[time-nuts] Sending me Lady Heather screen-captures....

WarrenS warrensjmail-one at yahoo.com
Tue Dec 29 19:31:36 UTC 2009


Mike

Assuming you have learned to tame some of LH behavior issues, and that is 
not what is causing the problems then:

> MB) the temperature graph exhibits a sharp, which recovers over a period 
> of a few minutes.
ws)    Likley a basic 'bug' in the LH Hardware. Best to ignore it.


> MB) blue PPS ADEV and the red OSC ADEV
ws)    The best thing I have found so far for most to do with the Blue and 
Red ADEV curves is to turn them off  using "GA"
They can provide some useful advanced information BUT they are not too 
comparable to 'standard' ADEV.


> MB) Periodically, the violet PPS graph and the green DAC graph will go off 
> scale for 10-15 minutes.
ws)    The really LARGE jumps can and most likely are caused when the Tbolt 
goes into and returns from holdover.
To verify if that is your cause, Look at the "Sat Counts" LH plot, if it 
goes to zero, then that is what is happing.
Also check the 'holdover sec", That counts how many seconds has been spent 
in holdover.
IF Holdover is the cause then setting  the AMU down to around 1.0 from the 
default 4.0 can help
IF you can not get a better signal and view from your antenna.

If you set the Elevation up to around 25 to 30 and set the TC to 250 + from 
the default 100
both of these will help reduce the smaller jumps, even when your antenna has 
a good signal.

And to reduce the Phase error that the Higher TC will cause with changing 
temperature and ageing
reduce the Damping setting from the 1.2 default to 0.7. And before doing 
that set the 'Dac gain' correct.

It's all a compromise, but with some effort and experience you can make 
things much better over the default settings.

If you send me a LH screen dump or better yet a 24 hr log plot, I'd better 
be able to point out the causes of you problems without all the guessing.

have fun
ws

****************
From: "Mark Sims"

Those spikes/decays in the temperature plot are due to false readings the 
Tbolt firmware gets from the temperature sensor chip.  They are an artifact 
of how the temperature sensor works in its "high resolution" mode.  They are 
actually single sample spikes of 1C (I think) in the output of the sensor 
chip.  The reported amplitude/decay is due to the filtering the Tbolt 
firmware does on the temperature readings.

Also,  remember that the ADEV values calculated by Lady Heather are from its 
internal measurements of the oscillator and PPS signal against the 
rather-noisy-in-the-short-term GPS signal.   They tend to depart from the 
true ADEV values measured against a real external reference particularly at 
shorter values of tau (like <100 secs).

Turn on  the satellite count display (G C from the keyboard in ver 3.0). 
The Tbolt reacts rather poorly to changes in the group of satellites that it 
is tracking.   When the tracked satellite constellation changes,  you can 
get big jumps in the osc/pps/dac signals.

To minimize constellation changes,  set the signal level mask to a low value 
(like AMU=1.0) and the satellite elevation mask to a high value (like 25 
degrees).

----- Original Message ----- 
From: "John Miles" <jmiles at pop.net>
To: "Discussion of precise time and frequency measurement" 
<time-nuts at febo.com>
Sent: Monday, December 28, 2009 10:26 PM
Subject: Re: [time-nuts] Sending me Lady Heather screen-captures....


>
>> One mystery is that once or twice daily, the
>> temperature graph exhibits a sharp, almost perfectly
>> vertical spike which recovers over a period of a
>> few minutes.  The temperature cannot possibly change
>> that rapidly so there is something else going on.
>>
>
> Note that the existing (non-beta) version of LH has some pretty debatable
> serial-port code in it.  You may just be seeing data corruption.  If it
> happens with the 3.0 beta version, it's may be worth investigating.
>
>> LH often indicates that the blue PPS ADEV and the
>> red OSC ADEV are both in the high E-13 zone for several
>> hours and then invariably, both will drop back to the
>> mid E-12 zone and sometimes stay there for many hours.
>
> Nature of the beast, really.  A single outlier can affect your whole ADEV
> plot.
>
>> Periodically, the violet PPS graph and the green DAC graph
>> will go off scale for 10-15 minutes and I cannot find
>> a reason for this-- it does not seem to be either
>> temperature related or have anything to do with how
>> strong the signals from the birds are or where the birds
>> are relative to any tall tree foliage blocking the antenna
>> sky view.
>
> The auto-scaling has undergone some improvements, too... if you're not
> running the beta, give that a try.
>
> -- john, KE5FX
>

***************
From: "Michael Baker"
> Hello, Time-Nuts--
>
> Many thanks to Warren S for sending me over 20
> Lady Heather screen-captures showing different
> configurations!!  I really appreciate seeing these
> and welcome anyone else on the list sending me
> their screen captures.  John Miles commented that
> individual screenshots may not be very useful without
> specifying the timescale, filters, and graphs you're
> looking for. This is true, but I am not even sure
> what I am looking for,--and some of the filter
> configurations mean nothing to me!!  At this stage,
> I am like the little boy on the sidewalk looking
> into the toy store window and saying, "WOW!! How COOL!!  Look at that, and 
> that, and that!!"
>
> Now I have some studying to do of the graphs of all
> the different filters and configurations-- this will
> take me a while as I am not really sure what I am looking
> at with some of the graphs.  Thanks again Warren!!
>
> My Thunderbolt sits next to my desktop computer
> in the shop and I have made no attempt to thermally
> isolate it from ambient temperature excursions
> due to routine air-conditioner cycles in the
> summer and heat-pump cycles in the winter so I expect
> to see some regular variation of the temperature
> graph.  I mainly use it's outputs to reference and
> lock my spectrum analyzer and frequency counters with.
>
> One mystery is that once or twice daily, the
> temperature graph exhibits a sharp, almost perfectly
> vertical spike which recovers over a period of a
> few minutes.  The temperature cannot possibly change
> that rapidly so there is something else going on.
>
> LH often indicates that the blue PPS ADEV and the
> red OSC ADEV are both in the high E-13 zone for several
> hours and then invariably, both will drop back to the
> mid E-12 zone and sometimes stay there for many hours.
>
> Periodically, the violet PPS graph and the green DAC graph
> will go off scale for 10-15 minutes and I cannot find
> a reason for this-- it does not seem to be either
> temperature related or have anything to do with how
> strong the signals from the birds are or where the birds
> are relative to any tall tree foliage blocking the antenna
> sky view.
> Mike Baker
> -----------------------------------------------
>
>




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