[time-nuts] The 5MHz Sweet Spot

Bob Camp lists at rtty.us
Sat Nov 2 01:07:46 EDT 2013


Hi

The real answer is that nobody knows. The economics essentially make finding out very expensive. Q most certainly goes up, I don’t think anybody disputes that. The questions about flicker / ADEV all revolve around small blank parts with major edge sensitivity issues. They also probably were not running in a very good oven. Unless somebody with very deep pockets decides they need to find out, it’s going to be an un-answered question. 

Bob


On Nov 1, 2013, at 11:41 PM, Richard (Rick) Karlquist <richard at karlquist.com> wrote:

> 
> 
> On 11/1/2013 8:28 PM, Bob Camp wrote:
>> HI
>> 
>> If you doubled the diameter of the blank each time you cut the frequency in half, all sorts of nice things might happen. If you start with a 1/2” blank in at 10 MHz that goes to 1” at 5 MHz and 2” at 2.5 MHz. Around 1 MHz you would get to a 5” blank.
>> 
>> Good luck finding high grade quartz bars to cut 5” (or even 1”) blanks out of. You are going to have to go back to the autoclave fixtures at the very least. Since growth is (at best) linear you cost of quartz will scale with the size of the blank. I’d bet it scales a bit more than that if you want to keep the material at a high level of performance.
> 
> You've explained the excuses vendors give for not making full
> size crystals.  But the question is, given these realities,
> does this reduce the theoretical advantage of the lower frequency
> and by how much?
> 
> Rick Karlquist N6RK
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