[time-nuts] Practical considerations making a lab standard with an LTE lite

Bob Camp kb8tq at n1k.org
Sun Nov 23 17:45:25 EST 2014


A lot of these parts are designed for use in a system environment rather than sitting out on a bench. That’s as true of the KS boxes (forced air cooling) as it is of the LTE’s. In > 90% (and likely  > 99.9%) of the places a TCXO gets used, it’s packed tight in with a bunch of other stuff. Not only is there no air movement, there might not be much air. A cell phone is a good example of this sort of assembly. Other battery powered portable gear fit this same general model, but possibly not to the same degree of “cram it in". 

Yes, we love our big rack mounted boxes full of this or that. They are useful. The TCXO guys would go broke quickly if that was the market they focused their main efforts on. Big Morion 2” x 2” x 1” OCXO’s, yes those are targeted more at big rack mount this or that. Different market focus for different products. It’s not a one size fits all world. 

Indeed, adapting a TCXO to a bench environment is something that you need to do. A nice fluffy cotton towel works quite well. Yes, that’s a 1970’s solution to the problem.  Most TCXO’s were bigger back then. The issue has been around “for a while”. It’s actually not a bad thing to keep handy when testing OCXO’s. If they don’t work you can always use it to cry into …:)

> On Nov 23, 2014, at 11:24 AM, Tom Van Baak <tvb at LeapSecond.com> wrote:
> The short-term performance is 10x worse if you don't shield the TCXO from air, even if the ambient air is "still". I suggested Said sell the product with some sort of engineered shield in place. Instead each of us will solve the problem in our own way; which is ok for a dev kit.
> For plots and photos showing performance with, and without, and with insulation see:
> http://leapsecond.com/pages/LTE-Lite/
> The difference is dramatic, especially if you are used to working with OCXO where this sort of effect does not occur.
> The insulation may be found in convenient rolls at many local stores. I used TP, which for this application is an acronym for Thermal Paper.
> /tvb
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