DE
DANIELS
ELECTRONICS
2-2
UHF Amplifier Instruction Manual UT-3 406 - 512 MHz
2.2
Power Requirements
Typical current requirements for the UT-3/400 Amplifier at different power levels are given in the
Table 2-1 below. The current drawn from the +9.5 Vdc supply should never exceed 1.2 Amps
and the current drawn from the +13.8 Vdc supply should never exceed 1.5 Amps.
Table 2-1
UT-3/400 Amplifier Current Consumption
0.5 to 2.0 Watt Amplifier
2.0 to 8.0 Watt Amplifier
Output
+9.5 Vdc
Output
+9.5 Vdc
+13.8 Vdc
Power
Supply Current
Power
Supply Current Supply Current
0.5 W
0.65 A
2.0 W
0.64 A
0.51 A
1.0 W
0.87 A
4.0 W
0.79 A
0.75 A
1.5 W
1.02 A
6.0 W
0.89 A
0.93 A
2.0 W
1.17 A
8.0 W
1.04 A
1.10 A
Note: Current consumption measured at 470 MHz
2.3
RF Circuitry
The RF circuitry consists of several blocks: a 5 dB input pad (R1, R2, and R3), an RF amplifier
module (U4), an output power boosting transistor (Q1), three directional couplers (TL1, TL3, and
TL4), and the UT-3/400 Lowpass Filter. The heart of the UT-3/400 Amplifier is RF amplifier
module U4. This module amplifies a 1 mW signal up to a maximum of 2.0 W, at the antenna
connector, for a low power unit. In high power units, the output of U4 is further amplified by Q1
to a maximum of 8.0 Watts at the antenna connector. Capacitors C17 and C24 provide tuning for
transistor Q1's input and output match. Although the input match and the output match for Q1 are
tunable, the networks have been made broadband so that the high power amplifiers will operate
over the same frequency range as the low power amplifiers. The frequency band of the UT-3/400
Amplifier is determined by the operating frequency range of the RF amplifier module U4.
Directional couplers (TL1, TL3, and TL4) are used to sample forward and reverse power. The
sampled power is used by the sensing and power control circuits to control the amplifier's
operation. The final step in the RF path is output filtering and, as mentioned earlier, this is done by
the UT-3/400 Lowpass Filter.
2.3.1 UT-3/400 Lowpass Filter
The UT-3/400 Lowpass Filter is a 50 ohm, 9 pole, reciprocal filter with a 3 dB cutoff frequency of
approximately 512 MHz. The lowpass filter assembly attenuates the desired signal's harmonics as
well as any other out-of-band emissions so that a 'clean' RF signal is output to the antenna
connector.
