[time-nuts] Has anybody checked this? GPSDO in kit

Attila Kinali attila at kinali.ch
Sat Oct 22 20:18:27 EDT 2016

On Sat, 22 Oct 2016 10:34:53 -0400
Tim Shoppa <tshoppa at gmail.com> wrote:

> I just went and visited their website, and see they also offer a "kit OCXO"
> from mostly through-hole parts and PCB. The OCXO insulation box is made out
> of PCB, the thermostat is simply a jellybean TO92 transistor, and the 27MHz
> crystal is an AT-cut being operated around 45C, so nothing awful
> time-nutty, but still pretty neat that it's a kit. Details at
> http://qrp-labs.com/images/ocxokit/ocxosynth_assembly.pdf
> show that it walks about 14ppm during warmup and then might be good to a
> ppm or so.

It's funny how you can tell from the transistors used, where the designer
is from (BC547 -> European :-)

Kits like these have been around ever since I remember. This is one of
the better ones, where the crytal isn't just soldered to some transistor,
but a whole "insulation box" built around it. In german we call these
things "Quarzofen" (lit. "quartz oven") and that's IMHO a very precise
description what they are :-)

Generally it's not very difficult to build some kind of temperature
stabilization system. Heck, just using a heater transistor with a
constant current through it will give you a more stable temperature,
even if you don't control the current other than keeping it constant.
Puting some form of box around it that restricts air and thus heat flow
will make it even better. Using some temperature control and you are
within 1-2°C of stability and way better than most hams need.

The difficulty starts when you need more than that, when you need
temperature stabilities below 1°C, when you want to keep it stable
to 1mK or even below that.

BTW: If anyone has recomended texts on how to build stable ovens
for crystals, I'd like to hear about them. I've alread had a look
at what Rick Karlquist wrote, but I would also like to read more.
Unfortunately, good stuff literature is, as often, hard to find.

On Sat, 22 Oct 2016 17:04:19 -0400
"William H. Fite" <omniryx at gmail.com> wrote:

> You need to catch up on what hams are REALLY using.
What hams have been using varies a lot. As much as what time-nuts are using,
or probably even more. I know a few people who still build valve PAs because
they are "indestructible" (aka can take a lot of abuse without damage).
But I also know people who do designs that are at the border of what
is technically possible today.

				Attila Kinali

Malek's Law:
        Any simple idea will be worded in the most complicated way.

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