Master Clock - How It Works
A small GPS receiving unit (GPS200A, NTP100, MCR1000, MCR5000 or GPSPCI) receives time information from the GPS satellites and generates time code and/or NTP (depending on the unit) that contains time and date information synchronized to the atomic clocks in those satellites. This signal can be read by any device that reads standard time codes such as the TCR1000 time code reader card, audio/video recording systems, time/date display clocks such as the NTDS26 and many other devices.
The TCR1000 reads the time code signal and synchronizes the PC clock. Software drivers provided with the card then synchronize time in computers and network operating systems.
| Masterclock Overview | NTP and Time Code Explained |
 Typical NTP Installation |
Typical Time Code Installation |
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The standard GPS200A antenna is approximately 3.5" (8.9cm) in diameter by 2" (5cm) tall, weighs 5.6 oz (160g) and has a threaded base for mounting on a 1" (2.54 cm) pipe - typically used for marine electronics antenna mounting. It is designed for Marine applications and is ruggedly built and water tight against normal atmospheric moisture, rain and ice. The standard antenna has a built-in preamplifier (32 dB gain) and requires 5 VDC which is supplied by the GPS200A receiver. The antenna connector type is SMA.
The process for determining if a given antenna location will work is not difficult but since each installation is somewhat different it can best be determined empirically. Depending on the type of building where the GPS200A is located and obstructions that may block reception of signals from the GPS satellites, the antenna may have to be located where it has an unobstructed view of the sky. In some cases this can be accomplished by placing the antenna adjacent to a window. In most cases it will require mounting outside of the building.
If possible the antenna should be mounted on the roof of a building. The antenna does not require height, only a clear unobstructed view of the sky. The antenna should be protected from lightning and falling ice/objects. Mounting close to a high power transmitting antenna could damage the preamplifier and/or prevent proper reception of the GPS signal.
The antenna is normally supplied with 50 ft (~15m) of low loss coaxial cable. If a longer cable is required, cables of various lengths (up to 500') are available from Masterclock®. The coaxial cable that is supplied by Masterclock® is a very low loss type at the operating frequency of the GPS system (1575.42MHz).
Generic RG-58 or RG-8 coax will not work and should not be substituted
unless you are familiar with the technical variables that are involved.
Because of the operating frequencies involved with the GPS signal, splicing or using adapters to extend the length of the antenna coaxial cable is not recommended and will likely prevent the system from operating properly. Use a single length of coax without splices or adapters.
Cables recommended by Masterclock® are Belden - #8219 (or equivalent) for lengths up to 75 ft (23m) and #9913 for lengths between 75 ft (23m) and 500 ft (152 m). Both cable types use standard SMA connectors. Plenum rated cables are available - contact factory for details.
In permanent installations, an outside antenna is recommended.
SMPTE and IRIG time codes are audio signal similar to that of a modem and can be routed over unshielded wire such as a telephone or, if desired, over an RG-58/59 coaxial cable. The GPS200A has a DB-9 male output connector - the TCR1000 has a DB-15 female input connector. These devices are provided with adapters to convert from the DB-9 and DB-15 connectors to BNC. The necessary connectors and wire can also be purchased at a Radio Shack or other electronics supply store or from Masterclock®.
