User's Manual
Active GPS antenna Standard Wave Ratio (SWR) test
SWR test
The RF signals from the GPS satellites are extremely low-level microwave signals that
must reach the RFTG with minimal distortion and loss. To verify the RF integrity of the
complete antenna and cable system, a Standing Wave Ratio (SWR) or Distance-to-Fault
(DTF) test should be performed.
Since the GPS antenna is an active device, a standard SWR or DTF test setup cannot be
used. A Bias-T must be employed to inject +5 VDC into the RF line to power the
antenna's Low Noise Amplifier (see Figure below).
Important! The antenna will meet it's specified SWR only when powered in this way.
Calibrate the Wiltron as shown and per the manufacturer's instructions. Perform the SWR
or DTF measurement as shown and per the manufacturer's instructions. Record the MAX
SWR indicated and/or DTF data. If it MAX SWR is greater than 2.5, the fault must be
repaired and the antenna and cable retested.
Bias-T
Mini-Circuits
ZFBT-4R2G-FT
GPS
Antenna
5VDC
Power
Supply
Wiltron Site
Master
DC
RF
Digi-Key
T309-ND
RF & DC
GPS Antenna Cable
Calibrate Wilton at
output of Bias-T
F1=1570.0 MHz
F2=1580.0 MHz
Antenna SWR spec.
MAX SWR = 2.5 (7.4 dB return loss)
Digi-Key (800) 344-4539
Mini-Circuits (800) 654-7949
GPS antenna installation Active GPS antenna Standard Wave Ratio (SWR) test
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9927 Dist BTS Outdoor
401-703-516
Issue 1 March 2012
Alcatel-Lucent – Proprietary
Use pursuant to applicable agreements
E-15