10 Uses for an Antenna AnalyzerThe SARK100 antenna analyzer is a useful tool for the amateur radio station or the
homebrewer’s workbench. This section will describe the basic uses, as well some advanced
techniques for which you can use the analyzer to get intermediate measurements in order to
compute the desired result.
10.1 Antenna Measurements
The antenna is simply connected to the analyzer RF output and the analyzer is set to the desired
frequency. The instrument measures the SWR, impedance, resistance, and reactance. The
SCAN function will be helpful to automatically find the resonance frequency and the bandwidth of
the antenna.
10.2 Measure Feed Point Impedance
Connecting the analyzer directly at the antenna terminals or remotely through a halfwavelength
of transmission line allows direct measurement of the antenna terminal impedance. This is often
useful with vertical antennas.
A matching network can be connected to the antenna and then adjusted for best SWR on the
analyzer.
10.3 Measure Ground Losses
With short vertical antennas, measuring the impedance directly at the feedpoint allows
estimation of ground loss or loading coil loss. For example a ¼ wave vertical will have a
resistance of about 36 ohms at resonance. Any higher reading indicates ground loss.
Similarly shorter antennas (when resonated) will have lower resistance values. Reading a good
SWR may mean excess loss and measuring the actual impedance allows gauging just how
much loss.
10.4 Adjust Antenna Tuners
The analyzer can be used to adjust an antenna tuner for a perfect match without the need to
transmit a strong signal from the station rig. The analyzer uses only milliwatts of power lessening
the possibility of causing interference, see Figure 8.
10.5 Capacitor Measurement
There are several ways to measure capacitance with the SARK100. The simplest is to connect
the capacitor across the RF output connector and select Capacitance from the Mode pushbutton
menu. You can accurately measure capacitance values as long as the reactance at the
measurement frequency is within the impedance measurement specifications of the analyzer
(about 10 to 2000 ).
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