PRODUCT NOTE 7106
GRE A
MERICA
, Inc. 425 Harbor Blvd. Belmont, California 94002 phone (650) 591-1400 fax (650) 591-2001
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has a grounded matching network for added protection. [NOTE: The PolyPhaser Corp. offers an excellent
application guide regarding lightning protection.]
The antenna is usually mounted by “U” bolts, with polarization either vertical or horizontal. Vertical is typical
for wireless, although sometimes horizontal is used to reduce interference. Either will work, but the polarity
must be the same at each end of the link for successful operation. Point the antenna as near as possible
toward the far end of the path.
When routing the coaxial cable, leave a service loop at the antenna so there will sufficient length of cable to
replace a faulty connector, when necessary. Secure the coax so that there is no mechanical stress at the
antenna connection. Follow the super structure with the cable to its base to the building. If the cable requires
suspension from the base to the building, use a stranded wire to support the cable weight. (The support will
prevent a migration of the cable's inner conductor to the shield.) Upon entering a building, leave a drip loop
so that water will not follow the cable inside. If the cable lays on a roof or the ground, protect it with a
conduit to guard against crushing. Inside, at the radio, use a short flexible patch cable, with the appropriate
fittings, from the radio to the main coaxial run for stress elimination at the radio's SMA connector. An
electrical test should be performed. After the test, water-proof all outdoor fittings, the ground connections,
and the cable entry points into the building.
TESTING
When the mechanical installation is completed, a Voltage Standing Wave Ratio “VSWR” test
should be done to determine that all electrical connections are correct and that the antenna is properly
matched. A test instrument called an inline wattmeter is connected between the radio and the coaxial cable
going to the antenna. The transmitter is turned on and its output power is measured on the meter. Next, the
reflected power or “VSWR” is read, it must be less than 5% of the transmitter power to be acceptable. Each
radio site will be checked in this way. If the “VSWR” is acceptable and the antennas are pointed correctly, the
link is ready to be tested using data. The data can be two computers using G-TALK, two terminals, any device
that will send back “known” information when polled “a DGH module” a Bit Error Rate Test set - called a
“BERT” [or just put the system on line and see if it works!].
RS232 DATA
The GINA 5000 RS-232 port is wired DCE to accept DTE with the transmit, receive data,
and CTS lines being active. The data flow and transmit functions are controlled internally by the radio in a
half duplex mode.
The GINA 6000 (X.25 packet) is also wired DCE, operating in a half duplex mode, but the RTS and CTS are
active along with the transmit and receive data lines. Before a “connect” can be initiated, it is necessary to
make RTS high. One way to do this, with limited “hardware” data flow control, is to disconnect the DTE RTS
wire and strap the CTS and RTS pins together at the DB9 interface. (Pin 7 to 8 additional flow control is
accomplished by the Xon/Xoff commands which are supported in the “firmware.”)
Using the VOICE OPTION, if it is installed, is a push-to-talk and release-to-listen operation, the same as in
other two-way radio communication. A bonus with this option is the convenience of easy transmitter keying
for RF testing.