Elecraft

10 MHz external reference

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W1KSZ

Re: 10 MHz external reference - GPSDO

I am a tad confused over this issue. Perhaps I need to read up on how
Elecraft
controls frequency.

My understanding on a "Locked" frequency would infer that the result would
be
a LOT closer than 2 Hz @ 10 MHz.

Is there a detailed description of the process somewhere that I could read ?

73, Dick, W1KSZ

-----Original Message-----
From: Elecraft [mailto:[hidden email]] On Behalf Of David
Anderson
Sent: Friday, March 11, 2016 9:04 AM
To: [hidden email]
Cc: [hidden email]
Subject: Re: [Elecraft] 10 MHz external reference - GPSDO

You may want to have a look at this for some background on real world
frequency stability, and remember that the K3 isn't phase locked to the
external reference and is only going to be within 2Hz.

https://www.febo.com/pages/stability/

73 from David GM4JJJ

>
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Petr, OK1RP/M0SIS

Re: 10 MHz external reference - GPSDO

In reply to this post by GM4JJJ

Hi,

in case of such amount of bucks is planned to be spent for "ready to go" unit then Leo Bodnar is the very good choice but I preffer this "Low Jitter / Low Phase Noise" model:

http://www.force12inc.com/products/gps-locked-precision-frequency-reference-low-jitter-gps-clock-450-hz-to-800-mhz-output-custom-low-phase-noise-xtal-version.html

I know that it will not be utilized fully in case of just locking the K3 but it can be used in much more application in ham shack like MW etc.

73 - Petr, OK1RP

73 - Petr, OK1RP
"Apple & Elecraft freak"
B:http://ok1rp.blogspot.com
MeWe: https://bit.ly/2HGPoDx
MeWe: https://bit.ly/2FmwvDt

GM4JJJ

Re: 10 MHz external reference - GPSDO

In reply to this post by W1KSZ

There was a thread about this recently (last few days).

The instructions for the K3 give the spec as up to plus and minus 2Hz at 10 MHz.

73 from David GM4JJJ

> On 11 Mar 2016, at 16:55, Richard W. Solomon <[hidden email]> wrote:
>
> I am a tad confused over this issue. Perhaps I need to read up on how
> Elecraft
> controls frequency.
>
> My understanding on a "Locked" frequency would infer that the result would
> be
> a LOT closer than 2 Hz @ 10 MHz.
>
> Is there a detailed description of the process somewhere that I could read ?
>
> 73, Dick, W1KSZ
>
> -----Original Message-----
> From: Elecraft [mailto:[hidden email]] On Behalf Of David
> Anderson
> Sent: Friday, March 11, 2016 9:04 AM
> To: [hidden email]
> Cc: [hidden email]
> Subject: Re: [Elecraft] 10 MHz external reference - GPSDO
>
> You may want to have a look at this for some background on real world
> frequency stability, and remember that the K3 isn't phase locked to the
> external reference and is only going to be within 2Hz.
>
> https://www.febo.com/pages/stability/
>
> 73 from David GM4JJJ
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
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>
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> delivered to [hidden email]
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GM4JJJ

Re: 10 MHz external reference - GPSDO

In reply to this post by W1KSZ

Dick,

I found the reference to that figure I quoted, it is in the K3EXREF manual:

The K3EXREF option locks the K3's reference oscillator frequency to an external 10 MHz source by automatically controlling the REF CAL function. While locked to the external source, the K3’s reference oscillator frequency is maintained within 2 Hz. Since the K3EXREF does not phase lock the K3’s reference oscillator, the external 10 MHz source has no impact on the K3’s phase noise performance. For best performance we recommend your K3 be equipped with the KTCXO3-1 high stability (0.5 ppm typ.) reference oscillator.

73 from David GM4JJJ

Joe Subich, W4TV-4

Re: 10 MHz external reference - GPSDO

> While locked to the external source, the K3’s reference
> oscillator frequency is maintained within 2 Hz.

The K3's reference oscillator is 49.380 MHz (+/-) not 10 MHz.

The K3EXTREF uses the external 10 MHz signal to gate a counter
which counts the reference. That count is then used to adjust
the reference frequency. Maintaining the 49.380 MHz reference
+/- 2Hz is on the order
of 0.04 ppm.

73,

... Joe, W4TV

On 3/11/2016 1:07 PM, David Anderson wrote:

> Dick,
>
> I found the reference to that figure I quoted, it is in the K3EXREF
> manual:
>
> The K3EXREF option locks the K3's reference oscillator frequency to
> an external 10 MHz source by automatically controlling the REF CAL
> function. While locked to the external source, the K3’s reference
> oscillator frequency is maintained within 2 Hz. Since the K3EXREF
> does not phase lock the K3’s reference oscillator, the external 10
> MHz source has no impact on the K3’s phase noise performance. For
> best performance we recommend your K3 be equipped with the KTCXO3-1
> high stability (0.5 ppm typ.) reference oscillator.
>
>
> 73 from David GM4JJJ
>
>> On 11 Mar 2016, at 16:55, Richard W. Solomon <[hidden email]>
>> wrote:
>>
>> I am a tad confused over this issue. Perhaps I need to read up on
>> how Elecraft controls frequency.
>>
>> My understanding on a "Locked" frequency would infer that the
>> result would be a LOT closer than 2 Hz @ 10 MHz.
>>
>> Is there a detailed description of the process somewhere that I
>> could read ?
>>
>> 73, Dick, W1KSZ
>>
>>
> ______________________________________________________________
> Elecraft mailing list Home:
> http://mailman.qth.net/mailman/listinfo/elecraft Help:
> http://mailman.qth.net/mmfaq.htm Post:
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>

John Severyn

Re: 10 MHz external reference - GPSDO

In reply to this post by GM4JJJ

Thank you David. That article is very good and answered a lot of
questions for me.
73
John AF6QO

On 3/11/2016 8:03 AM, David Anderson wrote:

> You may want to have a look at this for some background on real world frequency stability, and remember that the K3 isn't phase locked to the external reference and is only going to be within 2Hz.
>
> https://www.febo.com/pages/stability/
>
> 73 from David GM4JJJ
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]

GM4JJJ

Re: 10 MHz external reference - GPSDO

In reply to this post by GM4JJJ

Hi Dick,

There may be a little misunderstanding as to what "locked" means in this implementation. It isn't the same as phase locking an oscillator to a high standard reference that's true. On the other hand it is more than good enough for almost any HF application, and it has the huge benefit of not risking degrading the excellent phase noise characteristics of the K3' synthesiser.

Basically any accurate 10 MHz source (calibrated occasionally) that is temperature stable like an ovened crystal oscillator or a Rubidium source could be used for this, however many already have a GPSDO and there are plenty surplus ones as well as fairly inexpensive ones that would be useful for other purposes that can be obtained.

Some people including myself have a thing about frequency accuracy, and it is easy to become over obsessive about it ;-)

I am more concerned with limiting any frequency drift so that narrowband digital modes are not degraded in sensitivity, especially at VHF and above.

73 from David GM4JJJ

> On 11 Mar 2016, at 18:31, Richard W. Solomon <[hidden email]> wrote:
>
> OK, so folks are tossing the term “locked” around without realizing it is wrong.
>
> Then all this talk of using a GPSDO is irrelevant, it will not do any good to use one.
>
> Thanks for the education.
>
> 73, Dick, W1KSZ
>
> From: David Anderson [mailto:[hidden email]]
> Sent: Friday, March 11, 2016 11:07 AM
> To: Richard W. Solomon
> Cc: [hidden email]
> Subject: Re: [Elecraft] 10 MHz external reference - GPSDO
>
> Dick,
>
> I found the reference to that figure I quoted, it is in the K3EXREF manual:
>
> The K3EXREF option locks the K3's reference oscillator frequency to an external 10 MHz source by automatically controlling the REF CAL function. While locked to the external source, the K3’s reference oscillator frequency is maintained within 2 Hz. Since the K3EXREF does not phase lock the K3’s reference oscillator, the external 10 MHz source has no impact on the K3’s phase noise performance. For best performance we recommend your K3 be equipped with the KTCXO3-1 high stability (0.5 ppm typ.) reference oscillator.
>
>
> 73 from David GM4JJJ
>
> On 11 Mar 2016, at 16:55, Richard W. Solomon <[hidden email]> wrote:
>
> I am a tad confused over this issue. Perhaps I need to read up on how
> Elecraft
> controls frequency.
>
> My understanding on a "Locked" frequency would infer that the result would
> be
> a LOT closer than 2 Hz @ 10 MHz.
>
> Is there a detailed description of the process somewhere that I could read ?
>
> 73, Dick, W1KSZ
>

GM4JJJ

Re: 10 MHz external reference - GPSDO

In reply to this post by Joe Subich, W4TV-4

I am not arguing about that calculation Joe, it's proof that you don't need GPSDO accuracy as if will be several orders of magnitude better than that.

73 from David GM4JJJ

> On 11 Mar 2016, at 18:25, Joe Subich, W4TV <[hidden email]> wrote:
>
>
> > While locked to the external source, the K3’s reference
> > oscillator frequency is maintained within 2 Hz.
>
> The K3's reference oscillator is 49.380 MHz (+/-) not 10 MHz.
>
> The K3EXTREF uses the external 10 MHz signal to gate a counter
> which counts the reference. That count is then used to adjust
> the reference frequency. Maintaining the 49.380 MHz reference
> +/- 2Hz is on the order
> of 0.04 ppm.
>
> 73,
>
> ... Joe, W4TV
>
>
>> On 3/11/2016 1:07 PM, David Anderson wrote:
>> Dick,
>>
>> I found the reference to that figure I quoted, it is in the K3EXREF
>> manual:
>>
>> The K3EXREF option locks the K3's reference oscillator frequency to
>> an external 10 MHz source by automatically controlling the REF CAL
>> function. While locked to the external source, the K3’s reference
>> oscillator frequency is maintained within 2 Hz. Since the K3EXREF
>> does not phase lock the K3’s reference oscillator, the external 10
>> MHz source has no impact on the K3’s phase noise performance. For
>> best performance we recommend your K3 be equipped with the KTCXO3-1
>> high stability (0.5 ppm typ.) reference oscillator.
>>
>>
>> 73 from David GM4JJJ
>>
>>> On 11 Mar 2016, at 16:55, Richard W. Solomon <[hidden email]>
>>> wrote:
>>>
>>> I am a tad confused over this issue. Perhaps I need to read up on
>>> how Elecraft controls frequency.
>>>
>>> My understanding on a "Locked" frequency would infer that the
>>> result would be a LOT closer than 2 Hz @ 10 MHz.
>>>
>>> Is there a detailed description of the process somewhere that I
>>> could read ?
>>>
>>> 73, Dick, W1KSZ
>> ______________________________________________________________
>> Elecraft mailing list Home:
>> http://mailman.qth.net/mailman/listinfo/elecraft Help:
>> http://mailman.qth.net/mmfaq.htm Post:
>> mailto:[hidden email]
>>
>> This list hosted by: http://www.qsl.net Please help support this
>> email list: http://www.qsl.net/donate.html Message delivered to
>> [hidden email]
> ______________________________________________________________
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Don Wilhelm-4

Re: 10 MHz external reference - GPSDO

In reply to this post by GM4JJJ

Note that 2 Hz refers only to the reference oscillator which is close to
49,380 kHz. That is about .04 ppm, or about 10 times greater than the
specification for the high stability (optional) TCXO.

The frequency accuracy at HF will also be .04 ppm - at 10 MHz that is
0.4 Hz, at 20 MHzit is 0.8 Hz and so on.

73,
Don W3FPR

On 3/11/2016 11:03 AM, David Anderson wrote:
> You may want to have a look at this for some background on real world frequency stability, and remember that the K3 isn't phase locked to the external reference and is only going to be within 2Hz.
>
>
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Edward R Cole

Re: 10 MHz external reference - GPSDO

In reply to this post by Gary Smith-2

Joe and all interested in the EXREF:

OK ... but most will not measure the 49.380 TCXO
directly*. *though REF CAL displays this.

What I think most want to know is how accurate their operating
frequency will be. I performed rigorous measurements as beta tester
of the EXREF (unfortunately my website was hacked a couple years ago
and I did not recover the beta-testing data page).

First one needs to realize that the TCXO establishes the basic
stability, so choosing the TCXO-3 over the TCXO-1 will provide better
stability and accuracy (these are two different things). I bought
the TCXO-3 with my initial K3/10 purchase so the rest of what I say
is with the better TCXO-3 installed (if frequency is important then
that is first thing I recommend updating).

Mostly, I use 28-MHz as a testing frequency since it is my VHF
transverter IF. On 28-MHz with only the TCXO-3, I see 14-Hz
inaccuracy. This 14/28000000 = 0.5 ppm (I think this is better than
Elecraft specs the TCXO-3). Adding the EXREF I see 2-Hz which is
"about" 0.1ppm. Measurements on 50-MHz are proportional. I see 3-4
Hz accuracy using the EXREF.

So going lower to 10-MHz I measure 1-Hz or less inaccuracy. Due to
the slow drift of the TCXO's, stability is same as accuracy (or maybe
better). So all ham bands lower than 10-MHz show less than 1-Hz
(basically I measure zero error).

Read below for optional background in my measurements-----------
I am measuring with a high-end mw counter able to count up to 26-GHz
and has an internal TCXO reference or can take an external 10-MHz
reference. I also have a LPRO Rubidium source which is rated +/- 5
E-11 stability. I find measurements using either the counter
internal TCXO or the Rb source are identical when measuring under
50-MHz signals (speaks well for that TCXO). I have to wait at least
30-minutes for complete warm-up stabilizing of the Rb source so
usually for normal frequency checks I just run the counter with internal TCXO.

MY station 10-MHz standard is a Russian surplus MV62 Morion OCXO spec
+/-5 E-12 (note it is more stable than my Rb). But the OCXO must be
calibrated as it is voltage tuned. I use the counter/Rb for
that. Long-term (measured in months) stability of my OCXO is only
+/-5 E-5 so I figure that I have to check the OCXO against the Rb
about twice/year (never been more than 1-Hz off in 3-years running).

The counter can only count to 1-Hz so measuring less than a Hz is not
possible. There are sw to make such but I have not gone there (yet).

I build transverters up to 10-GHz which use PLL LO's which actually
lock to the 10-MHz reference. I have noted that I can adjust my OCXO
when measuring 10,224.000,000 MHz to bring it closer to 10-MHz
because any sub-Hz error is multiplied in the mw LO multiplier
chain. Something I cannot do if directly measuring the 10-MHz
reference. Of course this is "nit picking" for setting the OCXO for
use on HF/6m with the K3EXREF.

One caveat in using a Rubidium full time as reference. They have a
finite life-span and more expensive (and probably harder to find once
one fails). So I only run my Rb for high accuracy checks and "lock"
for daily use to my $45 or $25 OCXO. My OCXO runs 24/7 from a 17AH
battery which is float-charged from a good 12v PS.

73, Ed - KL7UW

Date: Fri, 11 Mar 2016 13:25:54 -0500
From: "Joe Subich, W4TV" <[hidden email]>
To: [hidden email]
Subject: Re: [Elecraft] 10 MHz external reference - GPSDO
Message-ID: <[hidden email]>
Content-Type: text/plain; charset=utf-8; format=flowed

> While locked to the external source, the K3?s reference
> oscillator frequency is maintained within 2 Hz.

The K3's reference oscillator is 49.380 MHz (+/-) not 10 MHz.

The K3EXTREF uses the external 10 MHz signal to gate a counter
which counts the reference. That count is then used to adjust
the reference frequency. Maintaining the 49.380 MHz reference
+/- 2Hz is on the order
of 0.04 ppm.

73,

... Joe, W4TV

73, Ed - KL7UW
http://www.kl7uw.com
"Kits made by KL7UW"
Dubus Mag business:
[hidden email]

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Oliver Dröse

Re: 10 MHz external reference - GPSDO

Why would I need the TCXO-3 instead of the TCXO-1 when using the K3EXREF
if the accuracy and stability is provided by the EXREF? Am I overlooking
something here?

Tnx & 73, Olli - DH8BQA

Contest, DX & radio projects: http://www.dh8bqa.de

Am 11.03.2016 um 22:30 schrieb Edward R Cole:

> First one needs to realize that the TCXO establishes the basic
> stability, so choosing the TCXO-3 over the TCXO-1 will provide better
> stability and accuracy (these are two different things). I bought the
> TCXO-3 with my initial K3/10 purchase so the rest of what I say is
> with the better TCXO-3 installed (if frequency is important then that
> is first thing I recommend updating).
>
> Mostly, I use 28-MHz as a testing frequency since it is my VHF
> transverter IF. On 28-MHz with only the TCXO-3, I see 14-Hz
> inaccuracy. This 14/28000000 = 0.5 ppm (I think this is better than
> Elecraft specs the TCXO-3). Adding the EXREF I see 2-Hz which is
> "about" 0.1ppm. Measurements on 50-MHz are proportional. I see 3-4
> Hz accuracy using the EXREF.

GM4JJJ

Re: 10 MHz external reference - GPSDO

Oliver, I was wondering about this, I guess it is just that the short term drift is lower so it won't drift as much between frequency measurement corrections which are made for 1 second every 4 seconds according to some info recently published. I doubt it matters much though. I would be tempted to try it with the standard TCXO first.

Maybe someone from Elecraft would like to comment.

73 from David GM4JJJ

> On 12 Mar 2016, at 07:17, Oliver Dröse <[hidden email]> wrote:
>
> Why would I need the TCXO-3 instead of the TCXO-1 when using the K3EXREF if the accuracy and stability is provided by the EXREF? Am I overlooking something here?
>
> Tnx & 73, Olli - DH8BQA
>
> Contest, DX & radio projects: http://www.dh8bqa.de
>
>
>> Am 11.03.2016 um 22:30 schrieb Edward R Cole:
>> First one needs to realize that the TCXO establishes the basic stability, so choosing the TCXO-3 over the TCXO-1 will provide better stability and accuracy (these are two different things). I bought the TCXO-3 with my initial K3/10 purchase so the rest of what I say is with the better TCXO-3 installed (if frequency is important then that is first thing I recommend updating).
>>
>> Mostly, I use 28-MHz as a testing frequency since it is my VHF transverter IF. On 28-MHz with only the TCXO-3, I see 14-Hz inaccuracy. This 14/28000000 = 0.5 ppm (I think this is better than Elecraft specs the TCXO-3). Adding the EXREF I see 2-Hz which is "about" 0.1ppm. Measurements on 50-MHz are proportional. I see 3-4 Hz accuracy using the EXREF.
>
> ______________________________________________________________
> Elecraft mailing list
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Edward R Cole

Re: 10 MHz external reference - GPSDO

In reply to this post by Gary Smith-2

Olli,

Referring to page 8 in the K3 Owner's Manual (may be a different page
for the K3s):

"Frequency Stability +/- 5 ppm for the TCXO standard; +/- 1ppm for
the optional TCXO."
TCXO-1 and TCXO-3 respectively mentioned above.

ppm means one part per million (1Hz per million Hz which is 1Hz per MHz).
So frequency drift is proportional to the operating frequency.

1ppm at 10-MHz is 10-Hz;1ppm at 28-MHz is 28-Hz
TCXO-1 provides 5ppm (+/- 50 Hz at 10-MHz and +/- 140 Hz at 28-MHz)
TCXO-3 provides 1ppm (+/- 10 Hz at 10-MHz and +/- 28 Hz at 28-MHz)

the basic frequency stability is determined by which TCXO is
installed in your K3.

EXREF "essentially" checks frequency drift of whichever TCXO you have
installed at a fixed time interval of about 4-seconds. It uses a
high stability 10-MHz external signal to compare with the 49.380-MHz
TCXO and corrects the drift that occurs over the 4-second interval.

My measurements of the TCXO-3 show about half the published spec of
1ppm (14 Hz at 28-MHz) and the EXREF limits the drift of the TCXO-3
to about 2 Hz. If I had the TCXO-1 installed, I would expect five
times as much drift.

So which TCXO you install directly impacts frequency stability. The
EXREF reduces that by about an order of five. The EXREF is not the
source of stable LO but merely improves what you have
installed. Does that clear it up?

73, Ed - KL7UW

The question to ask is what amount of frequency stability and
accuracy is important for your type of operations.

Date: Sat, 12 Mar 2016 08:17:32 +0100
From: Oliver Dr?se <[hidden email]>
To: [hidden email]
Subject: Re: [Elecraft] 10 MHz external reference - GPSDO
Message-ID: <[hidden email]>
Content-Type: text/plain; charset=windows-1252; format=flowed

Why would I need the TCXO-3 instead of the TCXO-1 when using the K3EXREF
if the accuracy and stability is provided by the EXREF? Am I overlooking
something here?

Tnx & 73, Olli - DH8BQA

Contest, DX & radio projects: http://www.dh8bqa.de

73, Ed - KL7UW
http://www.kl7uw.com
"Kits made by KL7UW"
Dubus Mag business:
[hidden email]

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Oliver Dröse

Re: 10 MHz external reference - GPSDO

Thanks Ed.

I don't have a problem understanding how the TCXO's work. Maybe I was
not clear enough. ;-) Taking your example from below, having only the
TCXO-1 it is surely *not* drifting 140 Hz at 28 MHz within the 4 or 5
seconds of the EXREF update cycle (same as the TCXO-3 will not drift by
28 Hz in that time), otherwise the K3 would be a *very* crappy radio.
;-) Think you are missing the time domain here. ;-)

So my question still stands: What's the real value of the TCXO-3 over
the TCXO-1 when using the K3EXREF? Unfortunately I do neither have the
measuring equipment to measure below 1 Hz drift (and I'm not seeing that
amount with my TCXO-1 only K3) nor a TCXO-3. So will the radio drift by
0.0014 Hz with the TCXO-1 + K3EXREF within those 4 seconds and the
TCXO-3 will bring it down to 0.00028 Hz? Then I'm probably fine with the
TCXO-1 and even the most sophisticated digital modes available. ;-)

73, Olli - DH8BQA

Contest, DX & radio projects: http://www.dh8bqa.de

Am 13.03.2016 um 04:23 schrieb Edward R Cole:

> Olli,
>
> Referring to page 8 in the K3 Owner's Manual (may be a different page
> for the K3s):
>
> "Frequency Stability +/- 5 ppm for the TCXO standard; +/- 1ppm for
> the optional TCXO."
> TCXO-1 and TCXO-3 respectively mentioned above.
>
> ppm means one part per million (1Hz per million Hz which is 1Hz per MHz).
> So frequency drift is proportional to the operating frequency.
>
> 1ppm at 10-MHz is 10-Hz;1ppm at 28-MHz is 28-Hz
> TCXO-1 provides 5ppm (+/- 50 Hz at 10-MHz and +/- 140 Hz at 28-MHz)
> TCXO-3 provides 1ppm (+/- 10 Hz at 10-MHz and +/- 28 Hz at 28-MHz)
>
> the basic frequency stability is determined by which TCXO is installed
> in your K3.
>
> EXREF "essentially" checks frequency drift of whichever TCXO you have
> installed at a fixed time interval of about 4-seconds. It uses a high
> stability 10-MHz external signal to compare with the 49.380-MHz TCXO
> and corrects the drift that occurs over the 4-second interval.
>
> My measurements of the TCXO-3 show about half the published spec of
> 1ppm (14 Hz at 28-MHz) and the EXREF limits the drift of the TCXO-3 to
> about 2 Hz. If I had the TCXO-1 installed, I would expect five times
> as much drift.
>
> So which TCXO you install directly impacts frequency stability. The
> EXREF reduces that by about an order of five. The EXREF is not the
> source of stable LO but merely improves what you have installed. Does
> that clear it up?
>
> 73, Ed - KL7UW
>
> The question to ask is what amount of frequency stability and accuracy
> is important for your type of operations.
>
> Date: Sat, 12 Mar 2016 08:17:32 +0100
> From: Oliver Dr?se <[hidden email]>
> To: [hidden email]
> Subject: Re: [Elecraft] 10 MHz external reference - GPSDO
> Message-ID: <[hidden email]>
> Content-Type: text/plain; charset=windows-1252; format=flowed
>
> Why would I need the TCXO-3 instead of the TCXO-1 when using the K3EXREF
> if the accuracy and stability is provided by the EXREF? Am I overlooking
> something here?
>
> Tnx & 73, Olli - DH8BQA
>
> Contest, DX & radio projects: http://www.dh8bqa.de
>
>
>
> 73, Ed - KL7UW
> http://www.kl7uw.com
> "Kits made by KL7UW"
> Dubus Mag business:
> [hidden email]
>
> ______________________________________________________________
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>

GM4JJJ

Re: 10 MHz external reference - GPSDO

Hi Oli,

I agree it looks like there is no point in paying for the TCXO-3 if you have a reliable constantly available 10 MHz external reference. Perhaps they recommend the better TCXO as a better fallback if for any reason the external ref is not available, I can't think of any other reason for it.

73 from David GM4JJJ

> On 13 Mar 2016, at 09:27, Oliver Dröse <[hidden email]> wrote:
>
> Thanks Ed.
>
> I don't have a problem understanding how the TCXO's work. Maybe I was not clear enough. ;-) Taking your example from below, having only the TCXO-1 it is surely *not* drifting 140 Hz at 28 MHz within the 4 or 5 seconds of the EXREF update cycle (same as the TCXO-3 will not drift by 28 Hz in that time), otherwise the K3 would be a *very* crappy radio. ;-) Think you are missing the time domain here. ;-)
>
> So my question still stands: What's the real value of the TCXO-3 over the TCXO-1 when using the K3EXREF? Unfortunately I do neither have the measuring equipment to measure below 1 Hz drift (and I'm not seeing that amount with my TCXO-1 only K3) nor a TCXO-3. So will the radio drift by 0.0014 Hz with the TCXO-1 + K3EXREF within those 4 seconds and the TCXO-3 will bring it down to 0.00028 Hz? Then I'm probably fine with the TCXO-1 and even the most sophisticated digital modes available. ;-)
>
> 73, Olli - DH8BQA
>

gm3sek

Re: 10 MHz external reference - GPSDO

In reply to this post by Oliver Dröse

Frequency corrections can only be made in 1Hz steps (at 49.380MHz) and
because the higher-specification TCXO should drift more slowly, fewer
corrections should be required.

But this would only be relevant if someone is using an ultra-narrowband
digital mode that is sensitive to sudden small jumps in frequency.

73 from Ian GM3SEK

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Don Wilhelm-4

Re: 10 MHz external reference - GPSDO

In reply to this post by Oliver Dröse

I think everyone is ignoring something here. What causes the frequency
drift in the first place?
It is temperature changes - the designation TCXO signifies Temperature
Compensated Xtal Oscillator. It is already compensated for temperature.
If the temperature of the TCXO stays the same, the frequency should be
stable.

There will be some frequency change during warmup after power on, and
there will be some frequency change during transmit because the
temperature inside the box will increase, and will cool during periods
of receive.
The difference between the TCXO-1 and the TCXO-3 is one of how much.
The TCXO-3 drift will be smaller than the TCXO-1 over the same
temperature change.

The drift over the 4 or 5 second correction from the external reference
will result in a small correction with either TCXO, but it will be
smaller with the TCXO-3.
Additionally, the frequency drift will be quite small even without the
external reference unless there is a rapid and drastic change in
temperature at the case of the TCXO. These discussions should include
the temperature change during the measurement periods. to complete the
picture.

73,
Don W3FPR

On 3/13/2016 5:27 AM, Oliver Dröse wrote:

> Thanks Ed.
>
> I don't have a problem understanding how the TCXO's work. Maybe I was
> not clear enough. ;-) Taking your example from below, having only the
> TCXO-1 it is surely *not* drifting 140 Hz at 28 MHz within the 4 or 5
> seconds of the EXREF update cycle (same as the TCXO-3 will not drift
> by 28 Hz in that time), otherwise the K3 would be a *very* crappy
> radio. ;-) Think you are missing the time domain here. ;-)
>
> So my question still stands: What's the real value of the TCXO-3 over
> the TCXO-1 when using the K3EXREF?

Edward R Cole

Re: 10 MHz external reference - GPSDO

In reply to this post by Gary Smith-2

Guys<

TCXO's use temperature compensating components to try to keep
frequency stable. They work fairly well if you are at lower
frequencies or not multiplying an LO 18 times. Better is the OCXO
(which uses a heater inside an insulated "oven" to better keep
temperature effects isolated).

The EXREF utilizes the better stability of 10-MHz sources to correct
the drift of the TCXO. I does that at a fixed interval in between
which both TCXO-1 and TCXO-3 will drift. Per Elecraft's
specifications on page 8 the TCXO-3 is 5 times more stable than the
TCXO-1. I have no idea over what time interval the specs are cited,
but most assuredly its more than 4 seconds.

I cannot compare the TXCO-1 as I only have the TCXO-3. Both were
provided long before the EXREF was designed.
I just made a measurement of my K3/10 running 12w for about half a
minute 28.200.000 displayed at 28.200.001 at the start. My REF CAL =
49.380.089 before making the 28-MHz test. After several minute long
tests the frequency has not budged off 28.200.001. REF CAL now is
49.380.095 so the TCXO-3 has moved +6-Hz over about half an hour. I
have been running all afternoon so the K3 was at stable working temp
before I made a measurement.

Unless you are into frequency measuring or run weak signal modes
where hearing a signal is quite difficult, being "on frequency" is
very handy. If running CW you probably have bandwidth cranked down
to 100-Hz. Digital weak-signal modes tolerate even less error. On
2m-eme using JT65, drifting more than +/- 20 Hz will result in the
digital signal failing to decode.

Adding the EXREF improves your K3 by five times so perhaps the TCXO-1
is satisfactory for your operating modes.
My measurements were really accuracy tests and not stability
tests. I did do a 30-minute test at 2m JT65 over a 30-minute period
where I would transmit one minuted continuous and then receive one
minute. MY K3+2m transverter only drifted upward 7-Hz. It was off
frequency by 6-Hz at cold start. K3EXREF with TCXO-3 was used. The
transverter uses a heated 116-MHz overtone xtal oscillator inside an
insulated can.

Does any of this help?
Think I beat this to death - OK?

73, Ed - KL7UW
http://www.kl7uw.com/K3EXREF.htm

Message: 12
Date: Sun, 13 Mar 2016 09:08:10 -0400
From: Don Wilhelm <[hidden email]>
To: Oliver Dr?se <[hidden email]>, [hidden email]
Subject: Re: [Elecraft] 10 MHz external reference - GPSDO
Message-ID: <[hidden email]>
Content-Type: text/plain; charset=windows-1252; format=flowed

I think everyone is ignoring something here. What causes the frequency
drift in the first place?
It is temperature changes - the designation TCXO signifies Temperature
Compensated Xtal Oscillator. It is already compensated for temperature.
If the temperature of the TCXO stays the same, the frequency should be
stable.

There will be some frequency change during warmup after power on, and
there will be some frequency change during transmit because the
temperature inside the box will increase, and will cool during periods
of receive.
The difference between the TCXO-1 and the TCXO-3 is one of how much.
The TCXO-3 drift will be smaller than the TCXO-1 over the same
temperature change.

The drift over the 4 or 5 second correction from the external reference
will result in a small correction with either TCXO, but it will be
smaller with the TCXO-3.
Additionally, the frequency drift will be quite small even without the
external reference unless there is a rapid and drastic change in
temperature at the case of the TCXO. These discussions should include
the temperature change during the measurement periods. to complete the
picture.

73,
Don W3FPR

On 3/13/2016 5:27 AM, Oliver Dr?se wrote:
> Thanks Ed.
>
> I don't have a problem understanding how the TCXO's work. Maybe I was
> not clear enough. ;-) Taking your example from below, having only the
> TCXO-1 it is surely *not* drifting 140 Hz at 28 MHz within the 4 or 5
> seconds of the EXREF update cycle (same as the TCXO-3 will not drift
> by 28 Hz in that time), otherwise the K3 would be a *very* crappy
> radio. ;-) Think you are missing the time domain here. ;-)
>
> So my question still stands: What's the real value of the TCXO-3 over
> the TCXO-1 when using the K3EXREF?

73, Ed - KL7UW
http://www.kl7uw.com
"Kits made by KL7UW"
Dubus Mag business:
[hidden email]

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Gary Smith-2

Re: 10 MHz external reference - GPSDO

Something I have wondered since running MMTTY and looking at the XY
scope is, why do I see the XY ovals shifting clockwise as the station
is transmitting. I find decoding is best when the ovals are as close
to straight vertical & horizontal. If I let them rotate, I lose the
cypher so I have to actively adjust VFO A to maintain their proper
spacing.

I always figured that rotational motion was caused by the time being
shifted as temperatures increase in the TCO ovens and they do resolve
as the radio cools down, only to experience heat and try and resume
with the next transmission.

I see this same effect when in transmit albeit not as bad as some do
on the other end. So my thoughts turn to what mitigates this effect
on my end and I guess it has to be the TCXO crystals and their
stability and its with the looser ones causing the greatest motion
and lack of stability..

I have the higher rated TXCO-3 that supposedly gives basically stable
transmit down to the occasional rated stability at I believe; to
.5ppB, a many times better end at the final result.

So I wonder if in the real world, if my assumptions are correct and
having a decent quality time medium to keep the GPDSO in persistent
good order will keep the twisting of the TY scope bars more secure in
place and better that the find the locations for best reading of the
data?

And further because both rigs are experiencing different temperature
shifts through the messages creation, it requires a greater stability
of both top gave that high quality handshake. to stop this rotation
of the XY coordinates from loosing connection?

I ordered one of the BG7TBL 2015-09-17 Disciplined GPDSO and find it
uses different chips. These give a 5+ at 10x 000 000 000 800 The
earlier on the Morion 201 gave a 1+-deviation at the same range.
miniscule but somethig to consider. I'm hoping if my K3s is attached
to this GPDSO and the ham at the other end is so configured so that
neither unit will have grand shifting and a solid - uninterrupted
signal will be the delightful norm.
t
So I'm hoping this strong desire to tame the K3s rock solid will
result in perfect tight linearity.

I'm looking forward to seeing how well this goes.

73,
Gary
KA1J
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Cortland Richmond-2

Re: 10 MHz external reference - GPSDO

In reply to this post by Gary Smith-2

On 3/13/2016 9:08 AM, Don Wilhelm wrote:
> I think everyone is ignoring something here. What causes the frequency
> drift in the first place?
> It is temperature changes - the designation TCXO signifies

50% OT but...

I'm not complaining about stability, mind; the KX3 temperature
compensation routine works really well, but if I use a GPSDO-clocked
synthesizer to generate my KX3's clock, will that stabilize the on-board
synthesizer? I have a PTS-160.

Cortland Richmond
KA5S
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