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Remarks:
• Place C1 to C5 (here: 0.1µF) close to MAX3232. For capacity values see
datasheet of actual component used.
• Use 3.3V level shifter (MAX3232 or equivalent).
• External antenna input impedance is 50 Ω. Match as close as possible.
3.2 Antennas
Generally, the quality of the GPS&GLONASS antenna chosen (passive or active) is
of paramount importance for the overall sensitivity of the GPS&GLONASS system.
Losses through a bad antenna, long cables or tracks or a bad antenna position can't
be compensated afterwards!
3.2.1 Passive Antennas
The A5100-A supports passive antennas via an integrated LNA directly.
3.2.2 Active Antennas
The A5100-A also supports active antennas directly, i.e. by offering an antenna
voltage feed pin (VANT – pin 9). It is recommended to use an active antenna with a
supply voltage of 3 to 5 VDC and a maximum current draw of 50 mA. The antenna
should have a gain ≥ 15dB but the total gain (antenna gain minus cable loss at the
antenna input of the module) should not exceed 30 dB. The noise figure should be ≤
1.5dB.
V1.0-Mar-14
RS232 Out
RS232 Out
1
1
6
6
2
2
7
7
3
3
8
8
4
4
9
9
5
5
Figure 7: RS232 level shifter
RS232 Level Shifter
RS232 Level Shifter
C1+
C1+
Vcc
Vcc
V+
V+
GND
GND
T1O
T1O
C1-
C1-
C2+
C2+
R1I
R1I
C2-
C2-
R1O
R1O
V-
V-
T1I
T1I
T2O
T2O
T2I
T2I
R2I
R2I
R2O
R2O
MAX3232
MAX3232
User's Manual
3.3V
3.3V
Tx
Tx
Rx
Rx
GND
GND
Page 15 of 43
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