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TimeProvider 2300/2700 User’s Guide
098-00564-000 Revision A3 – July, 2013
Appendix C Installing GNSS Antennas
Antenna Kits Overview
Antenna Kits Overview
When deciding on which of the available antenna kits meets your needs, the key
factor is the distance between the GNSS antenna and the TP 2700. There are
several coaxial cable lengths available to assist in receiving proper gains from the
GNSS antenna. Symmetricom offers five antenna kits for the TP 2700.
Considerations for Antenna Installation
When installing the GNSS receiver, it is important to select the proper gain antenna
and coaxial cable to account for the insertion loss between the antenna and the
GNSS receiver. Selecting the proper gain avoids under-driving or over-driving the
receiver antenna input. To acquire satellites, the gain required for a L1 signal at
1575 to 1606 MHz (with some level of signal attenuation allowed) for a GNSS
receiver input is defined in the receiver’s manufacturer’s specification.
L1 antenna gains are usually specified as the maximum effective gain. Such an
antenna can have 4.5 to 10 dB less signal strength at different satellite azimuths
and elevations, depending on their reception pattern. The GNSS engine requires a
net gain at the antenna connector input of the chassis to be between 15 to 30 dB.
All antenna kits include the GNSS L1 antenna, mounting pipe, floor flange, lightning
arrestor, pre-assembled coaxial cable (for antenna to lightning arrestor), roll of 3M
2150 weatherproof tape, and a SMA cable adapter. The antennas and in-line
amplifiers have TNC connectors and the lightning arrestor has N connectors.
All antenna kits supplied use a LMR-400, or equivalent, low-loss coaxial cable. The
L1 signal loss of LMR-400 is 0.167 dB/meter. The L1 signal loss of a 90 V lightning
arrestor is typically 0.25 dB. See
GNSS Antennas with Low Noise Amplifiers
The GNSS antenna kits provide reception of GPS and GLONASS satellite RF
signals in the range 1575 to 1606 MHz, each with the correct gain required to
provide timing stability for the coaxial cable length included in the kit. Additions or
changes to these kits may change the gain and prevent adequate satellite
reception.
For kit information, see
Accuracy of the antenna position determined using receiver survey depends on
providing RF gain to the GNSS receiver within a required range of 15 to 30 dB and
locating the antenna with an unobstructed field of view in a low multipath
environment. If these conditions are not met, the receiver survey will either require
longer than 20 minutes to complete or will not complete, preventing the GNSS input
from being used by the system as a reference. Also, timing stability will not be
optimized if these conditions are not met.
