DE
DANIELS
ELECTRONICS
UHF Amplifier Instruction Manual UT-3 406 - 512 MHz
3-3
amplifier's output power level, alarm levels, and tuning for the transistor matching circuit in the
high power version can be set without detaching the amplifier from the transmitter board.
However, if the output power alarm or the Antenna VSWR alarm output configuration requires
changing, the UT-3/400 Amplifier must be detached from the MT-3 Transmitter Board. Refer to
section 4 page 2 "UT-3/400 Amplifier Component Layout" for the location of solder jumpers JU1
to JU5.
3.6.2 UT-3/400 Amplifier Adjustment
The Amplifier alignment consists of two adjustment procedures; (i) a general set up (section
3.6.2.1) procedure which sets up the proper bias conditions for the RF transistors and (ii) the RF
threshold adjustments which set up the desired alarm threshold levels as well as the RF output
power. The general alignment procedure is required following major repair operations, changes in
RF input levels or large changes in operating frequency (greater than ± 1.0 MHz).
The RF output and alarm threshold level adjustments are more easily accessible so that fine
adjustments can be made in the field. Depending on user requirements, the RF alarm threshold
levels should be checked whenever a significant change in operating frequency (± 0.5 MHz) is
made. As the antenna VSWR alarm is dependent on the output power alarm, the output power
alarm should always be set first. The order of adjustment should be:
The adjustment procedures for the high power and the low power version amplifiers are identical
after the matching for transistor Q1 is tuned in the high power version. As the antenna VSWR
alarm is dependent on the output power alarm, the output power alarm should always be set first.
The order of adjustment should be:
1)
High Power Amplifiers Only — Tune the transistor matching circuit at the
desired frequency and power.
2)
Set the desired output power alarm level (section 3.6.2.2).
3)
Set the desired output power level (section 3.6.2.3).
4)
Set the desired Antenna VSWR alarm level (section 3.6.2.4).
5)
Set the desired overload condition level (section 3.6.2.5).
Details for the preceding four steps are outlined below.
3.6.2.1
General Set-Up
1
Connect the transmitter's antenna output connector to the type N input of the radio
communications test set through a short section of low loss 50
Ω
coaxial cable.
2
Turn all four (4) of the adjustment potentiometers (R7, R21, R36, and R38) fully
counterclockwise.
