User's Manual

05-3946A01, Rev. C TransNET OEM Integration Guide 31
in order to reduce the interference to the point where overload of one network
by the other will not occur. The
CSADDR command will provide relief from
this antenna separation requirement by operating the networks in a TDD
mode and ensuring that one Master cannot transmit while the other (or
multiple others) are trying to receive a signal from a distant radio.
Master Station Configuration
On all Masters for which you wish to synchronize transmissions, establish
one Master as the “Clock-Sync Master by setting its
CSADDR value to it own
Network Address (
ADDR xxxxx). Then, set all other dependent Masters
CSADDR values to the Network Address (ADDR) of the Clock-Sync Master.
Make sure that you use a different Network Address (
ADDR) for each Master.
This value will be used to identify all units associated with this Master’s
network.
Note that all Masters must be set to the same
CSADDR setting, but only one
where the CSADDR matches its own ADDR; this is the Clock-Sync Master.
CSADDR = ADDR —Unit serving as a Clock-Sync Master
CSADDR ¦ ADDR —Unit serves as a Dependent Master (Clock Slave)
CSADDR = NONE —Co-located Master feature disabled (default)
HOPTIME, FEC and SAF values are provided by the Clock-Sync Master to all
dependent units.
NOTE: If a Dependent Master station is unable to find the Clock-Sync Master station, it will not
be able to operate properly and the associated network will be out-of-service.
Antenna System for Co-Located Master Stations
Using this TDD (Clock-Sync) mode will prevent any two Masters from trans-
mitting at the same time and greatly reduce the antenna separation require-
ments to near zero. Under this arrangement, the antennas of co-located
Masters may be placed a few feet (less than a meter) apart horizontally, or just
above or below vertically with no ill effects. There are two common antenna
system arrangements:
Sharing a Common Antenna System
It is possible to share an antenna between multiple Masters using stan-
dard power dividers, as long as the extra loss associated with these
devices is taken into account in your RF “budgeting” process. Masters
in this configuration must be operating with Clock-Sync (
CSADDR)
enabled.
For example, the two Master stations shown in Figure 15 are connected
to a common antenna system. They use a power-divider that will result
in a signal loss of 3 dB, or one-half power level, on both transmit and
receive signals.
The power divider, such as a Mini-Circuits ZAPD-1 or similar product,
must be capable of handling 1 Watt and have >25 dB isolation between
TX ports.