[time-nuts] Advantages of GNSS ???

[Bob kb8tq]

Hi

Well, if you ever get back into it:

You play games with varicap diodes to straighten out the curve. You may bias them, you might 
put them in parallel, you might put a coil or a cap across them. You can get the curve plenty flat 
enough for a control loop.

Hopping / discrete steps generally means you have to much drive on the crystal or some other 
circuit gotcha. The crystal its self and the tuning diode have no steps in them. They just aren’t 
complex enough devices to get into stepwise behavior. 

Drive power on an OCXO will pretty much always be below a milli-watt. A typical design will be in 
the range of 1/10 to 1/100 of that power level. 

Bob

> On Jul 9, 2019, at 5:36 PM, Glen English VK1XX <glenlist at pacificmedia.com.au> wrote:
> 
> and non monitonicity in the device is the death of a control loops.
> 
> My attempts at building good OCXOs using cheap AT crystals in the 90s was thwarted by.... non monotonic bending crystals !
> 
> And everytime they would wake up, the monitonicity would be in a different part of the control curve....
> 
> and they exhibited hysteresis, like defined steps , this seems to be the case with most crystals, the harder you looked, the more undesirable imperfections you found...
> 
> 
> 
> On 10/07/2019 5:57 AM, David G. McGaw wrote:
>> Leo -
>> 
>> I do believe you mean non-monotonic, rather than non-monotonous. Not
>> being monotonous is a good thing.  :-)
>> 
>> David N1HAC
>> 
>> On 7/9/19 1:20 PM, Leo Bodnar wrote:
>>> It's not very good, it is highly non-linear and even wor
> 
> 
> 
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