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An outside antenna system should not be located in the vicinity of
WARNING:
overhead power lines or other electric light or power circuits, or where it can fall into
such power lines or circuits. When installing an outside antenna system, extreme care
should be taken to keep from touching such power lines or circuits as contact with them
might be fatal.
C. Once a suitable antenna location has been identified, it is necessary to ensure that the
GPS signal that reaches the ATS-6501 is of suitable quality.
minimum of 15dB gain from the antenna gain combined with the amount of loss in the
antenna cable. The antenna included with the ATS-6501 has 25dB of gain so the total
cable losses in the system must not exceed 10 dB at 1.5 GHz.
Note: If you are using a different antenna please ensure the antenna gain combined with
the cable loss will provide sufficient signal strength for the ATS-6501.
D. If the location of the antenna dictates that a longer cable must be used then a line
amplifier will need to be inserted into the signal path or you will need to run an antenna
cable with less loss. A line amplifier is a device used to amplify the GPS signal to
overcome the losses resulting from longer cable runs. In selecting a line amplifier it is
necessary to make sure that it provides an adequate amount of gain and that it operates
from 1200MHz to 1600MHz.
E. The amount of gain required from a line amplifier can be calculated by knowing the total
loss of the antenna cables being used. The signal loss due to a cable varies depending
upon the frequency of the signal. For the purposes of GPS antennas the cable loss should
be calculated at 1500MHz. The manufacturer of the cable being used should be able to
provide an estimate of the cable loss at 1500MHz. Once the cable loss is known it can be
inserted into Equation 2-1 to calculate the required gain of the line amplifier
_
(
)
MIN
Gain
dB
F. The MIN_Gain value in Equation 2-1 serves as the minimum gain required from the line
amplifier being used. It is possible to use amplifiers with a slightly higher gain than the
minimum value but it will not improve the performance of the system. Using amplifiers
with significantly higher gain values can also cause degradation of the GPS signal
because it overdrives the input of the GPS receiver.
G. Placement of the line amplifier is also a concern in a properly designed system. Placing
the amplifier too far from the antenna may cause unexpected degradation in the GPS
signal and the performance will remain poor. The best place for the amplifier is typically
half way between the antenna and ATS-6501. This allows the line amplifier to benefit
from any surge protection that may be installed near the antenna but is still close enough
to the antenna so as not to degrade the signal significantly. Figure 2-2 shows the block
diagram of a typical installation that requires a longer antenna cable.
consideration when installing the line amplifier is how it will receive power. Some
amplifiers are powered using a DC bias on the antenna cable and others are power from
_
(
/
100
Cable
Loss
dB
7
DOC06501_Revision F
ATS-6501 Users Guide
The unit requires a
* )
_
(
ft
Cable
Length
100
)
ft
12
Eq. 2-1.
Another
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