User Manual

5 Ch. VHF Radio Repeater Equipment
Document Number 50-189201HBK – Issue 1 Page 17 of 48
4.5. BDA VHF Channel Shelves (50-189202 to 50-189206)
Rack 1 contains five Channelised Amplifier shelves, one shelf for each channel.
Each shelf is composed of identical sub-modules, the only differences being the frequency that the
modules are configured to pass and the part numbers of the crystal filters employed.
Each shelf is powered by a 24V DC feed from the PSU (50-146512) and has alarm outputs.
Shelf 1, 50-189202, passes channel 1
Shelf 2, 50-189203, passes channel 2
Shelf 3, 50-189204, passes channel 3
Shelf 4, 50-189205, passes channel 4
Shelf 5, 50-189206, passes channel 5
In the downlink direction, signals are received from the Downlink Input Splitter (50-189207) and pass
through a low noise amplifier, one of the two switched attenuators and a second LNA. After the
second LNA the signal passes into the channel selectivity module and then into a third LNA. After
vthe third LNA the passes through the second switched attenuator and then into a crystal filter which
further defines the operating frequency. After the crystal filter the signal passes through a 10W power
amplifier and then a ferrite isolator which provides isolation from reflected uplink signals. After passing
through the ferrite isolator the signal leaves the Channelised Amplifier shelf and enters the Downlink
Output Combiner (50-189208)
In the uplink direction, signals are received from the Uplink Input Splitter (50-189210) and pass
through a low noise amplifier, one of the two switched attenuators and a second LNA. After the
second LNA the signal passes into the channel selectivity module and then into a third LNA. After
vthe third LNA the passes through the second switched attenuator and then into a crystal filter which
further defines the operating frequency. After the crystal filter the signal passes through a 5W power
amplifier and then a ferrite isolator which provides isolation from reflected downlink signals. After
passing through the ferrite isolator the signal leaves the Channelised Amplifier shelf and enters the
Uplink Output Combiner (50-189209)
4.5.1. BDA VHF Channel Shelves Major Components
Parts common to all 5 shelves
Component
Part
Component Part Description Qty Per
Assembly
08-930002 2 Port Isolator 2
10-000701 Switched Attenuator 0-30dB 0.25W 2
10-000901 Switched Attenuator 0-15dB 0.25W 2
11-006002 LNA VHF 70-500MHz with Relay 5
11-007602 LNA 50-200MHz (HIGH IP3) 1
12-002201 3 Stage Amplifier Alarm Board 2
12-004902 Power Amplifier VHF 5W 1
12-005201 Power Amplifier VHF 10W 1
13-001803 Dual D/DC Convertor 24V-12V 1A 2
17-010810 VHF Channel Selectivity Module 2
19-000922KL 3U Rack Mount Chassis 1
20-001601 12V Relay PCB Assembly 1
80-008902 24V Relay PCB Assembly 1
80-008909 12V Relay PCB Assembly with LED 1