Palstar ZM-30, Owner'S Manual

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The ZM-30 antenna analyzer is an extremely
useful instrument to have around the ham
shack or homebrewer’s workbench. This
section describes the basic uses, as well as
some advanced techniques for which you can
use the analyzer to get intermediate
measurements in order to compute the desired
result.
Antenna Measurements
The antenna is simply connected to the
analyzer antenna terminal and the analyzer is
set to the desired frequency. The readout
gives the resultant SWR, impedance,
reactance and resistance. If the frequency is
tuned across a ham band, the minimum SWR
point (resonance) can be found as well as the
SWR end points (usually 2:1) yielding the
bandwidth of the antenna system. See Figure
7.
Measure Feed Point Impedance
Connecting the analyzer directly at the
antenna terminals or remotely through a half-
wavelength 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.
Measure Ground Loss
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.
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 5.
Capacitor Measurement
There are several ways to measure capacitance
with the ZM-30. 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-1000 ohms).
Another way to measure capacitance with the
ZM-30 is to measure it in a series resonant
circuit. (See as Figs 1 and 6). You will need
an inductor of known value and a 51-ohm
carbon composition or film resistor. It is
recommended that a small 5% tolerance choke
with an inductance of between 1 and 10 uH be
used. Common RF chokes are fine and can
be obtained from most full-service mail order
component suppliers.
To measure capacitance by the second
method, connect the components as shown in
Figure 1. Then adjust the operating frequency
for lowest SWR and record the frequency.
Now you can calculate the capacitance using
the formula:
C = 25330/(F*F*L)
where C is the capacitance in picofarads, F is
the frequency in MHz and L is the inductance
in microhenries.
Inductor Measurement
There are several ways to measure inductance
with the ZM-30. The simplest way is to
connect the inductor across the RF output
connector J3 and select Inductance from the