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

[Steve Rooke]

Warren,

Penny dropped!

On 14 June 2010 05:29, WarrenS <warrensjmail-one at yahoo.com> wrote:
> Magnus Posted
>
>> "The TPLL is a mid-tau stability test, since it's sweet-spot is in the
>> 0,1 - 1000 s range. Short-term is better handled in LPLL phase-noise
>> measurements."
>
> Mostly agree, it is a mid-tau device, but also consider:
>
> The simple TPLL can be used to find the 1ms to 10 ms ADEV as good and maybe?
> better than ANYthing else.
> AND I use it to find the drift and ADEV of my dual oven HP 10811's out to
> weeks, so there is no long term limit.
> (the trick is to control the DUT and not the Reference when doing long term
> testing)

Of course, provided that the DUT has an EFC, you can put this in place
of the "reference" oscillator and put a, say, GPSDO in place of where
the DUT normally goes. This will certainly extend things at long Tau
out as far as you wish. As for short tau, it would be better to
convert the circuit to LPLL.

> BUT
> I find the TPLL method is useful for MUCH more than just getting ADEV data.
> As such it's "sweet spot" extends from below 0.004 ms  (250 Hz)
> all the way up to >> weeks, when the DUT is the controlled Osc.

Either 0.004 s or 4 ms methinks. You would have to make sure that the
B/W from the mixer out right to the ability to control the reference
oscillator is that wide. This could be verified by breaking off the
EFC and injecting 250Hz into there and seeing if the original feed to
the EFC follows it.

> ALSO the simple TPLL is very Good and useful for seeing and measuring the
> effects of temperature, line noise, vibration, PS,  load, and just about
> everything else that effects the frequency stability of an oscillators below
> 1 KHz or so.

Providing that the reference oscillator is not subjected to those
effects at the same time (isolation).

> 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).

If you have some "stock" items that you can borrow for this job and
not just dedicate it to the TPLL. Still, that is not an unreasonable
assumption for many.

> If still in doubt about some of the TPLL's other high end performance
> capabilities, try the swinging osc test with ANYthing else and see if you
> can match the simple TPLL's performance.
>
> If one would make a list for the non ADEV uses and advantages of the simple
> TPLL
> It would indeed be very long list, and it does not take any fancy write up
> to see that, just a bit of open minded thinking.

But can it make a decent cup of char?

> 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,

Can you add a cup-holder, those are essential these days.

> just by changing a few jumpers and values.
> But those things are for later discussions, one windmill at a time.

So does it grind wheat to make flower then; by golly, this thing is versatile.

Add smilies as you see fit.

Cheers,
Steve

> ws
>
>
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-- 
Steve Rooke - ZL3TUV & G8KVD
The only reason for time is so that everything doesn't happen at once.
- Einstein