6. VSWR
Before use, it is important to determine the antenna
system’s VSWR (voltage standing wave ratio). You
will need a high quality SWR bridge (meter) to
accurately tune your antenna system. First, make
sure the SWR bridge is in good working order and is
calibrated. To ensure your radio is performing
properly the VSWR should never exceed 1.5 to 1.
Never transmit on any antenna system where the
VSWR exceeds 1.8 to 1. This will stress the output
stage and could destroy the RF transistors; this type
of misuse and failure is not covered under warranty.
Measure the VSWR at the center of the operating
band. Tune the antenna (according to the antenna
manufacturer’s tuning instructions) so that the
VSWR is as close to 1 to 1 at the center of the
operating band.
Next, measure the VSWR at the lowest and highest
frequency of the transceiver. If the antenna has a
wide enough frequency range and band-pass, the
VSWR readings should be below 1.5 to 1 across the
entire operating band. If at the lower or upper end of
the transceiver operating frequency, the VSWR
measures more than 1.5 to 1, it is recommended
that the antenna be re-tuned before operating on
those frequencies.
If you are experiencing unusual VSWR readings
check for the following possible problems:
1) Make sure that the antenna is installed properly
and grounded.
2)
Check all coaxial cable and connectors for
defects and poor routing.
3) If testing a vehicle installation, make sure that all
vehicle doors are closed when testing.
4) Do not test near or around large metal objects or
buildings.
7. Ignition Noise
In certain vehicle installations, electrical noise or
interference may be present in the receive audio of
the transceiver. Typically the vehicle’s ignition
system or more specifically the alternator generates
this noise. The Raptor is equipped with both ANL
and noise blanker circuits that are designed to
improve, and in many instances eliminate, electrical
noises.
In extreme cases, the noise blanker may not
eliminate all electrical noises. In such cases, an
inline DC noise filter can be used. The XLF-20
FilterCord by RF Limited is designed for use with the
Raptor and is an effective way to eliminate all noise
emanating from the 12VDC line. The filter will not
have any effect on airborne noise entering the radio
through the antenna system. This includes the
‘popping’ sound associated with ignition systems.
Summary of Contents for Raptor
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