Re: Frequency reference for the K3 directly off a GPS

Posted by Matt Zilmer-3 on Aug 13, 2015; 1:59pm
URL: http://elecraft.85.s1.nabble.com/Frequency-reference-for-the-K3-directly-off-a-GPS-tp7606275p7606276.html

Hi Sverre,

This type of 10 MHz output has short term stability problems and isn't
suitable for direct drive of a K3 (imho).  It *could* be used, if
integrated over a long time constant (thinking many seconds) to drive
a D.O., but that would take additional circuitry.  It might be quite a
project.  

You're probably better off with A GPSDO or a Rubidium source.  Even a
plain OCXO would work if you can keep it calibrated.

73,
matt
W6NIA

On Thu, 13 Aug 2015 06:36:31 -0700 (MST), you wrote:

>Some recent GPS modules (ublox Neo 7) have a programmable output that in
>addition to the 1 pps output can be programmed even to output 10 MHz. This
>output has a lot of jitter as it seems to be derived from a 48 MHz clock
>which is divided down in such a way as to generate a mix of short and long
>cycles but so that the average frequency is maintained accurately at 10 MHz.
>
>A description can be found here
>https://sites.google.com/site/g4zfqradio/u-blox_neo-6-7 and performance is
>partly described here:
>https://www.febo.com/pipermail/time-nuts/2014-August/086257.html
>
>My question is regarding the K3 external reference input. Is this source
>good enough to drive the K3 reference? Can the K3 clean up the jitter
>internally, or does the K3 require a source with much less phase noise?
>
>
>
>
>-----
>Sverre, LA3ZA
>
>K2 #2198, K3 #3391,
>LA3ZA Blog: http://la3za.blogspot.com,
>LA3ZA Unofficial Guide to K2 modifications: http://la3za.blogspot.com/p/la3za-unofficial-guide-to-elecraft-k2.html

Matt Zilmer, W6NIA
--
"Always store beer in a dark place."  -R. Heinlein

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