GPS / GNSS NTP Time Server

A GPS / GNSS NTP time server is a network appliance that receives UTC time from navigation satellites and distributes it to computers, controllers and IEDs using the Network Time Protocol. Because its reference comes directly from satellite atomic clocks, it operates at Stratum 1, the most accurate level a local network can have. The PreciseSync SMC-300 series also provides IRIG-B outputs, so devices without network timing can follow the same clock.

All three share a multi-constellation GNSS receiver and OCXO holdover, and differ in form factor and resilience. The SMC-300 is a compact 1U rack server with the widest range of outputs. The SMC-300-R duplicates the GPS receiver, master clock, comparator unit and power supply in a 3U rack chassis for sites that cannot afford a timing outage. The SMC-300-D mounts on a DIN rail inside a control panel and provides IRIG-B (AM) and NTP over Ethernet.

The server keeps generating valid time from its internal oven controlled crystal oscillator (OCXO), rated at 10 PPB stability, until satellite lock returns. For sites expecting longer outages, a rubidium oscillator option offers 0.1 PPB stability with 1 µs holdover accuracy over 24 hours. A Form-C alarm relay lets your control system flag any change in receiver status.

The receiver tracks GPS (L1 C/A, L2C), GLONASS (L1OF, L2OF), Galileo (E1B/C), BeiDou (B1I, B2I) and NavIC-IRNSS across the L1, L2 and L5 bands. It uses a 184-channel parallel-tracking receiver with -148 dBm acquisition and -167 dBm tracking sensitivity. Tracking several constellations keeps the server locked at sites with a partly obstructed sky view.

The PreciseSync-SMC-300 achieves 14 ns timing accuracy with GNSS signal lock. On the SMC-300 and SMC-300-R, clock accuracy to UTC is better than 100 ns on 1PPS, TTL, fibre and AM IRIG-B outputs, and the NTP timestamp at the server is within 1 µs. Accuracy at each NTP client depends on your network architecture.

Yes. IRIG-B is available on all three models, which suits protection relays and IEDs with dedicated time synchronisation ports. The SMC-300 and SMC-300-R add 1PPS, DCF77, programmable pulses (PPS, PPM, PPH, PPD), serial and differential pulse outputs, so they can drive any number of slave clocks and digital displays. Output ports are customised to each order.

The SMC-300 and SMC-300-R are configured through a secure HTTPS browser interface using the Sertel Time Management Suite, or locally through the front-panel keypad. They support SNMP V1, V2C and V3 with trap generation, Syslog (RFC 3164 and RFC 5424), user-defined access control lists, and both IPv4 and IPv6. The SMC-300-D is set up through Sertel configuration software and shows Power ON and GPS Lock status on its front panel.

The series is tested for environmental and electromagnetic performance, including dry heat, cold and damp heat (IEC 60068-2-2, 2-1 and 2-3), sinusoidal vibration (IEC 60068-2-6) and dielectric strength (IEC 60255-5). Immunity testing covers ESD, radiated and conducted RF, fast transients, surges, magnetic fields, damped oscillatory waves and voltage dips under the IEC 61000-4 series, with emissions checked to IEC 61000-3-3 and CISPR 14-1.