User's Manual

MDS 05-2708A01, Rev. A MDS TransNET I/O Guide 17
Antennas Omnidirectional antennas are normally required at all stations in a
simplex system. The transmission range may be significantly
reduced as compared with stations using directional antennas, so it
is especially important that sites be chosen to allow sufficient signal
strength between all units. A discussion of site selection is provided
in Section 4.2.
5.3 Tail-End Links
A tail-end link is established by connecting an MDS TransNET 900 radio
“back-to-back” with another radio such as a licensed MDS 2300/4300 series
transceiver. This can be used to link an outlying remote site into the rest of an
MAS network. Here are some specific requirements for tail-end link systems:
Interface Wiring
The connection between the two radios in a tail-end link system
must be made as shown in
Figure 14.
Figure 14. Data interface cable wiring for tail-end links
5.4 Repeaters—Traditional Method
Two MDS TransNET 900 radios (or another MDS spread spectrum radio)
may be connected “back-to-back” using a null-modem cable to form a repeater
station. This is sometimes required in a network that includes a distant remote
station that would otherwise be unable to communicate with the master station
due to distance or terrain.
A repeater works by re-transmitting data from the outlying remote site to the
master station and vice versa. It introduces a small amount of end-to-end
transmission delay, but this is not a problem in most systems.
The geographic location of a repeater station is especially important. A site
must be chosen that allows good communication with both the master and the
outlying remote site. This is often on top of a hill, or other elevated terrain from
which both sites can be “seen” by the repeater station antennas. A detailed
discussion on the effects of terrain is given in Section 4.2, Site Selection
(beginning on page 8).
The following paragraphs contain specific requirements for repeater systems.