[time-nuts] Re: CTI OSC5A2B02 OXCO testing

[Bart]

Hi fellow time nuts, 

I recently did a design around the CTI OSC5A2B02 

For the tuning voltage I use a LT1029 or LM336 Z5, 5 Volt shunt regulator. Both have a nearly flat tempco. 

I measured the input current of the Vref pin and it is very very low  < 0.1 μA, so I don't expect any trouble using a potentiometer after the shunt regulator as a means for  tuning the OXCO. I used a 25 stroke Bourns trimmer which is no luxere. While calibrating the OSC5A2B02 with a GPSDO and a a good old fashioned analog HP phase meter, I needed to make really tiny shifts with the trimmer to get the OCXO in phase with the GPSDO. I timed it at more than 100 seconds for a whole 360 degree cycle, which is satisfactory for my needs and more or less the accuracy ;limit of this particular OCXO.   

I also did some rudimentary calculations on the heat management of the the two cascaded linear step down voltage convertors I use for the main power supply for the OSC5A2B02 and the shunt regulator. 

You can find the whole story of my design on my Ham Wiki: https://www.pa7elf.nl/en:projects:10_MHz_ocxo_frequency_reference

You can find the schematics @:  https://www.pa7elf.nl/_media/nl:projects:PA7ELF_frequency_reference_with_10_mhz_oven_crystal.pdf

Let me know what you think. 

Bart 
PA7ELF 


> On 4 Jun 2023, at 04:02, Reginald Beardsley via time-nuts <time-nuts at lists.febo.com> wrote:
> 
> 
> 
> That's the spec on the *new* part. These are salvage from decomissioned cell transceivers.They've probably been drifting for 20+ years. Point is they still work. They just need personalized care and feeding.
> 
> The tuning voltage is irrelevant so long as you have a low tempco divider and stable voltage reference to provide that.
> 
> That is the current task, determine what I need for the voltage dividers and order them. $$$ :-(
> 
> Buy some and test them.
> 
> Reg
> 
> 
> 
> 
>     On Saturday, June 3, 2023 at 08:46:36 PM CDT, Bob Camp via time-nuts <time-nuts at lists.febo.com> wrote:  
> 
> Hi
> 
> Per the published spec on the part, it should hit 10 MHz at 2.0 V. 
> 
> A properly working part should move 5 to 10 Hz for a half volt change
> (like the one from 1.9942 to 2.6832 V. 
> 
> With any OCXO, meaningful data can only be taken after the part has
> warmed up. For accurate data, something like a 24 hour warmup is 
> a pretty good idea.
> 
> Bob
> 
>> On Jun 3, 2023, at 4:40 PM, Reginald Beardsley via time-nuts <time-nuts at lists.febo.com> wrote:
>> 
>> 
>> Here are the results of my preliminary test using just a bench supply and 5386A on the internal XOCO. I just adjusted the Vref until I got within 1 Hz. PSU is settable in 10 mV steps. Data are from my 34401A.
>> 
>> Vref MHz
>> 
>> 1.5819 10.000000??
>> 
>> 1.7758 10.00000015
>> 
>> 1.6924 10.00000010
>> 
>> 1.7740 10.00000050
>> 
>> 2.0853 10.00000047
>> 
>> 1.9374 10.00000040
>> 
>> 2.1520 10.00000075
>> 
>> 23708 10.00000073
>> 
>> 1.9942 10.00000046
>> 
>> 2.6832 10.00000065
>> 
>> _______________________________________________
>> time-nuts mailing list -- time-nuts at lists.febo.com
>> To unsubscribe send an email to time-nuts-leave at lists.febo.com
> _______________________________________________
> time-nuts mailing list -- time-nuts at lists.febo.com
> To unsubscribe send an email to time-nuts-leave at lists.febo.com
> 
> _______________________________________________
> time-nuts mailing list -- time-nuts at lists.febo.com
> To unsubscribe send an email to time-nuts-leave at lists.febo.com