[time-nuts] VC-OCXO EFC stability.

[Bob Camp]

Hi

If you find that your EFC port is low impedance - check it for a bias voltage. It may well have a pull up resistor to an internal Vref. The intent is that you simply tune it with a resistance to ground. 

Bob

> On Jan 6, 2015, at 8:49 PM, Daniel Mendes <dmendesf at gmail.com> wrote:
> 
> 
> I tried something like that once just to discover that the OCXO VFC port had low impedance, so my voltage divider didn´t behave very well. So i put an amp op in unitary gain configuration between the two and things improved a lot. Then I changed the amp op for a DP precision part and things improved again. Then I choose resistors/trim pot with low TCR for the voltage divider and things improved again. Then I made a good layout, termally coupling the resistors.... well, you see this has no end :)
> 
> Daniel
> 
> On 06/01/2015 22:40, ct1dmk wrote:
>> Hi,
>> 
>> With a multiturn pot and a 78L05 I can get a 0 to 5V EFC to tune
>> an OCXO on desired freq. But... maybe other voltage regulators
>> or other scheme have better temp stability than the old 78L05.
>> 
>> Before I crawl lost in new'ish fancy regulator land does anybody
>> know the killer solution/IC for this job ?
>> 
>> Luis Cupido
>> ct1dmk.
>> 
>> 
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