tinyPFA – Trimble Thunderbolt GPSDO vs Leo Bodnar Precision GPSDO

TinyPFA is firmware from Erik Kaashoek for NanoVNA-H4 hardware for accurate measurement of oscillator and clock source stability.

This article documents a comparison of:

  • a Trimble Thunderbolt GPSDO; and
  • a Leo Bodnar Precision GPS Reference Clock.

Above, the Trimble Thunderbolt was purchased used and packaged to reduce temperature and frequency variations.

Above, the Leo Bodnar GPSDO.

The Trimble is a quite old product now, but with a good reputation (though I had an earlier Trimble based GPSDO that did not handle the first GPS week rollover).

I thought it interesting to compare the two by way of Allan Deviation plots of each against a fairly good ovenised crystal oscillator (OCXO) in a Motorola R2009D service monitor, and then the two GPSDO with each other.

Above are the plots of Allan Deviation over 15m for the combinations.


My analysis of this simple experiment is that:

  • the long term stability of the OCXO is not as good as either GPSDO (no surprises there); and
  • the Trimble has lower jitter in the very short term than the  LeoBodnar GPSDO, but in the longer term, it probably has similar stability to the Trimble.