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g.
From the supplied Antenna Acceptance Data sheet, obtain the loss value between the dual feed
assembly and the test antenna output. The test antenna is calibrated at 2700, 2800 and 2900 MHZ.
For operating frequencies other than these, interpolation is required.
h.
Add the loss value (step g.) to the measured value (step f.) to obtain the average power output of the
radar system. A 1000 Watt output corresponds to 60 dBm.
Because the loss value obtained in step g. is slightly frequency sensitive,
operate only one transmitter at a time for the most accurate measurement.
5.1.3 Circular Polarization Check - The following steps describe the procedure to check circular
polarization.
a.
Switch the antenna to circular polarization.
b.
Connect the test antenna load to the coupled port and a power meter thermistor mount to the through
port of the test antenna directional coupler.
c.
Inject at least 10 mW of power into the input of the feed to be tested. This can be done by opening
the waveguide run at any point and attaching a waveguide to coax adapter to the antenna input. The
signal generator can then be connected to the adapter.
d.
Loosen the three clamp screws on the test antenna so the antenna can be rotated with slight
resistance.
e.
Rotate the test antenna to obtain a maximum reading on the power meter. Record the reading.
f.
Note the angular position of the test antenna. Also note whether the antenna as viewed from the rear
is rotated clockwise or counterclockwise relative to its 0 degree position.
g.
Rotate the antenna to obtain a minimum value on the meter. Record the reading.
h.
Using the dB calibrations on the meter scale, note the dB difference between the maximum and
minimum values. This is the axial ratio.
i.
Consult the supplied Antenna Test Data Sheet, to obtain factory measured values. Differences in
measured values of several degrees in angular position may be observed since the exact peak value is
difficult to obtain for small axial ratios. Axial ratio should be within 1.0 dB of the factory value.
NOTE
80
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