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On 6/26/19 11:22, Paul Theodoropoulos wrote:<br>
<blockquote type="cite"
cite="mid:7b777e2c-2897-4647-567a-f0190a2df63f@anastrophe.com">
wow, fascinating - I set my c-ntpsec PPS min/maxpoll to 2. The RMS
time jitter rose a fairly significant amount, from hovering around
0.6<span style="color: rgb(0, 0, 0); font-family: "Exo
2"; font-size: medium; font-style: normal;
font-variant-ligatures: normal; font-variant-caps: normal;
font-weight: 400; letter-spacing: normal; orphans: 2;
text-align: right; text-indent: 0px; text-transform: none;
white-space: normal; widows: 2; word-spacing: 0px;
-webkit-text-stroke-width: 0px; text-decoration-style: initial;
text-decoration-color: initial; display: inline !important;
float: none;">µs</span> to now 1.0<span style="color: rgb(0, 0,
0); font-family: "Exo 2"; font-size: medium;
font-style: normal; font-variant-ligatures: normal;
font-variant-caps: normal; font-weight: 400; letter-spacing:
normal; orphans: 2; text-align: right; text-indent: 0px;
text-transform: none; white-space: normal; widows: 2;
word-spacing: 0px; -webkit-text-stroke-width: 0px;
text-decoration-style: initial; text-decoration-color: initial;
display: inline !important; float: none;">µs</span> -- while
the RMS frequency jitter plummeted from hovering around 4ppb down
to, well, barely discernably above 0ppb on the graph. <br>
<br>
eh, saying it just doesn't tell the story - <br>
<br>
Time jitter: <a class="moz-txt-link-freetext"
href="https://i.imgur.com/jNlaAAj.png" moz-do-not-send="true">https://i.imgur.com/jNlaAAj.png</a><br>
<br>
Frequency jitter: <a class="moz-txt-link-freetext"
href="https://i.imgur.com/wAF2nu9.png" moz-do-not-send="true">https://i.imgur.com/wAF2nu9.png</a><br>
<br>
</blockquote>
I think maybe I'm hitting a bug or I'm just not understanding
(usually the latter), as it doesn't seem possible:<br>
<br>
<a class="moz-txt-link-freetext" href="https://i.imgur.com/LorPR2F.png">https://i.imgur.com/LorPR2F.png</a><br>
<br>
jitter fluctuating between 400 parts per trillion and 800 ppt?? From
a Raspberry Pi running at 1.4Ghz?<br>
<br>
That said, I switched to min/maxpoll 1 for PPS, and saw a
corresponding change - so Time jitter appears to be inversely
correlated to Frequency jitter - less frequency jitter, more time
jitter, and vice-versa. This is all fascinating.<br>
<br>
<br>
<pre class="moz-signature" cols="72">--
Paul Theodoropoulos
<a class="moz-txt-link-abbreviated" href="http://www.anastrophe.com">www.anastrophe.com</a></pre>
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