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

Steve Rooke sar10538 at gmail.com
Sun Jun 13 22:49:41 EDT 2010


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.

>> 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.

>> 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?

Cheers,
Steve

> 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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