User's Manual

Navini Networks, Inc. Ripwave Base Station I&C Guide
61
Omni Antenna
An Omni antenna has 2 degrees of fixed electrical downtilt
Set the Azimuth
Position the RFS on the mounting pole or structure, ensuring that the antenna is pointing in the
proper azimuth direction determined by the engineering study. For an omni, the first antenna
element must face East (Figure 30).
The azimuth direction is stated in degrees from true North. Use the diagram shown in Figure 31
to determine the declination angle for your location. Add or subtract the declination angle from
magnetic North to obtain true North.
Tighten the four nuts on each of the two antenna mounting brackets to secure the RFS to the
mounting pole. Use a compass to check the direction from the center of the panel (this is
magnetic North). Be sure that you are using a compass calibrated for the geographical region
where you are. There are five such regions and a compass calibrated for one of them will not
work properly in the others.
Since this is not the year 2000 anymore, you will want to check this reference map to learn how
your magnetic declination shifts from year to year. Notice that the map measures annual shifts in
minutes. Since it takes 60 minutes to equal 1 degree, if you notice that your location has a
declination shift of 5 minutes per year, this means it will be another 12 years before your
declination adjustment changes by one whole degree. The following web site provides more
details on how to use these charts: http://www.thecompassstore.com/decvar.html
Verify the Downtilt
Using an inclinometer (Figure 32), check the downtilt of the RFS antenna. If required, adjust the
angle using the downtilt adjustment brackets. Be sure to include any electrical uptilt or downtilt
built into the antenna in the setting.
Tighten the mounting hardware to secure the RFS in the proper position. Recheck the downtilt
angle again to verify proper position. Repeat the procedure for all other antennas that are
installed in the system. Ensure that they are mounted in the proper direction and with the correct
downtilt angle.
Install Surge Protectors
If lightning protection is required, as determined by the customer, the power/data lightning
arrestors must comply with UL497. Cables, such as the RF and power/data cables, in excess of
140 feet in length must have protective devices installed that are UL497A or UL497B listed.