User Manual

Table Of Contents
Mission Valley Radio Repeater Equipment + Upgrade
User/Maintenance Handbook
Handbook No. 50-078021HBKM Page 49 of 85
4.1.1 Description
The wall mounted tunnel BDA is a band-selective unit which draws its RF from the tunnel leaky feeder
coaxial cable, feeding separate down and uplink ports and operating in the 800MHz frequency region
with a cross-band coupled bypass to allow VHF signals to be passed through the amplifier with just a
small loss. (The loss at 800MHz is considerable compared with the VHF signals, so a small amount of
gain at 800MHz is required to overcome these losses, whereas the VHF signals need no boosting).
The primary application for the BDA is to boost the 800MHz and VHF signals in areas of the West
Tunnel and Fire Exits where coverage would otherwise be inadequate. Notice that each path has
automatic gain control as the amplifier receives its input from the leaky feeder antennas for both up
and downlink. This means that the signal could have large differences in level at any time which is
why the AGC is needed on both paths.
The amplifier needs 12V DC for its supply, and this enters from the BBU unit through a rugged
connector mounted on the R.H.S (viewed from front) of the case. For further notes on the use of the
battery backup system, see the dedicated BBU handbook at the end of this document (appendix B).
4.1.2 Electrical Specification
PARAMETER SPECIFICATION
855-869MHz (Downlink)
Frequency range:
810-824MHz (Uplink)
Bandwidth: 14MHz (both paths)
Rejection @ opposite band: 70dBc
Rejection @ 837.5MHz: 50dBc
Gain: >30dB
Gain Adjustment: 0 - 30dB (in 2dB steps)
Uplink 1 dB compression point: +37dBm
Downlink 1 dB compression point: +42dBm
Uplink +44dBm
IP3
Downlink +54dBm
Noise Figure: <8dB
+32dBm (uplink)
AGC level:
+33.5dBm (downlink)
VSWR: better than 1.5:1
RF Connectors: N type, female
Impedance: 50
Alarms Fitted:
(volt-free contacts)
1 Amplifiers