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" <jmi...@pop.net>
To: "Discussion of precise time and frequency measurement"
<time-nuts@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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