AiV Nixie clocks are equipped with a built-in GLONASS/GPS satellite navigation system signal receiver for the time and date synchronization. GLONASS/GPS satellites transmit the exact time by which the clock automatically synchronizes its time. In AiV Nixie clock a Fastrax IT530M, receiver based on MT3333 chipset is used. Receivers on this chipset have a low power consumption and a high sensitivity.
The main requirement to GLONASS/GPS receiver used in the clock is its sensitivity during the satellite search. Especially, during the first actuation, the so-called “cold start”. The clock is installed not outdoors but deep indoors, therefore the receiver’s capability to receive the weak satellite signal is critical. For this receiver the “cold” start sensitivity is 148 dBm. After the receiver has found the satellites, its switches over to the satellite tracking mode and its sensitivity increases to 165 dBm. So it is more difficult for the receiver to receive the satellite signals during the actuation than to track them later. If the receiver has determined the location by the satellites and supplies a valid solution, the error of the time supplied (unsynchronization with the UTC) does not exceed 1 microsecond.
But even the absolutely best receiver does not work without an antenna. As a rule, even more depends on the antenna than on the receiver. Due the fact that the satellite signal is very weak, a good antenna is necessary. An active antenna is extremely desirable. Tube clocks quite often make use of small-size solutions with a built-in antenna, like in Fastrax UC530M receiver. This antenna is capable of “seeing” satellites only outdoors. Even in the car the reception quality is poor. During AiV Nixie development the long-term experience of the design of GLONASS/GPS devices was used. Our experience shows that a sufficient reception quality is provided by antennas with the overall dimensions of minimum 20 х 20 mm. The optimum solution is the application of active ceramic antennas (with a built-in amplifier). For the application in poor satellite visibility conditions a dedicated reflection polygon behind the antenna is required. In AiV Nixie clock, alongside with Fastrax IT530M receiver, a 27 x 27 mm ceramic antenna with a 50 х 37 mm polygon for a stable satellite signal reception in complicated conditions is used.