One thing I've seen on several OCXO and small Rbs is that the EFC pin is
internally wired in the middle of a voltage divider using two fairly
high value (>10K) resistors between Vref and ground. That ties the
varactor to the middle of the EFC range when no external tuning is
required. For external tuning, put the EFC pin on the wiper of a pot
between the Vref pin and ground that has a much lower value than the
internal divider. That stiffer voltage will override the internal divider.
John
----
On 12/23/21 12:51 PM, Andy Talbot wrote:
I've always assumed this is because they need to know the reference is
clean and under the OCXO manufacturer's control if it's to meet specs. If
the user had to supply the reference there's no knowing how clean it is.
Andy
www.g4jnt.com
On Thu, 23 Dec 2021 at 17:47, Attila Kinali <[email protected]> wrote:
On Thu, 23 Dec 2021 14:42:27 +0100
Wilko Bulte <[email protected]> wrote:
A quick experiment learned that the OCXO freq responds to the EFC
voltage.
So, looks like the Vref circuit in the OCXO has died.
A stupid side question: Why do have OCXO a Vref output in the
first place?
I can see that some form of reference might make stabilizing
the power in the crystal easier, but that still wouldn't make
it necessary to have an actual reference output.
And related to that: Would supplying the voltage reference
externally, in case of a broken Vref output, work for whatever
is inside that needs this reference voltage?
Attila Kinali
--
The driving force behind research is the question: "Why?"
There are things we don't understand and things we always
wonder about. And that's why we do research.
-- Kobayashi Makoto
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