[time-nuts] TICC vs 5370A

Orin Eman orin.eman at gmail.com
Fri Mar 31 02:23:57 EDT 2017

Back from the distraction of the LTE-Lite's PPS to see how the TAPR TICC
compared to my 5370A.  FWIW, the last time I did the simple operator
checks, the 5370A was well within spec, though I do have my doubts about
the long term stability of its OCXO.

In all these cases, I used the PPS from the Trimble Thunderbolt (with
sub-optimal antenna) as the input (Start input on the 5370A), terminated
with a Pomona 50 ohm BNC pass-thru adapter.  Will they be able to tell my
GPS antenna and location s*cks?

I used two 10MHz references, the 10MHz output from the 5370A (I know the
5370A 10MHz output can be improved, but it wasn't in this case) and an
FE-5680A clamped to a beefy heatsink, adjusted as well as I could to the
Thunderbolt 10MHz a few years back.

The Stop input on the 5370A and 10MHz on the TICC used the 10MHz reference
of choice.

In all cases, the 5370A Start input was set to positive edge, DC and the
trigger level at 0.5V.  The Stop input was also positive edge, but AC and
Preset trigger level.

The TICC is holding its own against my 5370A as far as I can tell - the
differences here are likely due to the poor GPS antenna location.  The main
advantage that I see for the 5370A is the ability to set the trigger level,
slope and so on - pick the right cable length and the reflections can cause
false triggering, though it was never a problem with the TICC.  When I get
chance I'll post a scope screenshot of one of the nastier falling edges
that caused false triggering - all bets are off if you trigger both on the
rising edge and falsely on a glitch on the falling edge of the PPS signal.

I've been suspicious about the OCXO in the 5370A and I suspect the poorer
performance when using it as a reference is due to random jumps in
frequency.  They are quite visible on the phase plot below (with linear
trend removed**).  I do wonder what that bump is at 45000 seconds on three
out of the four acquisitions is... they were not done at the same time.


**I forgot to undo the trend removal on one of the traces, so had to do it
for all of them.

[image: Inline image 1]

[image: Inline image 1]
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