OCXO OSC5A2B02 10.000 MHZ


Alan Jones
 

I finally received a OCXO from the extremely slow boat from China.
How much resistance do I need in order to adjust "Vcont" on pin #3 ?

My initial hook up without Vcont, according to my eBay 8 digit frequency counter showed a slow frequency drift from about 9.999.820 MHz up to 10.000.027 and stabilized after about 7 minutes. Current draw got up to a max of around 400 mA and then settled in around 198 mA and the oscillator can was warm to the touch.

The OCXO I received from eBay was used and has a calibration sticker on it.

While looking for info on this OCXO I stumbled onto this document about Precision Oscillator Overview.
http://freqelec.com/oscillators/osc_overview_4-07.pdf

I just ordered the GPSDO that Chuck referenced in an earlier email.
We will see how long it takes to get here!

Al, N8WQ


Graham, VE3GTC
 

Al,

Your brief description of the operation of your OCXO sounds like a
typical OCXO - higher current at start up til stabilization, then lower
current draw. Same goes for the frequency drift.

The adjustment only needs a potentiometer to be used as a voltage divider
and is not overly critical as far as value is concerned. I tend to use
something around 5k.

There is often a Vref output from OCXO that you would use on one side of
the pot rather than the VCC, the other side of the pot to ground, and
the wiper to the ADJ.

Don't expect a lot of adjustment range, on the order of single digit Hz
+/- of the nominal frequency

cheers, Graham ve3gtc

On 9/24/2018, "Alan Jones" <oalanjones@gmail.com> wrote:

I finally received a OCXO from the extremely slow boat from China.
How much resistance do I need in order to adjust "Vcont" on pin #3 ?

My initial hook up without Vcont, according to my eBay 8 digit frequency
counter showed a slow frequency drift from about 9.999.820 MHz up to
10.000.027 and stabilized after about 7 minutes. Current draw got up to a
max of around 400 mA and then settled in around 198 mA and the oscillator
can was warm to the touch.

The OCXO I received from eBay was used and has a calibration sticker on it.

While looking for info on this OCXO I stumbled onto this document about
Precision Oscillator Overview.
http://freqelec.com/oscillators/osc_overview_4-07.pdf

I just ordered the GPSDO that Chuck referenced in an earlier email.
We will see how long it takes to get here!

Al, N8WQ


Alan Jones
 

Hi Graham,
Thanks for confirming the operation of the OCXO.
How critical is 5 volt precision in using the OCXO?

Al

On Mon, 24 Sep 2018 10:16:38 -0400, Graham <planophore@aei.ca> wrote:

Al,

Your brief description of the operation of your OCXO sounds like a
typical OCXO - higher current at start up til stabilization, then lower
current draw. Same goes for the frequency drift.

The adjustment only needs a potentiometer to be used as a voltage divider
and is not overly critical as far as value is concerned. I tend to use
something around 5k.

There is often a Vref output from OCXO that you would use on one side of
the pot rather than the VCC, the other side of the pot to ground, and
the wiper to the ADJ.

Don't expect a lot of adjustment range, on the order of single digit Hz
+/- of the nominal frequency

cheers, Graham ve3gtc


On 9/24/2018, "Alan Jones" <oalanjones@gmail.com> wrote:

I finally received a OCXO from the extremely slow boat from China.
How much resistance do I need in order to adjust "Vcont" on pin #3 ?

My initial hook up without Vcont, according to my eBay 8 digit frequency
counter showed a slow frequency drift from about 9.999.820 MHz up to
10.000.027 and stabilized after about 7 minutes. Current draw got up to a
max of around 400 mA and then settled in around 198 mA and the oscillator
can was warm to the touch.

The OCXO I received from eBay was used and has a calibration sticker on it.

While looking for info on this OCXO I stumbled onto this document about
Precision Oscillator Overview.
http://freqelec.com/oscillators/osc_overview_4-07.pdf

I just ordered the GPSDO that Chuck referenced in an earlier email.
We will see how long it takes to get here!

Al, N8WQ


Ray
 

I purchased this one:
https://www.ebay.com/itm/1-USED-CETC-CTI-OSC5A2B02-10MHz-5V-26-26-12-Square-Wave-OCXO-Crystal-Oscillator/332389156868?hash=item4d63f00804:g:5VIAAOSwruVZxm6k

I took a 5K pot, connected high side to +5V, low side to GND, wiper to the control pin. I let the OXCO warm up for a couple of hours. Using a rubidium standard, I calibrated my frequency counter to 10.000000 MHz. I then connected the OCXO to the counter and adjusted the pot to 10.000000 MHz. I initially tried a 10K pot but it was critical to adjust which is why I went to 5K.

I could have used my scope in XY mode like Chuck does, but it is packed away and I didn't want to dig it out.

Ray,
AB7HE


Graham, VE3GTC
 

Good question and my best answer is that it depends on the particalar
device and whether there is an internal regulator (i.e. 5v to 3.3V or
similar) and how good that internal regulator is.

I found some data for this device:

http://www.cti.ac.cn/Products/system/Professional/crystal/2013/0725/289.html

Use google translate.

Power is spec'ed at 5.0V +/- 5% and control V range as 2.0V +/- 2.0V
(that is 2v nominal with a range of + and - 2v from nominal i.e. 0 to +4
)

Like all precision devices, the better regulation the better the results.
Any noise or irregularities in the supply could result in excessive
phase noise and variations in your reference.

cheers, Graham ve3gtc

On 9/24/2018, "Alan Jones" <oalanjones@gmail.com> wrote:

Hi Graham,
Thanks for confirming the operation of the OCXO.
How critical is 5 volt precision in using the OCXO?

Al

On Mon, 24 Sep 2018 10:16:38 -0400, Graham <planophore@aei.ca> wrote:

Al,

Your brief description of the operation of your OCXO sounds like a
typical OCXO - higher current at start up til stabilization, then lower
current draw. Same goes for the frequency drift.

The adjustment only needs a potentiometer to be used as a voltage divider
and is not overly critical as far as value is concerned. I tend to use
something around 5k.

There is often a Vref output from OCXO that you would use on one side of
the pot rather than the VCC, the other side of the pot to ground, and
the wiper to the ADJ.

Don't expect a lot of adjustment range, on the order of single digit Hz
+/- of the nominal frequency

cheers, Graham ve3gtc


On 9/24/2018, "Alan Jones" <oalanjones@gmail.com> wrote:

I finally received a OCXO from the extremely slow boat from China.
How much resistance do I need in order to adjust "Vcont" on pin #3 ?

My initial hook up without Vcont, according to my eBay 8 digit frequency
counter showed a slow frequency drift from about 9.999.820 MHz up to
10.000.027 and stabilized after about 7 minutes. Current draw got up to
a
max of around 400 mA and then settled in around 198 mA and the
oscillator
can was warm to the touch.

The OCXO I received from eBay was used and has a calibration sticker on
it.

While looking for info on this OCXO I stumbled onto this document about
Precision Oscillator Overview.
http://freqelec.com/oscillators/osc_overview_4-07.pdf

I just ordered the GPSDO that Chuck referenced in an earlier email.
We will see how long it takes to get here!

Al, N8WQ