User Manual

Unit 5 – 250W Amplifier
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5. 250W amplifier:
5.1. Function:
Its function is to amplify the power that comes from 1:4 divisor to the 250W output level.
5.2. Technical characteristics:
Power supply: ________________________________________________________________ 32Vdc 20 A maximum
Output power:____________________________________________________________________ 250W (Peak Sync)
Gain: ________________________________________________________________________________________ 18 dB
Setting Temperature: __________________________________________________________________________ 56°C
5.3. Technical Description:
The UHF 250W amplifier is formed by the combination of two 125W amplifiers.
At the input and output there are two 3 dB hibrid couplers with the rejection loads R1 and R14.
The signal splitted by the input 3 dB coupler feeds the two 50W amplifiers through C1 and C2.
At the input of each 50W amplifier there is a balun L1 and L2 that splittes the signal again for
two transistor Q1, Q2 and Q3, Q4 respectively.
The amplified signals through the baluns L5 and L6 are combined in the final 3 dB coupler with
the coupling capacitors C28 and C34.
The bias circuit is formed by resistores R12, R13 and zener diode D3 that generates a +15Vdc.
Through trimpot’s R6 and R7 the bias voltage for the transistor’s gate are adjusted.
The diode D1 and D2 allows a protection, for the amplifier, reducing the bias voltage and the
gain of the amplifier.