[Elecraft] 10 MHz external reference - GPSDO

[Oliver Dröse]

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 <droese at necg.de>
> To: elecraft at mailman.qth.net
> Subject: Re: [Elecraft] 10 MHz external reference - GPSDO
> Message-ID: <56E3C28C.90803 at necg.de>
> 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:
>     dubususa at gmail.com
>
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