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Requirements and Specifications for Installing a GNSS Antenna

 

This section describes the guidelines and procedure for installing a global navigation satellite system (GNSS) antenna to ensure an optimal signal reception. The ACX500 routers use the GNSS signals for timing and synchronization features.

Note

The GNSS port and LEDs on the ACX500 router chassis are labeled GPS.

Consider the following guidelines before you install the GNSS antenna:

  • RF site survey for antenna location

  • RF environment details, such as transmission source and proximity

  • Grounding plane

  • Cable routing

We recommend the guidelines and procedure described in this chapter to ensure optimum GNSS signal reception for the ACX500 router.

Requirements for Installing a GNSS Antenna

This section describes the requirements to correctly install a GNSS antenna on an ACX500 router. Table 1 lists the items that you must provide to install the GNSS antenna.

Table 1: Antenna Mounting Requirements

Item

GNSS L1/G1 antenna with a frequency band of 1575 to 1610 MHz +/-10 MHz, 3 dB bandwidth

Antenna mount that is used to secure the GNSS antenna

Mounting area clear for at least two meters of any metal or other material that could act as a shield and block the GNSS signal

360° unobstructed clear view of the sky from 15° above horizon

Clamps, cable ties, and so on, to secure cable

ACX500 Router GNSS Antenna Signal Gain Requirements

The ACX500 router requires an active GNSS antenna with built-in low-noise amplifier (LNA) for optimal performance. The LNA amplifies the received satellite signals first to compensate the loss due to the cable, and second to lift the signal amplitude to a range that is required by the receiver.

The cables and connectors that are used to connect the GNSS antenna to the receiver cause signal loss, which can be up to 13 dB. The signal gain due to the LNA amplification can be up to 30 dB.

When calculating the required signal for the router, keep in mind the loss due to the cables and connectors, and the gain due to the LNA amplification. Therefore, if the loss due to the cables and connectors is 13 dB and the LNA signal gain is 30 dB, then the signal gain available to the receiver is 17 dB. We recommend that you limit the available gain to less than 35 dB. Also, ensure that the LNA you select has a low noise profile.

The recommended range of the LNA signal gain, after compensating the loss due to the cables and connectors, at the receiver is 22 dB through 30 dB (with a minimum of 17 dB and a maximum of 35 dB).

General ACX500 GNSS Antenna Mounting and Installation Recommendations

Ideally, the GNSS antenna should be mounted where a 360° unobstructed clear view of the sky (at 15° angle from horizontal) is available to enable a connection to visible GNSS satellites. The ideal mounting location is a roof, tower, or an antenna mast, high above any obstruction or any device that can cause signal interference. We recommend a location that has the following characteristics:

  • Clear unobstructed view of the sky in all directions—360° view.

  • Away from high-power transmitters and radar antennas.

  • At least 3 feet (1 m) away from any metallic objects, such as radio tower, other antenna mast, electrical poles, and so on.

  • At least 3 feet (1 m) below the highest point of a lightning rod.

  • Convenient path for running the outdoor coaxial cable from the GNSS antenna to the network.

  • Install the router in compliance with the local, national, or international electrical codes:

    • United States—National Fire Protection Association (NFPA 70), United States National Electrical Code, Article 810

    • Canada—Canadian Electrical Code, Section 54

  • Protect the GNSS antenna from environmental conditions such as foot traffic, standing water, and any mechanical stressor that might compromise the cable integrity. Wherever applicable, run smaller size cabling through dedicated outdoor-rated electrical conduit.

Warning
  • Locate the GNSS antenna away from power lines, lighting systems, HVACs (heating, ventilation and air conditioning), and power circuits.

  • When installing the GNSS antenna, do not touch power lines or other sources of “live” power.

  • Have a qualified technician or a certified electrician perform the installation.

  • Observe all local and regulatory standards and ordinances.

  • Grounding the unit (metal mast or ground cable to the unit’s base) is required for the lightning protection to work properly.

The ACX500 Timing Server can maintain accurate time even if an antenna is mounted in a location that has limited visibility of GNSS satellites; however, we recommend obstructions should be minimized. Limitations to satellite visibility for an antenna include overhanging foliage or tall structures. Such structures can block the GNSS signal from the antenna and cause gaps in the GNSS satellite signal reception. In locations where satellite visibility is limited, keep in mind the following guidelines:

  • Position the antenna on the side of the structure with good visibility toward the equator where more satellites are visible. For example, if you are in the northern hemisphere, place the unit on the southern side of the structure unless that view is restricted or blocked. If that view is restricted or blocked, place the unit on the east or west side of the structure. Avoid the polar side where there are fewer visible satellites.

  • Ensure that the GMT time zone parameter is set while you configure the Timing Server.

  • To avoid any potential damage to the GNSS antenna and the router, do not install the antenna in the proximity of any transmitting RF or high-voltage power sources. This is both a hardware precaution as well as a personnel safety precaution. Follow all local building code requirements, as well as the local building electrical codes for power and grounding.

  • You must mount the antenna above and away from any electrical systems such as lift mechanisms, air handlers, HVACs, and other electrical or mechanical machinery.

  • The GNSS signals can be reflected by objects such as metal, walls, and shielded glass parts. Do not install the antenna near good light-reflecting surfaces. Failing to do so might result in distorted GNSS signals.

  • To avoid multipath reflections, do not place the antenna near a wall, window, or other large vertical objects.

  • To prevent damage from lightning, do not place the GNSS antenna at the highest point of the building.

  • You must locate the GNSS antenna at least 3 feet (1 m) away from any metallic objects such as radio tower, other antenna mast, electrical poles, and so on. See Figure 1.

  • Allow at least 6 feet (2 m) of separation between GNSS antennas. See Figure 1.

  • The antenna must have an unobstructed 360° view of the sky from 15° above the horizon. See Figure 2.

  • Locate the antenna within a reasonable distance of the building cable entry point.

  • Mount the antenna to any fixed surface by using the GNSS antenna mast or stanchion clamp. You may install the antenna to a vertical or horizontal surface based on the surface availability as long as the other antenna placement requirements are met.

  • You must connect the GNSS antenna to a surge or lightning arrestor. The surge arrester must be near the antenna location or at the building entrance, and must be grounded to the building ground. This ensures that the antenna has a direct path to ground and is away from any sensitive electrical or electronic GNSS equipment.

  • You must protect the GNSS antenna cabling from environmental conditions such as foot traffic, standing water, and any mechanical stress that might compromise or affect the cable integrity. We recommend, where applicable, to run smaller-size cabling through a dedicated outdoor-rated electrical conduit.

Figure 1: Antenna Clearance Requirement—Peripheral
Antenna Clearance Requirement—Peripheral
Figure 2: Antenna Clearance Requirement—Field of View
Antenna Clearance Requirement—Field
of View

Tools and Parts Required to Install the GNSS Antenna

Table 2 lists the parts of a standard GNSS antenna kit and other items required to install the GNSS antenna.

Table 2: Standard Antenna Parts, Tools, and Other Required Items

Item

GNSS L1/G1 antenna with a frequency band of 1575 to 1610 MHz +/-10 MHz, 3 dB bandwidth

Antenna mount that is used to secure the GNSS antenna

Antenna specific base adaptor

Antenna stanchion or mast

Antenna-specific cable connector

Cable continuity tester

Lightning arrestor and grounding strap

RF antenna installation kit

NO-OX anti-corrosion compound (for cable connections, grounding connector, and ground lugs)

Clamps, cable ties, and so on, to secure cable

Figure 3 shows the GNSS antenna parts in a typical installation.

Figure 3: Standard GNSS Antenna Parts
Standard GNSS Antenna Parts

Installing the ACX500 GNSS Antenna

To install the GNSS antenna, follow the guidelines specific to the selected GNSS antenna.

The following steps are part of a general procedure for installing any standard GNSS antenna:

  1. Mount the antenna to any fixed surface by using the GNSS antenna mast or stanchion clamp in an area with clear and open view of the sky.
  2. Route the coaxial cable from the newly installed antenna into the building following the manufacturer’s antenna safety guidelines.
  3. Route the coaxial cable from the building’s head-end to the server’s installation site, and connect it to the router’s GNSS port (RF input). See Front Panel of an ACX500 Indoor Router and Top View of the ACX500 Outdoor Router for the GNSS antenna port location on the ACX500 routers.
  4. Verify that the router is receiving good signal through the GNSS antenna by observing the GPA 1PPS LED on the ACX500 router.
Warning
  • Have a qualified technician and or certified electrician perform the installation.

  • Observe all local and regulatory standards and ordinances.

  • Grounding the unit (metal mast or ground cable to the unit’s base) is required for the lightning protection to work properly.

Warning

Do not install the GNSS antenna near overhead power lines or other electric light or power circuits, or where it can come into contact with such circuits. When you install the antenna, take extreme care not to come into contact with such circuits, because they might cause serious injury or death. For proper installation and grounding of the antenna, refer to local, national, and international electrical codes (for example, U.S.: NFPA 70, National Electrical Code, Article 810; Canada: Canadian Electrical Code, Section 54; and so on).



Warnung Installieren Sie die GNSS-Antenne nicht in der Nähe von Überlandleitungen oder anderen elektrischen Licht- oder Stromkreisen, wo sie mit solchen Schaltungen in Kontakt kommen können. Gehen Sie bei der Installation der Antenne mit äußerster Vorsicht vor, damit Sie mit diesen Schaltkreisen nicht in Kontakt kommen, da dies zu schweren Verletzungen oder zum Tod führen könnte. Informationen zur ordnungsgemäßen Installation und Erdung der Antenne entnehmen Sie den örtlichen, nationalen und internationalen elektrischen Richtlinien (zum Beispiel US: NFPA 70, National Electrical Code, Article 810; Kanada: Canadian Electrical Code, Abschnitt 54 usw.)

ACX500 GNSS Antenna Power Specification

Table 3 lists the electrical power specification for the ACX500 GNSS antenna.

Table 3: Electrical Power Specifications of ACX500 GNSS Output Connector for Antenna Power

Output Current (mAmp)

(I-Load)

Output Voltage (V)

45 mAmp (maximum)

Vout = 3.3 V (+/-5%) – 22 ohm x I-Load

Note

ACX500 GNSS output current supports only 3 V antenna voltage, which work with maximum current and supports voltage tolerance as calculated in Table 3.

For antennas that do not have a voltage rating of 3 V DC, we recommend that you use an active splitter or amplifier as required (DC block from ACX500 and antenna power from external power source) that supports the antenna voltage.

ACX500 GNSS Antenna Surge Protection

For a roof antenna, we recommend that you provide additional surge protection in accordance to the regulations and standards for lightning protection in the country where the ACX500 router is installed.

Note

We recommend that you use an external first-level fast lightning protector that has clamping voltages of 15 V and 20 V.

Warning

Make sure that grounding is available and that it meets local and national electrical codes. For additional lightning protection, use lightning rods, lightning arrestors, or surge suppressors.

Antenna Installation Verification

After installing the GNSS antenna, verify that the installation is properly done:

  • Verify that all the cables and connectors are installed correctly and securely fastened. Ensure that all connectors have been protected from weather by using the latest RF cabling installation and protection guidelines.
  • Verify that the GNSS antenna interface status is good in the respective GPS monitoring application. Also, verify the status of the GPS 1PPS LED on the ACX500 router.
  • Verify that the cable service loop or the drip loop is utilized and is sufficient.
  • Unlike other radio device, do not apply any tape or chemical protection to the connectors. The recommended connectors are weatherproof, and adding any protection makes the warranty void and can lead to expensive repairs.