http://elecraft.85.s1.nabble.com/K3-slightly-off-frequency-tp7629167p7629203.html
You will be able to quickly tell.
> On Apr 9, 2017, at 6:11 PM, Ian White <
[hidden email]> 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:
[hidden email]] On Behalf Of
>> brian
>> Sent: 09 April 2017 18:33
>> To:
[hidden email] >> '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
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