Off Air Atomic Clock MSF/GPS

MSF / GPS Receiver NTS-MSF-G/M-01

Now Verified and approved by the National Physical Laboratory.


Overview: Since the move of the MSF transmitter from  Rugby to Anthorn in Cumbria, many of the existing MSF receivers are failing due  to the extended range of reception necessary and a general increase in radio  noise around the MSF frequency of 60 KHz. To overcome this situation a more  intelligent radio receiver has been developed and seamlessly combined with the  absolute time reference from the GPS system.  This realises a very robust,  dual signal source, time code reference that provides uninterrupted time to  Universal Accuracy together with automatic BST/UTC (GMT) change over within the  time code.

Description: The Navtech  Systems MSF/GPS receiver is the latest ‘state of the art’ facility for  accessing the extremely accurate timing information broadcast by the UK MSF  transmitter and the US GPS satellite constellation. An integrated DSP-based MSF  receiver (able to process two antenna feeds simultaneously) with an (optional)  extremely sensitive 12-channel GPS receiver provides for the most comprehensive  off air timing reference available.

Timing, status and signal quality information  is displayed on an internal LCD panel. Regenerated MSF information, completely  locked to the received MSF signal, is output for connection to third party MSF  decoders via a 3.5mm mono jack plug. A multi-function RS-232 port allows for  connection to a PC.  Model versions are  differentiated by the presence or absence of a GPS receiver (G = GPS and MSF, M = MSF only).

The complete system comprises of either two  or three small weatherproof plastic housings. In the three-box version, two  contain the tuned ferrite antennas together with filtering and signal  amplification; these are connected to the third enclosure, containing the DSP  receiver (via coaxial cables with TNC fittings). A single 12V DC input is made  to the receiver housing; power for the antenna signal amplifiers is via their  coaxial interconnection cables.

MSF antennas: Signals from one or two ferrite rod antennas  may be processed simultaneously.  The  receiver module continuously monitors the signals available from the two  antennas. It also continuously monitors the signals available from its  integrated GPS receiver (if fitted).

MSF/GPS: The device automatically selects which of the  signal sources to use at any time by monitoring the measured signal quality  parameters. GPS is used in preference to MSF when five or more satellites are  visible.

The signal source being used at any time is  indicated on the unit’s LCD display. An ‘event log’ records the last 1000  signal source changes. This log is accessible via a PC connected to the unit’s  RS-232 connector if desired. When switching between sources or in the event of  poor signals from all external sources, the unit’s internal clock provides  continuous time output. This internal clock is phase locked to the MSF signals  and enables completely seamless source switching.

In the rare event both MSF and GPS become off  line the internal phase locked clock maintains an accurate time code for  several hours until either MSF or GPS time is restored.