User Manual

Axell Wireless Limited
Technical Literature
L.A. M.T.A. Remote Sites
Document Number 80-301401HBKM Issue No. 1 Date 13/06/2008 Page 97 of 148
4.9. VHF Amplifier Shelf 80-301409
VHF Amplifier Shelf 80-301409 provides the amplification stages for the VHF paths, The unit is
housed in a 4U, 19” rack mount shelf which is mounted in Rack 1
The Downlink VHF signal is received at the port labelled “DOWNLINK I/P” (Annotated A in the picture
in section 4.9.4.2.). The Downlink VHF path passes through a bandpass filter to remove out of band
noise and then a switched attenuator providing 0 to 30 dB of RF signal attenuation.
After leaving the attenuator the VHF Downlink signal passes through a 5W amplification stage, this
amplification stage is straddled by an Automatic Gain Control assembly providing limiting to the output
signals in the case of high input signals.
After leaving the Amplification/AGC stage the VHF Downlink signal passes through a second
bandpass filter and exits the Shelf via the port labelled “DOWNLINK O/P” ( B in section 4.9.4.2.).
The Uplink VHF Signal is received at the port labelled “UPLINK I/P” (C in section 4.9.4.2.). The VHF
Uplink path passes through a bandpass filter to remove out of band noise and then a switched
attenuator providing 0 to 30 dB of RF signal attenuation.
After leaving the attenuator the VHF Uplink signal passes through a 5W amplification stage, this
amplification stage is straddled by an Automatic Gain Control assembly providing limiting to the output
signals in the case of high input signals.
After leaving the Amplification/AGC stage the VHF Uplink signal passes through a second bandpass
filter and exits the Shelf via the port labelled “UPLINK O/P” (D in section 4.9.4.2.).
VHF Amplifier Shelf 80-301409 is provided with a 24V DC input to power the amplifier modules within
and those amplifier modules are configured to provide alarm status reports.