Re: [Elecraft] K3EXREF question

2016-03-08 Thread Chuck - AE4CW 
Elecraft recently posted a modification to the K3REF to correct a problem
caused by the K3EXREF.  Though specific to frequency changes noticeable on
on 2M and 6M, I suspect it may directly relate to this discussion.
http://www.elecraft.com/K3/mods/K3EXREF%20freq%20shift%20fix.pdf
---
Chuck, AE4CW



-
---
Chuck, AE4CW
--
View this message in context: 
http://elecraft.365791.n2.nabble.com/K3EXREF-question-tp7614972p7615040.html
Sent from the Elecraft mailing list archive at Nabble.com.
__
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

Re: [Elecraft] K3EXREF question

2016-03-08 Thread Lyle Johnson 

Almost.

The TCXO has no control input and is not tuned; it is only measured.

The measurement information is passed to the radio's MCU which then uses 
the data to determine the correct value to command the synthesizer(s), 
drive the REF CAL display, and so forth.


73,

Lyle KK7P

The K3EXREF circuit is essentially a AFC (sort of) where a highly 
accurate 10-MHz reference is used to measure the frequency of the TCXO 
and send a frequency correction "word" to control the TCXO so that the 
error from 49.380 MHz is removed...


__
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

[Elecraft] K3EXREF question

2016-03-08 Thread ANDY NEHAN 
Thanks guys for the detailed and thorough replies - I understand it now!!
Andy G4HUE
__
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

Re: [Elecraft] K3EXREF question

2016-03-07 Thread Edward R Cole 
The K3EXREF circuit is essentially a AFC (sort of) where a highly 
accurate 10-MHz reference is used to measure the frequency of the 
TCXO and send a frequency correction "word" to control the TCXO so 
that the error from 49.380 MHz is removed.


As I understand it this comparison is done about every 
4-seconds.  The TCXO drifts with temperature so it will definitely 
change when you first power on the K3.  This drift will slow at some 
point and hover around a offset level (mine is about 49.380.080.  The 
TCXO is actually tuned to correct from that so REF*CAL is only 
showing the amount of offset that is being corrected.  Output of the 
TCXO is not 80-Hz high.  It would be if the EXREF did not correct it.


I have the K3/10 so only have the 12w PA which does not add as much 
heat in transmit as the 100w PA.  So that lessens the amount of 
temperature drift of the TCXO.  The TCXO-3 is better than the std 
TCXO so the improvement the EXREF makes is better with it.  On 
transmit on 28-MHz using the EXREF, I see approx. +/- 2 Hz frequency 
error with the TCXO-3.  This is equivalent to 0.1 ppm.  Without the 
EXREF my error is five time larger or about +/- 14 Hz.


There is still a slight amount of frequency drift since the TCXO is 
operating normally in between the times the 10-MHz reference checks 
and corrects frequency error.  This explains why a small amount of 
drift still occurs vs what happens with a phase-locked 
oscillator.  The result is that the frequency will appear to look 
like a ramp waveform over the 4-second interval between corrections.


The reason for choosing this form of frequency control is it 
preserves the excellent low phase noise of the K3.  PLL are difficult 
to make with as low phase noise.


If any of this is incorrect, perhaps one of the Elecraft engineers 
will correct what I wrote.


73, Ed - KL7UW
http://www.kl7uw.com
"Kits made by KL7UW"
Dubus Mag business:
dubus...@gmail.com

__
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

Re: [Elecraft] K3EXREF question

2016-03-07 Thread Kevin Stover 

I believe that is the way it is.
53/1000 of a hertz over an hour?
I'd give that up all day everyday for the spectacular lack of phase 
noise in the K3s or K3 with the new synth.

It's not a cesium clock.

On 3/7/2016 8:02 AM, David Anderson wrote:

I -think- the way it works is that when the K3EXREF is locked with the external 
frequency standard on 10 MHz, this is used to measure the frequency of the 
TCXO. The value of that frequency measurement is then put into the K3 REFCAL 
setting. If the TCXO drifts slightly as they all will, then the frequency 
difference is detected and the value in REFCAL is changed to match, hence 
keeping the frequency of the K3 correct, without actually phase locking the 
TCXO to an external reference which could degrade the low phase noise 
performance of the K3's synth.

Basically the K3EXREF is doing the same thing automatically as you would 
manually when doing the calibration, by measuring the TCXO frequency and 
storing that value in REFCAL. The K3EXREF acting a frequency counter with a 
high stability external 10 MHz reference.

Hope I have that right.

So, it would be normal for the value in REFCAL to change as things warm up even 
with the external reference into the K3EXREF, because the TCXO is not locked, 
just measured.


73 from David GM4JJJ





--
R. Kevin Stover
AC0H
ARRL
FISTS #11993
SKCC #215
NAQCC #3441


---
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus

__
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

Re: [Elecraft] K3EXREF question

2016-03-07 Thread David Anderson 
I -think- the way it works is that when the K3EXREF is locked with the external 
frequency standard on 10 MHz, this is used to measure the frequency of the 
TCXO. The value of that frequency measurement is then put into the K3 REFCAL 
setting. If the TCXO drifts slightly as they all will, then the frequency 
difference is detected and the value in REFCAL is changed to match, hence 
keeping the frequency of the K3 correct, without actually phase locking the 
TCXO to an external reference which could degrade the low phase noise 
performance of the K3's synth.

Basically the K3EXREF is doing the same thing automatically as you would 
manually when doing the calibration, by measuring the TCXO frequency and 
storing that value in REFCAL. The K3EXREF acting a frequency counter with a 
high stability external 10 MHz reference.

Hope I have that right.

So, it would be normal for the value in REFCAL to change as things warm up even 
with the external reference into the K3EXREF, because the TCXO is not locked, 
just measured.


73 from David GM4JJJ

> On 7 Mar 2016, at 11:01, David Pratt  wrote:
> 
> Andy - Without the K3EXREF connected, the REF CAL frequency will be
> fixed and the K3 will drift, albeit very slightly, particularly when it
> is first switched on.  With K3EXREF locked with your 10MHz standard the
> REF CAL frequency will vary to correct any drift in the K3. If you
> measure the output frequency of your K3 with an accurate frequency
> meter, such as a digital counter locked to a standard, you will find
> that your K3 is stable to within +/- a couple of Hertz.
> 
> 73 de David G4DMP
> 
> In a recent message, ANDY NEHAN  writes
>> Sometime ago I installed the K3EXREF which I feed from an external
>> 10MHz double oven Xtal oscillator. I am confident the K3EXREF is
>> installed and configured correctly as when in use and the external
>> oscillator is connected the front panel says REF*CAL with the *
>> blinking. Attempting to change the local oscillator frequency gives the
>> message "Locked" just as the manual says.
>> However, I am puzzled as the local oscillator frequency display slowly
>> drifts down from 49.379.675Hz to 49.379.622Hz over a period of at least
>> an hour from K3 switch on.  I leave the external oscillator on
>> permanently. I was expecting the local oscillator to rapidly get to its
>> final frequency. Can someone explain whats happening as I am puzzled??
>> My firmware is the latest version.
>> Andy G4HUE
> -- 
> + - - - - - - - - - - - - - - - - +
> | David M Pratt, Kippax, Leeds.   |
> | Website: http://www.g4dmp.co.uk |
> + - - - - - - - - - - - - - - - - +
> 
> __
> 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 gm4...@yahoo.co.uk
__
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

Re: [Elecraft] K3EXREF question

2016-03-07 Thread David Pratt 
Andy - Without the K3EXREF connected, the REF CAL frequency will be
fixed and the K3 will drift, albeit very slightly, particularly when it
is first switched on.  With K3EXREF locked with your 10MHz standard the
REF CAL frequency will vary to correct any drift in the K3. If you
measure the output frequency of your K3 with an accurate frequency
meter, such as a digital counter locked to a standard, you will find
that your K3 is stable to within +/- a couple of Hertz.

73 de David G4DMP

In a recent message, ANDY NEHAN  writes
>Sometime ago I installed the K3EXREF which I feed from an external
>10MHz double oven Xtal oscillator. I am confident the K3EXREF is
>installed and configured correctly as when in use and the external
>oscillator is connected the front panel says REF*CAL with the *
>blinking. Attempting to change the local oscillator frequency gives the
>message "Locked" just as the manual says.
>However, I am puzzled as the local oscillator frequency display slowly
>drifts down from 49.379.675Hz to 49.379.622Hz over a period of at least
>an hour from K3 switch on.  I leave the external oscillator on
>permanently. I was expecting the local oscillator to rapidly get to its
>final frequency. Can someone explain whats happening as I am puzzled??
>My firmware is the latest version.
>Andy G4HUE
-- 
 + - - - - - - - - - - - - - - - - +
 | David M Pratt, Kippax, Leeds.   |
 | Website: http://www.g4dmp.co.uk |
 + - - - - - - - - - - - - - - - - +

__
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

Re: [Elecraft] K3EXREF question

2016-03-07 Thread Roger 
Hi Andy,
I have the same (hardware) constellation and get similar results.



--
View this message in context: 
http://elecraft.365791.n2.nabble.com/K3EXREF-question-tp7614973p7614974.html
Sent from the Elecraft mailing list archive at Nabble.com.
__
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

[Elecraft] K3EXREF question

2016-03-07 Thread ANDY NEHAN 
Sometime ago I installed the K3EXREF which I feed from an external 10MHz double 
oven Xtal oscillator. I am confident the K3EXREF is installed and configured 
correctly as when in use and the external oscillator is connected the front 
panel says REF*CAL with the * blinking. Attempting to change the local 
oscillator frequency gives the message "Locked" just as the manual says.
However, I am puzzled as the local oscillator frequency display slowly drifts 
down from 49.379.675Hz to 49.379.622Hz over a period of at least an hour from 
K3 switch on.  I leave the external oscillator on permanently. I was expecting 
the local oscillator to rapidly get to its final frequency. Can someone explain 
whats happening as I am puzzled??
My firmware is the latest version.
Andy G4HUE
__
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

[Elecraft] K3EXREF question

2016-03-07 Thread ANDY NEHAN 
Sometime ago I installed the K3EXREF which I feed from an external 10MHz double 
oven Xtal oscillator. I am confident the K3EXREF is installed and configured 
correctly as when in use and the external oscillator is connected the front 
panel says REF*CAL with the * blinking. Attempting to change the local 
oscillator frequency gives the message "Locked" just as the manual says.
However, I am puzzled as the local oscillator frequency display slowly drifts 
down from 49.379.675Hz to 49.379.622Hz over a period of at least an hour from 
K3 switch on.  I leave the external oscillator on permanently. I was expecting 
the local oscillator to rapidly get to its final frequency. Can someone explain 
whats happening as I am puzzled??
My firmware is the latest version.
Andy G4HUE
__
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