Daniels VT-3/140-SWA2, Instruction Manual

Page: 135 / 262

VHF Amplifier Instruction Manual VT-3 132 - 174 MHz 1-1
1 GENERAL
1.1 Introduction
The VT-3/150 Amplifier provides the final stage of RF amplification and filtering for the entire
VHF Transmitter VT-3 132 - 174 MHz family. The amplifier 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.
The VT-3/150 Amplifier is housed in a machined aluminum case that ensures optimum RF
shielding, provides a good ground, and also acts as a heatsink.
Additionally, the VT-3/150 Amplifier is equipped with output power and VSWR sensing lines
which can be individually configured as open collector or linear outputs. The internal VSWR
sensor protects the amplifier from high antenna VSWR by approximately halving the amplifier's
RF gain when a VSWR overload condition is present.
Output filtering for the VT-3/150 Amplifier is provided by the VT-3/150 Lowpass Filter Board.
The lowpass filter assembly is mounted in a separate compartment of the amplifier case in order to
provided maximum attenuation of harmonic and other spurious signals.
Refer to Section 4 for the VT-3 132 - 174 MHz VHF amplifier and lowpass filter component
layouts and schematic diagrams
1.2 Performance Specification
Type: MT-3 series VHF Amplifier module.
Compatibility: MT-3 series Transmitter Main Board.
Frequency Range: 132 MHz to 150 MHz or 150 MHz to 174 MHz.
RF Power Output: adjustable 2.0 to 8.0 Watts
RF power Input: nominal level adjustable from +4 dBm to +10 dBm,
held /- 2 dB of nominal.
Ouput Impedance and VSWR: 50
Ω
, Type N connector; 3:1 max. VSWR.
Input /Output Isolation: > 60 dB
Duty Cycle: 100%: Continuous operation from -40˚ C to +60˚C.
Harmonic Emissions: Less than -80 dBc .