Used OCXO or New TCXO ?

[wp100]

Hi,

Looking for a better oscillator for experimentation /reference etc on a budget so a new OCXO is not realistic.

Have seen these ' Used but working' ones on Ebay but do wonder what their actual specification will really be like after so many year of use ?
**broken link removed**

For the same money I could get a New TCXO which has 0.5ppm
However seen very little about them and cannot establish how the control voltage pin should be connected, or not, if temperature compensation is not used ?
https://www.farnell.com/datasheets/1698631.pdf

Any suggestions welcome..

 

[davenn]

in the second one, you need to connect the control voltage, else the freq will drift ( that is ... you cannot leave it floating)
so depending in the freq you want out of the unit you select the appropriate voltage.
It MUST be very clean and stable

Dave

 

[biff44]

if I were looking for a low cost very accurate oscillator, I would get a gps disciplined oscillator on ebay. They have a low noise crystal oscillator that uses a gps receiver to correct small frequency drifts. hp, symmetricon, fei, thunderbolt. maybe $150

 

[davenn]

if I were looking for a low cost very accurate oscillator, I would get a gps disciplined oscillator on ebay. They have a low noise crystal oscillator that uses a gps receiver to correct small frequency drifts. hp, symmetricon, fei, thunderbolt. maybe $150

Agreed

either that or a Rubidium standard off ebay they are also going for very affordable prices, often less that $100. I had great success using it as the 10MHz ref for my PLL for my 24GHz transceiver

cheers
Dave

 

[biff44]

Rubidium is certainly STABLE. But it might not be accurate...you would need to calibrate it somehow to get it dead-on frequency.

Also, the rubidium physics package have a limited lifetime. It's basically a rubidium lamp and a rubidium filter cell, and can burn out. If I got one, I would look for one that was "new old stock", not one that was pulled from years of use in a cell tower, or a wicked old HP one from a lab reference."

There is no such thing as a "rubidium oscillator". Its a crystal oscillator that is multiplied up to the rubidium microwave resonance frequency. The microwave energy is focused on the rubidium filter cell, and if the frequency is just right, the light gets attenuated. They dither the frequency +/- a little, and try to "frequency lock" the XTAL frequency to the point of minimum light transfer. Being a "frequency locked loop", it is subject to slight frequency drifts (unlike a PLL).

 

[wp100]

Hi,

Purchased this unused but old stock 13mhz OCXO from abroad which was connected up as per the datasheet the seller supplied.

However instead of the expected heater current it just used 3.5ma, so believed the heater was shot, though the scope showed a decent enough 13mhz signal.

Assuming it was just acting a a simple oscillator decided to take a look inside and below is what I found.

It looks like a crystal stuck on top of a 28pin smd ic , but nothing I would have thought was acting as a heating chamber, partic with the crystal (?) being pressed hard against the cans metalwork.

Can anyone say if it actually is an OCXO ? - with that low current wondered if it was and early version of a TCXO ?

 

[rfmw]

What is the manufacturer and the OCXO model number from the photos you have attached?

 

[wp100]

Hi,

This is the actual device , the description /code the seller gave and the datasheet they specified.

Was suspicious about the different coding on the can but they were supposed to be credible seller.

13 MHz OCXO Frequency Oscillator by C-MAC, HCMOS Output, CFPO-5A1-36-5V-13MHz