Description
The Quartzlock E8000-TT GPS Frequency and Time Transfer Reference is a breakthrough in exceptionally low cost, traceable, 1-U rack mount, calibration-free, off-air frequency & time standards. These very low cost references maintain the high frequency & time accuracy required for demanding applications.
The E8000-TT uses a commercial GPS timing receiver. This performs a self survey when moved to a new location, and stores the averaged position. The stored position is used when the unit is reset, and remains valid provided the unit is not moved.
With a valid stored position, the GPS receiver switches into over determined clock mode, and uses all satellites in view to provide the best possible estimate of GPS time, output as the rising edge of a pulse every second (1PPS).
The 1PPS output from the GPS receiver is phase modulated with a saw tooth with a peak amplitude of about 12ns. This is due to the finite clock resolution used in the GPS receiver.
The E8000-TT uses a Kalman filter to a) correct the local clock, which is an OCXO, and b) to smooth the 1PPS and remove the saw tooth modulation. The eventual 1PPS output from the E8000-TT has short term phase jitter of less than 1ns RMS.
When using short or medium baseline time transfer, both receivers will largely share the same constellation, and will therefore see the same offset from UTC.
The 1PPS output from the E8000-TT receiver can be offset by up to ±500ms in 1ns steps.
