VHF Transmitter Ampli
fi
er Instruction Manual
IM21-VT3150AMP
1
GENERAL
INFORMATION
Introduction
The VHF Transmitter Ampli
fi
er provides the
fi
nal stage of RF ampli
fi
cation and
fi
ltering for
the entire VHF Transmitter VT-3 132 - 174
MHz family and the VT-4 P25 Digital VHF
Transmitters. The ampli
fi
er has two distinct
frequency ranges: 132 to 150 MHz, and 150 to
174 MHz with continuously adjustable 2.0 to 8.0
Watts output power. This Ampli
fi
er is housed in a
machined aluminum case that ensures optimum
RF shielding, provides a good ground, and also
acts as a heatsink.
Additionally, the VHF Transmitter Ampli
fi
er is
equipped with output power and VSWR sensing
lines that can be individually con
fi
gured as open
collector or linear outputs. The internal VSWR
sensor protects the ampli
fi
er from high antenna
VSWR by approximately halving the ampli
fi
er’s
RF gain when a VSWR overload condition is
present.
The Lowpass Filter Board provides output
fi
ltering for the VHF Transmitter Ampli
fi
er.
The Lowpass
fi
lter assembly is mounted in a
separate compartment of the ampli
fi
er case
in order to provided maximum attenuation of
harmonic and other spurious signals.
