[time-nuts] OCXO settling my goals What I do have

Thu Sep 15 01:03:52 UTC 2011

Paul,

As far as shop temperature, I don't think you will have much of a problem,
if it only varies a few degrees +/- over the day. The concern would be if it
got as hot as, or hotter than, the oven temp, which is around 100+ degrees
F., as it's set according to the manufacturer of the OCXO.

What most do, is they mount a thermistor close to the crystal, inside the
same cavity, and that in turn operates the power source for the heater. The
thermistor is the thermostat, and it controls a variable DC supply that
feeds a strip heater surrounding the crystal.

As far as drift after being turned off, I think that has more to do with how
new, or how aged the OCXO is, in how quick it will settle again. I would say
a new unit might have to be left on for some time before it settles, but an
aged one not near as long. A quick check of a frequency counter over a day,
or several, would tell you, and then you can see when it settles back to the
correct value, and starts to stay there over time.

Someone mentioned Dewar flasks earlier, and I am experimenting with them
now. I couldn't find any old wide mouthed flasks, so I bought a large
Thermos brand, (for coffee), and made a narrow board that will fit through
the neck. I have a standard cell that uses a large one, except it has a
glass cork that is evacuated, and the Thermos has a plastic one filled with
insulation, so I don't know how well it will work. Anyhow, these will help
when they are powered down, such as a power failure, as the temperature
takes some time to drop off. I'm actually designing a voltage reference
inside this one.

Will

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com]On
Behalf Of Paul A. Cianciolo
Sent: Wednesday, September 14, 2011 8:34 PM
To: 'Discussion of precise time and frequency measurement'
Subject: Re: [time-nuts] OCXO settling my goals What I do have

I forgot to mention.

I do  have data for following.

The Rakon OCXO
The Spectracom 8165 WWVB  Disciplined Oscillator
Ball-Efratom Rubidium  Telco version

24 hours worth of data  at 10 Mhz  using the Z3801A  1PPS output for the
start channel
Same 24 begin and end times

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Paul A. Cianciolo
Sent: Wednesday, September 14, 2011 8:23 PM
To: 'Discussion of precise time and frequency measurement'
Subject: Re: [time-nuts] OCXO settling my goals

Murray,

You hit the nail right on the head.  Thank you for pointing this out.

I don't truly know what I want to accomplish, and without defining that, how
can you define what testing needs to be done.
Here are some facts.

1) I am absolutely intrigued, addicted, to the concept of precision
oscillators, I find them very exciting.
2) I don't even know enough about the topic to understand how much I don't
know.
3) I would like to try to optimize a given OCXO by adjusting variables, EFC
voltage quality, Oven voltage quality, the environment where the OCXO
resides, additional insulation etc.
4) TimeLab is a great tool but there is so much about I do not understand
yet.
5) I have at my disposal several Telco Rubidiums, a number of OCXO's  a
Z3801A, several WWVB Locked oscillators, TimeLab and a working HP5370B
6) I need a concrete platform to stand on a starting point to reference back
to.
7) I do not have a climate controlled lab.

There seems to many variables to which I have not answers.
Without the basic foundation, I am only making guesses and not well educated
ones either.

Assumptions:

1) The Z3801 is likely to be the best reference source I can afford.
2) Temperature control of the oscillator is the greatest variable for a
crystal oscillator,
3) All of these items, EFC voltage quality, Oven voltage quality, the
environment where the OCXO resides, additional insulation etc. have varying
degrees of effect  on a given oscillators performance.
I use the broad term performance to cover the fact that I don't yet have a
comprehensive list of the oscillator's parameters.
4) A good place to start would be to study data sheets, find out what is
important to manufacturers, thereby seeing what's important to OEM using
these OXCO.

For those of you who are Hams this topic is very similar to a question that
is frequently asked of me and other hams..  What's the best antenna?
It depends; there are too many variables to list, with various weighting
factors, that are dependent on an entirely different set of variables.
Here in lies the rub

Maybe it time for me to listen more, and ask fewer questions.

Sorry for the long post.

Paul A. Cianciolo
W1VLF
http://www.rescueelectronics.com/
Our business computer network is  powered exclusively by solar and wind
power.
Converting Photons to Electrons for over 20 years

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Hal Murray
Sent: Wednesday, September 14, 2011 5:57 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] OCXO settling

> Maybe 2 days would be a good compromise?

I don't think you are going to get a solid answer, especially since you
haven't mentioned how good of a result you want or need.

How about recording some data and telling us what happens?

--
These are my opinions, not necessarily my employer's.  I hate spam.

_______________________________________________
time-nuts mailing list -- time-nuts at febo.com To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

_______________________________________________
time-nuts mailing list -- time-nuts at febo.com
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

__________ Information from ESET Smart Security, version of virus signature
database 5851 (20110206) __________

The message was checked by ESET Smart Security.

http://www.eset.com