[time-nuts] Re: Best frequency to start for GHz synth ?

[Bruce Griffiths]

Poseidon Scientific Instruments (acquired by Raytheon) make a room temperature 10.24GHz Sapphire loaded cavity oscillator with a low PN floor:
https://www.rdi.uwa.edu.au/__data/assets/pdf_file/0012/3447669/Raytheon-TechnologyToday-20141-Extract.pdf

Bruce 
> On 02 April 2021 at 05:06 Chris Caudle <6807.chris at pop.powweb.com> wrote:
> 
> 
> On 2021-03-31 14:27, Richard (Rick) Karlquist wrote:
> > When I left Keysight in 2014, they were still trying to solve the
> > microphonic problem in their sapphire resonator oscillator.  Also,
> > it is still necessary to lock the oscillator to a 5 or 10 MHz
> > OCXO.  The oscillator is tuned by varying its oven temperature
> > set ppoint.
> 
> What kind of oven temperature range?  I thought sapphire oscillator was 
> pretty much synonymous with "cryogenic sapphire oscillator."  I found a 
> paper which described sapphire as a "low loss material with loss tangent 
> of 5×10^−6 at room temperature, 2×10^−8 at 77 K and 7×10^−10 at 4 K 
> giving Q-values of more than >10^7 at low temperatures."
> 
> That paper seemed to be describing some kind of temperature compensation 
> they  had developed to reduce the temperature sensitivity of 10ppm/K and 
> also move the turnover point from 77K to 92K.  92K isn't exactly what I 
> think of when I hear "oven" so presumably there is some mode that works 
> at around 300K that I didn't find discussed yet.
> 
> -- 
> Chris Caudle
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