RuggedCom RUGGEDSWITCH RSG2288 - Manual (Page 27)

3. Installation
RuggedCom® RuggedSwitch® 27 RSG2288 Installation Guide Rev 108
Color GPS Input IRIG-B PWM Input
no longer sees the minimum
number of required satellites.)
Off No signal detected No signal detected
Table 3.8. PTP Card LED Functions
3.3.2. GPS Antenna Installation
The signals received from the GPS satellite network are at a frequency of 1575.42 MHz with a
minimum power of -162 dBW. The GPS antenna must have a clear view of the sky in order to
receive the low power signals and track the maximum number of satellites. Rooftops or other
structures clear of obstructions and with a clear view of the horizon are ideal.
Elements of a typical GPS antenna system include the following:
• Active GPS Antenna (required)
• Coaxial cable to connect the elements (required)
• Lightning arrestor (optional)
• Line Amplifier or Filter (optional)
To ensure correct GPS signal reception, the overall system of antenna, cabling, lightning arrestor,
line amplifier and filters requires a relative gain which should be greater than 5 dBi but less than
18 dBi (to avoid signal saturation at the receiver input).
3.3.3. GPS Antenna Specifications
There are two major types of GPS antennas: passive and active. A passive antenna requires no
power and is an option when signal strength is not a concern. An active antenna has a built in Low
Noise Amplifier (LNA) to increase the strength of the signal, and to compensate for the signal loss
in a long cable connection. Active antennas are used when the antenna input is connected to the
receiver through a coaxial cable (usually longer than 3 m) or any high loss transmission path.
The PTP Card requires an active antenna with the following specifications:
Characteristic Active Antenna
Polarization Right-Hand Circular Polarized
Receive Frequency 1.57542 GHz ± 1.023 MHz
Power Supply 5 VDC
DC Current < 10 mA at 3 VDC
Antenna Gain Select antenna gain based on system configuration
Total Gain at PTP GPS Input (includes antenna gain, cable
loss, lightning arrestor loss, line amplifier gain and filter loss)
Total Gain ≤ 18 dBi
Axial Ratio < 3 dB
Output VSWR < 2.5
Table 3.9. GPS Antenna Specifications
• The PTP card’s GPS input provides 5 VDC at up to 10 mA to power the antenna.
• Best results can be achieved with a total gain of 16 dB (includes antenna gain, cable
loss, lightning arrestor loss, line amplifier gain and filter loss) at the antenna input.