[time-nuts] TCXO improvement

[Bob kb8tq]

Hi

There are a lot of dewar / vacuum flasks on eBay in a wide variety of 
shapes and sizes. Some get into the proper combination of affordability,
size and shape. There does not appear to be a constant supply of any
one version so it is very much shop and see.

Dewar based OCXO’s go way back ( in this case that’s into the 1950’s :) ). 
They are still made today in very limited quantities. Heat flow is highly 
asymmetric so it is a somewhat different design approach than a “normal”
oven. 

Heating a TCXO is generally a bad idea. You get the low circuit Q / poor ADEV
of the TCXO and the warmup time and complexity of an OCXO. Yes, there are
some fairly unusual TCXO’s that do pretty well on ADEV. They aren’t what 
you are going to buy at DIgikey. 

Bob

> On Aug 2, 2019, at 4:18 AM, Bill Slade <slade_bill at hotmail.com> wrote:
> 
> Hello!
> I have done this and can attest that it works well.  I did not use a TCXO, though.  I used a 48 MHz, third-overtone AT-cut crystal in a Colpitts oscillator configuration.  The vacuum flask was ovenized to maintain temperature near the stationary point of the temp characteristic (near 50 deg C).   The oscillator could be phase locked to an external atomic reference (in our case, a rubidium) or 10 MHz from a GPS receiver.
> 
> The inspiration was a couple of excellent NASA reports from some years ago, which I have attached (as links because files are large) for convenience.
> Cheers,
> Bill
> Nasa Precision Quartz 1<https://onedrive.live.com/embed?cid=3CBCA1CF8AB21FE1&resid=3CBCA1CF8AB21FE1%213504&authkey=AA4EqyT05-Iz2nU&em=2>
> Nasa Precision Quartz 2<https://onedrive.live.com/embed?cid=3CBCA1CF8AB21FE1&resid=3CBCA1CF8AB21FE1%213505&authkey=AEG_NqxtMFVIE_o&em=2>
> 
> On 02/08/19 01:35, Perry Sandeen via time-nuts wrote:
> 
> Yo Bubba Dudes!,
> If one has the space, a simple cure might be to get one of the wide mouth thermos containers that they sell in large variety stores such as Wal-Mart for being able to eat something like stew or some semi-solid hot food out of the container itself.
> Regards,
> Perrier
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