Codan Radio Communications VT-3A130-S-FSH User Manual
DE
DANIELS
ELECTRONICS
VT-3A130 Amplifier Instruction Manual
2-1
2
THEORY OF OPERATION
2.1
General
VT-3A130 Amplifier is a Class A linear amplifier with a low level AM modulator. A built in
regulated power supply provides approximately 15.0Vdc output voltage with the input voltage
range of 10.0 Vdc to 17 Vdc. This amplifier utilizes a 10 Watt hybrid power amplifier module
manufactured by Mitsubishi. The module is mounted directly to the heatsink with its leads soldered
to a circuit board where DC supply voltage and RF input and output connections are made.
regulated power supply provides approximately 15.0Vdc output voltage with the input voltage
range of 10.0 Vdc to 17 Vdc. This amplifier utilizes a 10 Watt hybrid power amplifier module
manufactured by Mitsubishi. The module is mounted directly to the heatsink with its leads soldered
to a circuit board where DC supply voltage and RF input and output connections are made.
Power for the VT-3A130 Amplifier is provided from +13.8 Vdc and 9.5Vdc supplies. The
supplies can be continuously connected to the amplifier. The VT-3A130 Amplifier will draw only
about 4 mA of current from +13.8 Vdc and about 0.1 mA from 9.5Vdc until the AMPLIFIER
ENABLE pin is grounded.
supplies can be continuously connected to the amplifier. The VT-3A130 Amplifier will draw only
about 4 mA of current from +13.8 Vdc and about 0.1 mA from 9.5Vdc until the AMPLIFIER
ENABLE pin is grounded.
The VT-3A130 Amplifier is housed in a machined aluminum case that ensures optimum RF
shielding, provides a good ground, and also acts as a heatsink.
shielding, provides a good ground, and also acts as a heatsink.
2.2
Power Requirements
The current drawn from the +9.5 Vdc supply should not exceed 10 mA. Current consumption of
the +13.8 Vdc line is dependent on transmitter frequency, output power, temperature, and supply
voltage and can range from 800 mA to 1500 mA. The current drawn from the +13.8 Vdc supply
should not exceed 1500 mA under normal circumstances and should never be allowed to exceed
1700 mA.
the +13.8 Vdc line is dependent on transmitter frequency, output power, temperature, and supply
voltage and can range from 800 mA to 1500 mA. The current drawn from the +13.8 Vdc supply
should not exceed 1500 mA under normal circumstances and should never be allowed to exceed
1700 mA.
2.3
RF Circuitry
Refer to Section 4.1.2 "VT-3A130 Amplifier Schematic Diagram". The RF input signal with a
level of -5 dBm to +5 dBm is fed to the VT-3A130 Amplifier Board and then is modulated by a
balanced AM Modulator which consists of Q1, Q3, Q4, and a wide band RF transformer XFMR1.
Q1, Q3 collectors are supplied by 15.0 Vdc in order to increase the modulation linearity. On the
contrary, the base circuitry of Q1, Q3 and Q4 are biased by 9.5 Vdc. The typical output power
from the Modulator is about 3dBm to 5 dBm. The signal is then amplified further by a Hybrid
Power Amplifier Module U1, which is the class A, 10 watt linear amplifier. The U1 is supplied
from a 15.0Vdc internal regulated power supply. Maximum carrier power output is 4 - 5 watt for
the input voltage range from 10 Vdc to 17 Vdc. Output filtering for the VT-3A130 Amplifier is
provided by a Low Pass Filter Board. The Low Pass 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 4.1.1 "VT-3A130 Amplifier Component Layout"
level of -5 dBm to +5 dBm is fed to the VT-3A130 Amplifier Board and then is modulated by a
balanced AM Modulator which consists of Q1, Q3, Q4, and a wide band RF transformer XFMR1.
Q1, Q3 collectors are supplied by 15.0 Vdc in order to increase the modulation linearity. On the
contrary, the base circuitry of Q1, Q3 and Q4 are biased by 9.5 Vdc. The typical output power
from the Modulator is about 3dBm to 5 dBm. The signal is then amplified further by a Hybrid
Power Amplifier Module U1, which is the class A, 10 watt linear amplifier. The U1 is supplied
from a 15.0Vdc internal regulated power supply. Maximum carrier power output is 4 - 5 watt for
the input voltage range from 10 Vdc to 17 Vdc. Output filtering for the VT-3A130 Amplifier is
provided by a Low Pass Filter Board. The Low Pass 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 4.1.1 "VT-3A130 Amplifier Component Layout"