Preparing The Equipment For Vhf Alignment; Tuning The Vhf Preselector - Motorola ASTRO 25 GTR 8000 Manual

5.9.1.1.2
Calculating The VHF Alignment Frequency for Multiple Receive Frequencies
When and where to use: For base radio with multiple receive frequencies, calculate the frequency of
the alignment signal as follows:
Procedure:
1 From the site documentation or the Configuration/Service Software (CSS), note the receive
frequency for each channel.
2 Calculate a midpoint frequency as follows:
F = (F + F
mid highest
3 Using F in place of the receive frequency, perform steps 3 and 4 from
mid
Alignment Frequency For a Single Receive Frequency on page
5.9.1.2

Preparing the Equipment for VHF Alignment

Perform the following procedure to prepare the equipment for VHF alignment.
Procedure:
1 Ensure the base radio (with preselector assembly) is installed in a functional station cage
equipped with a power supply module.
2 Detune the preselector as follows:
a If the alignment frequency (calculated in
Single Receive Frequency on page 160
Multiple Receive Frequencies on page
(Range 2), turn the five tuning screws clockwise until 1/8 inch protrudes past each of the
tension nuts.
b If the alignment frequency is less than or equal to 148 MHz (Range 1) or 156 MHz (Range 2),
turn the five tuning screws counterclockwise until 3/4 inch protrudes past each of the tension
nuts.
3 Using the torque driver and deep well socket, tighten the five tension nuts on the adjustment
screws to 6 in-lb.
4 See Figure 59: Preselector Tuning — VHF on page
5.9.1.3

Tuning The VHF Preselector

NOTICE: When tuning for peak or dip, turn the tuning screw 1/2 turn past the peak or dip to
verify that you have obtained a true peak or dip. After you have found true peak or dip, turn the
screw back to the location of the original peak or dip.
See the figure for the location of the tuning screws and cavity probe holes.
) ÷ 2
lowest
Chapter 5: GTR 8000 Base Radio Optimization
160.
Calculating The VHF Alignment Frequency For a
or Calculating The VHF Alignment Frequency for
161) is greater than 148 MHz (Range 1) or 156 MHz
162.
MN003286A01-E
Calculating The VHF
161