Operations Manual

INSTALLATION 3-1
O&M of the MCC-545B PACKET DATA RADIO
12/2000
3.0 INSTALLATION
This section provides general information on site selection and installation of the 545B, as well
as 545B power-up procedures.
3.1 Site Selection
One of the most important considerations in the proper operation of the MBCS is the selection of
the 545B-operating site. There are a number of factors, which influence selection:
1. External Noise/Interference
2. Horizon angle
3. DC power source
4. Site dimensions
5. Antenna considerations
3.1.1 External Noise/Interference
Noise and signal interference can reduce the performance of the 545B. There are several sources
of interference; following are the most common sources:
! Cosmic Noise
! Power Line Noise
! Auto Ignition Noise
! Computer-Generated Interference
! External Signal Interference
Cosmic Noise
Cosmic noise is the limiting noise factor in a meteor burst system, especially in the low
frequency band (40-50 MHz). The noise is generated by star systems in the galaxy and is
frequency dependent. The noise is approximately 15 dB above thermal at 40 MHz, and 13 dB
above thermal at 50 MHz. The noise is also diurnal in nature, being the highest when the
antennas are pointed directly at the center of the galaxy and lowest when they are pointed at right
angles to it. Daily variations of 3 to 4 dB are to be expected. An optimal meteor burst site is one
that is limited only by cosmic noise.
The 545B STAT command is very useful in determining the site antenna noise levels. Since the
Receiver has an IF bandwidth of 13 KHz, the STAT reading should read from –120 to –115
dBM if the Receiver to antenna line loss is about 1 to 2 dB (100-200 ft of RG-214). The noise
blanker is not effective for cosmic noise, so the noise readings are the same whether the blanker
is on or off.