A3LA-R-MIL-MOD User Guide Version B
Document Number: 451-93156-001A
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3
A
NTENNA
C
ONNECTOR
The A3LA-R modem uses a single TNC female 50-ohm connector to both transmit and receive.
Cable loss between the modem and the antenna is critical and must be kept less than 3 dB at
the operating frequency of 1616 to 1626.5 MHz. The minimum link margin of 12 dB must also
be maintained. General RF parameters are listed in Table 2 below.
Table 2: General RF Parameters
Type
Description
Frequency Range
1616 to 1626.5 MHz
Input/Output Impedance 50 ohms
Oscillator Stability
± 1.5 ppm
NAL Research offers several types of antennas for use with the A3LA-R modem. These antennas
include the fixed mast, mobile magnetic/permanent mount, and portable auxiliary. For low cost
and applications where small form factor and light weight are required, NAL Research
recommends model SYN7391-C. If the specific application requires a custom antenna, it must
meet the specifications (see Table 3).
Table 3: Custom Antenna Specifications
Parameter
Value
Operating Temperature Range
–40°C/+85°C without loss of function
Measurement Frequency Range
1616 to 1626.5 MHz
VSWR
< 1.5 : 1
Maximum Gain
3 dBiC
Nominal Impedance
50 ohms
Polarization
Right-handed circular polarization (RHCP)
Basic Pattern
Omnidirectional and hemispherical
Satellite signal strength reported by the A3LA-R when issuing an AT+CSQ command indicates
the signal strength of the ring channel. Be careful when using this signal reading for
comparisons between devices. Of particular note are the following:
1.
There is a 0.5 dB tolerance on the calibration.
