Short-term characterization of GPS disciplined oscillators and field trial for frequency of Italian calibration centres

Quartz and rubidium oscillators disciplined by the signals of the Global Positioning System satellites (GPSDOs) are increasingly used as traceable reference standards in calibration centres. These devices were characterised in the past at the Time and Frequency Laboratory of IEN concerning their long-term behaviour. Recently, evidence was found of short-term frequency instabilities, not previously detected, that must be taken into account in the frequency calibration field. The short-term instability results obtained at IEN on some GPSDOs are reported. An assessment of these features by a field-trial on frequency, was carried out among some Italian calibration centres equipped either with GPSDOs or other frequency references.