[time-nuts] 10MHz to 25MHz

Bob Camp kb8tq at n1k.org
Sat Jan 21 11:52:11 EST 2017


> On Jan 21, 2017, at 10:25 AM, jimlux <jimlux at earthlink.net> wrote:
> On 1/20/17 7:10 PM, Bob Camp wrote:
>> Hi
>> There are several other materials that you can make crystal resonators out of that
>> are piezo electric. Some of them can give you much higher Q. This comes with a whole
>> raft of other issues. Langesite is one of the more common materials you see people
>> playing with. It is common enough that I’ve actually played with it myself.  The simple
>> answer is that when you look at cost, Q, and stability (aging, ADEV, temperature) —
>> it is tough to beat quartz. If you have a few hundred thousand dollars, you can play
>> with great big chunks of Sapphire. Toss in a bit of this and a bit of that and you can get a
>> pretty amazing oscillator. That device may (or may not) be < $1,000,000 depending
>> on how you do the accounting and how many parts you spread the costs over.
> would not a true time nut grow their own sapphire?

Or at the very least spend some quality time digging a 100 lb lump up out 
of the Australian outback ….

> Realistically, isn't it all about the crystal lattice.. SiO2 vs Al2O3 vs Lanthanum Gallium Silicate vs Lithium Niobate
> WHat makes a "good" material?  I would think the ability to grow a very uniform crystal is part of it, but are certain crystal forms better than others?

Indeed you need a “well grown” crystal and figuring out how to grow 
them without adding a bunch of stress, contamination, and imperfections
in the lattice is a very big deal. Past that, for Q you get into the acoustic 
loss properties of the material. Some materials are less lossy than others. 
It is no different than picking a microwave dielectric in that regard. Some 
of the fun and games involved is measuring the acoustic properties of
all these materials. 


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