[time-nuts] LPRO testing

[John Miles]

If you have a TimePod or 3120A you may be able to capture an LPro warmup
cycle by selecting 500 Hz measurement bandwidth.  You will still get drift
warnings during the lock-search process but the data will probably be OK as
long as the swing isn't too radical.  

 

In this case, the LPro swept about +/- 150 Hz around 10 MHz before locking
up at about 120 seconds:

 



 

Zooming into the frequency-difference plot reveals that it continued to
settle down for the next few minutes:

 



You could get the same data from a counter, of course, just not at 1000
sample points per second. :)

 

(20+ MB  .TIM file at http://www.miles.io/lpro_coldstart.zip for those
interested)

 

-- john

Miles Design LLC

 

 

 

> -----Original Message-----

> From: time-nuts-bounces at febo.com [mailto:time-nuts-

> bounces at febo.com] On Behalf Of Bob Camp

> Sent: Sunday, January 20, 2013 12:18 PM

> To: Discussion of precise time and frequency measurement

> Subject: Re: [time-nuts] LPRO testing

> 

> Hi

> 

> Yes, unless you have some very unusual gear, it's tough to get a good view

> of the warmup / lockup sweeps *and* the performance of the LPRO after it's

> locked.

> 

> The main questions on the lockup sweep is going to be:

> 

> 1) does it make it to / past the right frequency?

> 2) how soon after it does get there, does it lock up?

> 3) if it doesn't lock up, does it do something odd as it sweeps past the
right

> frequency?

> 

> Not terribly complex.

> 

> Bob

> 

> On Jan 20, 2013, at 9:33 AM, Magnus Danielson

> < <mailto:magnus at rubidium.dyndns.org> magnus at rubidium.dyndns.org> wrote:

> 

> > On 01/20/2013 04:08 AM, Bob Camp wrote:

> >> Hi

> >>

> >> I just watch them with a reasonable counter that will give me 0.1 ppm

> resolution.

> >> Since the sweep is fairly fast, you can't have an overly long gate
time. The

> real

> >> thing you want to catch is the frequency at each end of the sweep. It
waits

> there

> >> long enough that you don't have to go crazy to catch it.

> >

> > As I suspected.

> >

> > I would have to switch mode for fine-tuning anyway.

> >

> > Cheers,

> > Magnus

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