Symmetricom SyncServer S300

The Symmetricom SyncServer S300 is a dedicated stratum-1 NTP time server that can obtain accurate time from GPS satellites, AM radio signals (DCF, WWVB, JJY), or other NTP servers.

Mine has the optional rubidium oscillator, which keeps the time drift under 6 microseconds per day if the GPS time reference is lost.

The GPS input takes advantage of the fact that the antenna is stationary, so it can focus only on the time part of the GPS signal and average it over many satellites for added accuracy. The S300 requires a 12V GPS antenna.

I use a PCTEL GPS-TMG-HR-40NCM antenna (with built-in 40dB amplifier), mounted on my balcony (facing south), and it works quite well — usually there are about 4-6 satellites visible, which is enough to extract an accurate time signal.

If the GPS antenna is mounted outside (as it should be for best reception), it needs a surge protector in case of any nearby lightning discharges. I use a PolyPhaser IS-MR50LNZ+15, which passes up to 15V DC (needed to power the GPS antenna).

I have modified the S300 to add additional BNC ports for the 10MHz output signal, which I then use as a reference for my test equipment. The unit has no fans, so I added a small USB-powered fan to blow over the power supply section, as it got very hot without it.

If you want to carry out the modification too: compatible BNC ports are Amphenol RF 031-6577, then you only need to connect to the serial console and enter root eng sys cat "/dev/null && bash" to enter the shell, from where you can run /sbin/seeprom (select options 40 and 42), where you can enable the 10MHz output and other things.

These are pretty neat little devices, but the software on them is old, so don't expose them to the internet.

Pictures ^

S300 (front view)
S300 (back view)
S300 (inside view)
Rubidium oscillator
GPS board
Modem/LFR board
Power supply
Front panel board
Relay card
Voltage test pins
Mainboard (top view)
Mainboard (bottom view)
Mainboard (bottom view, close-up of the GPS antenna section)
CompactFlash cards
Mainboard with added BNC ports (top view)
Mainboard with added BNC ports (bottom view)
Mainboard with added BNC ports (bottom view, close-up of the GPS antenna section)
S300 (back view, with additional BNC ports)
S300 time display (variant 1)
S300 time display (variant 2)
S300 time display (variant 3)
PolyPhaser IS-MR50LNZ+15
PolyPhaser IS-MR50LNZ+15 (inside view)

Documents ^

Links ^


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