When I designed the HP E1938A, I put a 2.5V reference IC inside the oven
and brought out both terminals of it. This was intended to provide a
reference voltage to the external DAC that generated the tuning voltage
for the loop that locked it loosely to GPS. It had its own return path
that
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
Hi:
I'd second this. When I was working at HP on the Kobe Instrument Division products (component testers) the 4352S VCO
tester had a very special power supply for the tuning voltage that was extremely clean so as not to detract from the VCO
under test.
--
Have Fun,
Brooke Clarke, N6GCE
> On 23 Dec 2021, at 18:58, Attila Kinali wrote:
>
> On Thu, 23 Dec 2021 12:14:48 -0500
> Bob kb8tq wrote:
>
>> It’s a pretty good bet that the Vref is 5V
>
> A quick google lead me to this forum post:
>
> On 23 Dec 2021, at 18:47, Attila Kinali wrote:
>
> On Thu, 23 Dec 2021 14:42:27 +0100
> Wilko Bulte 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
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 wrote:
>
Plus it was temperature stabilised since it was in the oven area.
Regards
Paul
WB8TSL
On Thu, Dec 23, 2021 at 2:16 PM ed breya wrote:
> Many of the older VTOCXOs have the internal reference voltage accessible
> simply to use them stand-alone. A remote adjustment pot could be fed
> from the
Many of the older VTOCXOs have the internal reference voltage accessible
simply to use them stand-alone. A remote adjustment pot could be fed
from the reference, and set the fine tuning voltage, without needing any
other support from the system. Nowadays we typically tune from PLLs, and
such,
Hi
The main reason OCXO’s have a Vref is that an ovenized
voltage source is likely to be more stable over temperature
than what you can easily buy and mount on a PCB.
The gotcha is the common ground found on most OCXO’s.
Putting the oven current through that ground makes keeping
the Vref (and
On Thu, 23 Dec 2021 18:57:10 +0100
Attila Kinali wrote:
> On Thu, 23 Dec 2021 12:14:48 -0500
> Bob kb8tq wrote:
>
> > It’s a pretty good bet that the Vref is 5V
>
> A quick google lead me to this forum post:
>
On Thu, 23 Dec 2021 12:14:48 -0500
Bob kb8tq wrote:
> It’s a pretty good bet that the Vref is 5V
A quick google lead me to this forum post:
https://www.eevblog.com/forum/projects/a-look-at-my-symmetricom-gpsdo-(ocxo-furuno-receiver)/1325/
Looks like the Vref is supposed to be 2.5V
On Thu, 23 Dec 2021 14:42:27 +0100
Wilko Bulte 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
Hi
It’s a pretty good bet that the Vref is 5V
Bob
> On Dec 23, 2021, at 8:42 AM, Wilko Bulte wrote:
>
> hi,
>
> I am currently trying to revive a Trimble UCCM-LPS ex-telco GPSDO.
> The model is a 57963-D according to the PCB silkscreen.
>
> Got the board without its OCXO but luckily my
hi,
I am currently trying to revive a Trimble UCCM-LPS ex-telco GPSDO.
The model is a 57963-D according to the PCB silkscreen.
Got the board without its OCXO but luckily my stash of surplus I have
discovered a Trimble OCXO labeled 72345-86. Given that that OCXO also has a
label UCCM-LPS it
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