[time-nuts] A comparison of the TAPR-TICC and BG7TBL FA1

[Mark Sims]

I did a comparison of the performance of the TAPR-TICC/TADD2-Mini divider and the BG7TBL FA1 frequency analyzer performance.  The reference clock for both devices was a 5071A cesium.   The device being tested was a Nortel NTPX GPSDO 10 MHz output.  Attached are screen dumps of the two Lady Heather runs.

The noisy orange plot in the TICC run is the measured frequency offset from 10 MHz.   The noisy blue plot in the FA1 run is the measured frequency offset from 10 MHz.  (Note the scale factor differences)    Looking at the SPAN value (the difference between the max and min frequency measurements) shows that the FA1 noise level is around 4 times higher than the TICC.  The FA1 ADEV measurements are around 3 time higher.   The FA1 may be better than the TICC at lower (<50 second) tau,  but I have no way to verify that.  The FA1 screen dump includes a histogram of the frequency measurements.

One issue with the FA1 is that it seems to have an inherent frequency measurement bias of around -0.0002 Hz.  See the "avg#" value in the lower left corner of the plot.  I get nearly the same bias values when measuring 1, 5, and 10 MHz signals.   (I added a setting in Lady Heather to specify a measurment bias correction value).  It is interesting that the same -0.0002 Hz bias was present in the original BG7TBL GPSDO.

TAPR TICC pros:
high performance
lots of measurement and configuration options
open source design

TAPR TICC cons:
more expensive
requires external dividers to measure frequency (and a second power supply)
no case

FA1 pros:
inexpensive (around $100), decent bang for the buck
no frequency divider needed, 1 .. 80 MHz range
very simple operation (no configuration needed)
nice small unit with an extruded metal case. 

FA1 cons:
only measures frequency (no way to test 1PPS signals)
around 3X-4x less performance than the TAPR TICC.
closed source "black box"
inherent minor frequency measurement offset

Lately BG7TBL has released the FA2.   This appears to be similar to the FA1, but it has some VERY nice features including a basic 1 Hz .. 200 MHz range plus a 30:1 pre-scaler allowing measurements to 6 GHz.  It as an LCD display, an internal (adjustable) OCXO and external freq ref input, reference output, selectable 0.1/1/10 second timebase.  Costs around $120 (with power supply)    If the FA2 measurement performance matches the FA1, it would be greatly preferable over the FA1.   I have an FA2 on the way.



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