[time-nuts] Advantages & Disadvantages of the TPLL Method

Steve Rooke sar10538 at gmail.com
Mon Jun 14 10:10:40 UTC 2010

Thanks Magnus!

On 14 June 2010 20:45, Magnus Danielson <magnus at rubidium.dyndns.org> wrote:
> Steve,
> On 06/14/2010 04:49 AM, Steve Rooke wrote:
>> On 14 June 2010 10:46, Magnus Danielson<magnus at rubidium.dyndns.org>
>>  wrote:
>>> Still puts it in the mid-tau range as a method. The useful range and
>>> precision of a particular implementation of the method will vary.
>> By putting a GPSDO in the usual place of the DUT and putting the 10811
>> in place of the reference oscillator it could work well beyond the
>> 1000s point. CAVEAT: this only works for a DUT that has an EFC that is
>> reasonably linear.
> EFC linearity will remain an issue for analog oscillators. The oscillator
> gain will differ depending on offset voltage and temperature.
>>>> So if you are just thinking about the TPLL for taking ADEV data from 0.1
>>>> to 1000 sec, then you're are missing 90% of the other useful stuff it
>>>> can do as good or better than most anything thing else out there, and
>>>> all for the same $10 (my cost).
>>> The typical price-tag of a 10811 is in 100-150 USD. I think it is
>>> reasonable
>>> to assume that a TPLL weighs in at about 200 USD with all support mixers,
>>> amplifiers, ADCs etc. It's not bad, but if you don't have the parts
>>> that's
>>> about what you need to spend at least.
>> If you really wanted to be a scrooge, you could open the case on one
>> of those plethera of HP intruments and temporarily borrow that 10811
>> that is just sitting there. As for something like a ADC, you could
>> find a DAQ on fleeBay which could do duty here and also be a useful
>> tool for general purpose use. Heck, you can use your sound card to
>> digitize the EFC, provided it is DC coupled.
> If you don't have the parts, then it will set you back with at least that
> number. If you have the parts, you have already invested in them and payed
> for them that way. You may be lucky to be given the oscillator, but honestly
> you can't rely on that. I just want the cost numbers to be more reasonably
> given. It is still a fairly cheap solution.
>>>> BTW, with a couple of minor configuration changes, the TPLL BreadBoard
>>>> can be transformed into a LPLL,
>>>> so the usefulness of the basic Universal TPLL BB circuit has even more
>>>> possibilities.
>>>> In fact one could make yet another list of all the additional things it
>>>> can do with no added cost,
>>>> just by changing a few jumpers and values.
>>>> But those things are for later discussions, one windmill at a time.
>>> Measurement of phase noise is what the LPLL is good at, especially when
>>> done
>>> in cross-correlation mode. Interferometric setups use the mixers better.
>>> Both these techniques could be used for LPLL and TPLL measures.
>> Do you have some pointers to these setups please Magnus?
> Look at Enrico Rubiolas site where his publications and presentations should
> be inspirational. His focus is on LPLLs. but the methodology of
> cross-correlation and interferometric setup should be as viable in the TPLL
> world.
> Cheers,
> Magnus
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Steve Rooke - ZL3TUV & G8KVD
The only reason for time is so that everything doesn't happen at once.
- Einstein

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