User's Manual

22 MDS 9810 Installation and Operation Guide MDS 05-3301A01, Rev. C
Invisible place holder
Figure 18. Data Interface Cable Wiring for Tail-End Links
Programming
In a tail-end link system, the radio’s device behavior must be set to
DEVICE CTS KEY (Page 38) using the HHT. This allows one radio to
control the keying of another. Also, the CTS delay time must be set
(using the
CTS xxx command, Page 37) to the time required for the
other transceiver to key up. This time is typically 10 ms for MDS
2000/4000 series transceivers.
4.4 Repeaters—Traditional Method
Two MDS 9810 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 sta-
tion antennas. A detailed discussion on the effects of terrain is given in
Section 3.2, Site Selection (beginning on Page 8).
The following paragraphs contain specific requirements for repeater
systems.
DB-25 DB-25
MDS 2000/4000 Series XCVR
(or device requiring keyline)
2
3
7
3
2
7
MDS Spread Spectrum
Remote XCVR
(DEVICE CTS KEY)
TXD
RXD
GND
RXD
TXD
GND
54
CTS RTS
Keyline
DCE
DCE