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<p>Hi everybody,<br>
</p>
<div class="moz-cite-prefix">On 2020-05-05 15:22, Doug Curtis via
users wrote:<br>
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cite="mid:CACSTJtQicwpy0os=DMkb_NTu0WnJs0ku50XS7F5J51tH1MhjeQ@mail.gmail.com">
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<div dir="ltr">On Tue, May 5, 2020 at 2:51 PM Paul Theodoropoulos
via users <<a href="mailto:users@ntpsec.org"
moz-do-not-send="true">users@ntpsec.org</a>> wrote:<br>
<div class="gmail_quote">Only tangentially related - since only
two of the three are using the <br>
<blockquote class="gmail_quote" style="margin:0px 0px 0px
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Adafruit gps hat - are you regularly (weekly, biweekly)
downloading the <br>
satellite ephemeris data from mediatek?<br>
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<div> </div>
<div>I'm not familiar with that so I'll have to do some
reading on it. <br>
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<p>It should be useless for a receiver that is always on. The idea
is to load the GNSSr with a database of what the birds are
currently broadcasting to speed up acquisition. All that data is
broadcast, and your GNSSr will fetch it in real time from the
birds. What it hears is the current data, unlike a download
database that does age. In short, useful for cold start, not
useful after.<br>
<br>
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<br>
The most peculiar characteristic is the 'long wave' rise of
positive <br>
offset spikes followed later by negative offset spikes
(specifically the <br>
'server offset SHM1' graph). The only thing that it vaguely
matches up <br>
with is the local GPS long wave due to visibility. But again
- spikes <br>
would certainly not be an expected symptom of visibility!<br>
<br>
Are you using a common power supply/source for all three
pi's - including <br>
the ntpviz device?<br>
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<div>The ntpviz server is a separate Centos 7 server in my
rack on a different circuit. Each pi has its own power
supply and they are on separate circuits. I believe the pi3
and pi4 are using Canakit power supplies. Because of this
testing, each antenna is on a different side of the house
(west, south, and east). This does start me wondering the
cleaniness of my power at the house though. Since the
spikes don't seem to happen on all of them at the same 34
minute interval, I'm guessing it's probably not something
noisy on my house power. I did just receive a pi3 with an
office raspberry pi power supply and once I solder the
Adafruit breakout gps kit, I plan on testing with it as
well.</div>
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<p>How about power interference due to motors/heating/cooling? Your
graphs are very different from my spikes, btw<br>
<br>
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Pure shots in the dark. I've dealt with intermittent spiking
in the long <br>
ago past, with a resolution that is very unlikely to be
related (turning <br>
off the Monit monitoring application, which isn't part of
the default <br>
install of debian/raspbian)<br>
<br>
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<div>Thanks for the ideas. I've just removed the avahi daemon
and will check on the results of that. I plan to go through
and eliminate unneeded services one by one to try and narrow
this down further.</div>
<div> </div>
<div>Doug</div>
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Martin<br>
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