[time-nuts] Re: 10 MHz TCXO periodically jumping 20 mHz up and down

[Magnus Danielson]

Hi Erik,

I only saw that thread later, and I will have to return to that as I 
have a little more energy.

I'm trying to get you up to speed with the many variants there is, and 
there is plenty experience here to feed from. What may be true for one 
device will not make any sense for another. Please feel free to ask 
questions on and off list. I've had to measure behaviours of many 
devices over the years. Eventually the reduced the range of devices I 
had to measure for qualification, since they learned what probably would 
not work.

For the price-range, manufactures have been very inventive in their 
approach to make compensations and also make a wide range of 
frequencies. Today we have frequency synthesis so the distributor can 
program the frequencies the customer wants. Now, combine that with TCXO 
and you can let that synthesis also synthesize the output frequency for 
compensation. Trouble is, it can cause jitter we do not want, but for 
many applications that's just fine, as they even want more of it for 
spread spectrum to make EMC compliance easier.

It might be that you are looking in the wrong range of oscillators for 
your type of application.

Also, beware that different vendors have their different tweaks. They 
may not even be the same over time. From bitter experience, check your 
second sources before putting them onto the second source list.

Spending a bit more can get you out of certain troubles.

I do not recall what your application of choice was, sorry if I missed 
that in the process.

Cheers,
Magnus

On 2022-02-18 12:52, Erik Kaashoek wrote:
> Hi Magnus,
> Tom also replied to my question and suggested a 107.34 seconds 
> interval related to dithering with a 1e7/2^30 interval
> Unfortunately the datasheet is rather short (sub $1 device) and does 
> not provide any hints to being a digital implementation.
> Thanks to all for helping!
> Erik.
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