected] >>> >>> This list hosted by: http://www.qsl.net >>> Please help support this email list: http://www.qsl.net/donate.html >>> Message delivered to [email protected] >> ______________________________________________________________ >> Elecraft mailing list >> Home: http://mailman.qth.net/mailman/listinfo/elecraft >> Help: http://mailman.qth.net/mmfaq.htm >> Post: mailto:[email protected] >> >> This list hosted by: http://www.qsl.net >> Please help support this email list: http://www.qsl.net/donate.html >> Message delivered to [email protected] > > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[email protected] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Message delivered to [email protected] ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [email protected]
