Deepace KC901M User Manual page 29

size more than 20 times of the wave length; generally the flat roof is acceptable to
test antennas whose frequency bands are over UHF.
Equipment: Two antenna stands, one has a turntable on the top. Antenna stands'
heights should correspond with the functional design of the antenna, normally it
should be larger than two operating wavelengths. The distance between the two
stands should be longer than 10 times of the operating wavelength (it is also
acceptable a shorter distance when testing antennas whose operating wavelengths
are exceptionally long, like short-wave antenna). Additionally, to remove the effects of
ground reflection, execute multiple testing at various distances so as to obtain the
average value among the results. Prepare a cable long enough to fit in the distance
between the stands, also allow a distance (between the operator and the instrument)
of at least 10 times of the wavelengths. Besides a tested antenna, a directional
antenna may be needed. To test the antenna gain, prepare another reference
antenna whose gain is already known.
Method: install the testing antenna and the antenna under test on the stand
(Chart 4-3). Testing antenna's main lobe should align with the antenna under test. In
specific, the first step is to align the under-the -test antenna's certain direction (a
predicted main-lobe direction or just mark a direction) with the testing antenna.
Secondly, set the instrument to mode S21 and enter the testing frequency. Commonly
choose a smaller span, 1MHz for example. Perform the user calibration in S21 mode
to make the curve return to zero. Rotate the under-the-test antenna within a certain
angle and record the corresponding S -parameters (dB) of every angle. Finally, mark
the points on the angle-gain coordinate graph to get the directivity diagram of the
under-the-test antenna.
The measurement mentioned above can also be done in insertion loss mode.
Firstly, enter
into the
measurement. Then press Auto CAL to make the insertion reading return to zero. Its
insertion reading shares the same meaning with the S
Chart 4-3: Measuring Antenna Gain in an Open Field
FIELD mode and choose Insertion to start the insertion
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parameter in S21.
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