NTP100-GNSS vs NTP100-OSC vs NTP100-TC: which one do I choose?
NTP100-GNSS, NTP100-OSC and NTP100-TC are the three flavours of Masterclock's compact LAN time server, each using a different reference source: GNSS satellites (GNSS), internal high-stability oscillator (OSC) or existing IRIG or SMPTE time code signals (TC). Below you can read which variant suits your situation, based on the current datasheets.
Quick recommendation
- Choose the NTP100-GNSS when you can place an antenna on the roof. The supplied weather-proof antenna (5 m coax) or the optional kit (15 m) gives you Stratum 1 accuracy via GPS, with holdover upgrade to OCXO as backup.
- Choose the NTP100-OSC for indoor or Faraday environments without antenna view, and when you can rely on an external NTP pool or an upstream GMR grandmaster as a regular reference. Fully autonomous deployment.
- Choose the NTP100-TC when an IRIG-B or SMPTE time code signal is already present, for example from an existing broadcast infrastructure or GMR grandmaster with time code output, and you want to translate that signal to NTP for your IT network.
Specifications side by side
| Feature | NTP100-GNSS | NTP100-OSC | NTP100-TC |
|---|---|---|---|
| Time reference | GPS satellites (Stratum 1) | Internal TCXO or optional OCXO (autonomous) | Existing IRIG or SMPTE time code signal |
| NTP output accuracy | ± 2 ms | ± 2 ms | ± 2 ms |
| Antenna required | Yes (supplied, 5 m coax, optional 15 m kit) | No | No |
| Time code input | Not standard | Not standard | IRIG-B0 (DCLS or PWM), IRIG-B1 (AM), SMPTE 12M (30/25/24 fps non-drop) |
| Display | 6-digit LED (red) | 6-digit LED (red) | 6-digit LED (red) |
| Standard oscillator | TCXO ± 3 sec/year | TCXO ± 3 sec/year | (no internal disciplining, TC-driven) |
| Holdover option | OCXO: 1 ppb/day (± 250 ms/year) | OCXO available as standard, 1 ppb/day (± 250 ms/year) | OCXO: 1 ppb/day (± 250 ms/year) |
| Holdover at power loss | Battery-backed RTC ± 1 min/year | Battery-backed RTC ± 1 min/year | Battery-backed RTC ± 1 min/year |
| Network | RJ45 10/100 Mb, IPv4/IPv6, DHCPv4/v6, SNMP, SSH or Telnet | RJ45 10/100 Mb, IPv4/IPv6, DHCPv4/v6, SNMP, SSH or Telnet | RJ45 10/100 Mb, IPv4/IPv6, DHCPv4/v6, SNMP, SSH or Telnet |
| Additional connectors | RS-232 (DB9), USB, SMA antenna | RS-232 (DB9), USB | 3-pin terminal block (diff. TC), BNC (single-ended TC), USB |
| Napájení | 9-28 VDC (12 VDC adapter supplied), < 7.5 W | 9-28 VDC (12 VDC adapter supplied), < 7.5 W | 9-28 VDC (12 VDC adapter supplied), < 7.5 W |
| Form factor / weight | 16.4 × 10.3 × 3.7 cm, 454 g | 16.4 × 10.3 × 3.7 cm, 454 g | 16.4 × 10.3 × 3.7 cm, 454 g |
| 1PPS output (option) | Yes | Yes | Yes |
| Warranty | 5-year limited parts & labor | 5-year limited parts & labor | 5-year limited parts & labor |
When to choose each model?
NTP100-GNSS, Stratum 1 via GPS
The most popular NTP100 model. A weather-proof, pre-amplified antenna is supplied as standard with 5 m of coax. For longer distances (typically a server room beneath a roof) a 15 m kit is available. Once the antenna has lock, the NTP100-GNSS delivers Stratum 1 NTP with ± 2 ms output accuracy. Optionally GLONASS tracking can be enabled and the OCXO upgrade ordered for holdover during GPS outage (for example jamming, antenna cable damage or solar activity).
Typical scenarios where the NTP100-GNSS is the default pick: an SME or social-profit organisation with a single server room and roof view, an educational institution looking to provide NTP for a campus, or a production environment where one time server suffices for the production line and the office network. For networks with very many clients or for multi-site you move on to a GMR grandmaster.
NTP100-OSC, autonomous thanks to internal oscillator
The NTP100-OSC is identical to the GNSS variant in terms of network interface, but without a GNSS receiver. It relies on the internal TCXO (± 3 sec/year) or the optional OCXO (± 250 ms/year) and is often deployed as a secondary NTP source, fed by an external NTP pool or by an upstream GMR grandmaster. For sites without antenna view this is the appropriate variant: basements, Faraday environments, military cabinets or locations where roof work is not an option.
For mission-critical installations the NTP100-OSC with OCXO upgrade is deployed as an autonomous time server for networks that cannot permit external dependency. The recent NATO-NSPA delivery (Capellen, Luxembourg) used this configuration for multiple NSPA locations, a textbook example where GNSS antennas are not practical and autonomy via an internal oscillator is essential.
NTP100-TC, bridge from time code to NTP
The NTP100-TC has no internal oscillator disciplining and no GNSS receiver, but it does have time code inputs: differential via a 3-pin terminal block, or single-ended via BNC. It accepts IRIG-B0 (DCLS or PWM), IRIG-B1 (AM) per IEEE 1344 and SMPTE 12M (30/25/24 fps non-drop). This makes it the appropriate bridge between an existing time code infrastructure and your IT network: the incoming IRIG or SMPTE signal is converted to NTP for your clients.
Typically used in broadcast facilities where an SMPTE-LTC signal is already present, in observatories and test labs with their own IRIG-B source, or in installations where a GMR grandmaster is central and the NTP100-TC serves as a satellite time server per building or per VLAN segment to serve NTP clients. The OCXO option is especiálníly relevant here for holdover when the time code signal drops out.
Často kladené otázky
Can I deploy an NTP100 without an antenna on the roof?
Yes. The NTP100-OSC has no GNSS receiver and runs completely autonomously on an internal TCXO or OCXO oscillator. The NTP100-TC also operates without an antenna, but requires an existing IRIG or SMPTE time code signal as reference. Only the NTP100-GNSS needs a GNSS antenna (supplied: weather-proof antenna with 5 m coax, optionally 15 m).
Jaký je Stratum 1 status per model?
Stratum 1 means that the time server synchronises with an external reference (GNSS satellite, atomic clock or time code source). The NTP100-GNSS reaches Stratum 1 as soon as the GNSS antenna has lock. The NTP100-TC reaches Stratum 1 as long as the IRIG or SMPTE signal is present. The NTP100-OSC is not a Stratum 1 server without an external NTP pool: as standard it runs autonomously on its oscillator (Stratum 2-3 depending on topology) and is often deployed as a backup alongside a GNSS source.
What holdover performance is available on power or signal loss?
On loss of power, every NTP100 model falls back on an internal battery-backed real-time clock chip with ± 1 min/year (approximately 165 ms per day). With the optional OCXO upgrade the holdover stability is around 1 ppb per day (± 250 ms/year) after 30 days of aging, this is the typical choice for NTP100-GNSS installations that need to bridge several days of GNSS outage.
Does the NTP100-OSC fit in a network with an external NTP pool?
Yes. The NTP100-OSC is often chosen as a secondary stratum source in networks where a reliable external NTP pool is available. It can serve NTP clients itself and periodically adjust against the external pool. For sites without antenna view and without time code infrastructure, this is the appropriate variant.
Kolik clients can an NTP100 serve?
The NTP100 series is suitable for networks up to approximately 10,000 NTP requests per second, in practice that is enough for several thousand clients in a typical business environment. Above that limit, or when you need PTP, you move on to the GMR5000 or GMR6000 grandmaster.
Hesitating between GNSS, OSC or TC? Daylight bv has been advising on NTP installations across Europe since 2014. We help you with topology, antenna feasibility and holdover choices.
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