[time-nuts] Switching oscillators

J. L. Trantham jltran at att.net
Mon Dec 10 13:18:27 UTC 2012

Not sure why you would want to do this but, if you have a Rb, such as an
LPRO-101 or others, there is a signal that lets you know the Rb is 'locked'.
You could use that to drive a relay that would switch the output of the Rb
to the external input of your device.

This presumes you do not have to mechanically flip a switch on the device to
select internal or external references.

On an OCXO, I guess you could sense the oven current and, when it goes low,
indicating that the oven is 'warm', that could be used to drive the relay to
send the output of the OCXO to the device.  

Otherwise, you would need a 'house standard', that is always on, and measure
how far apart the OCXO is from your 'house standard' and switch when your
OCXO meets certain performance specs.  In that case, why not use the 'house
standard' all the time?  Might be easier to build a battery back-up for your
'house standard'.

Hope this helps.


-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Joseph Gray
Sent: Sunday, December 09, 2012 3:13 PM
To: Discussion of precise time and frequency measurement
Subject: [time-nuts] Switching oscillators

I have a device that has an internal TCXO. I want to feed it with an
external OCXO, but I don't want to completely replace the TCXO.

Here is the scenario. On initial power on, or after a power loss, I want the
internal TCXO to be used. Once the OCXO is up, I want to switch to it. How
could this be done easily and cheaply?

Joe Gray

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