Section 4: Applications; Tuning Simple Antennas - AEA CIA-HF Operating Manual

The following examples by no means describe the extent of the Analyzer's capabilities, but are
intended as jumping off points. To follow along with the examples, first activate the Analyzer's
expert mode (refer to Function Keys section).

TUNING SIMPLE ANTENNAS

Example: Tuning an 80-meter inverted "V" antenna to 3800 kHz.
Process:
1. Insert the feedline of the 80-meter inverted "V" antenna into the Analyzer's antenna
connector.
2. Turn the Analyzer on. When the S screen appears, press 3 8 0 0 ENTER to change the
default center frequency value to 3800 kHz. Maintain the default width value.
3. A "V" or "U"-shaped SWR curve will appear.
4. Using the F4 (zoom factor) softkey, select the lowest scale values that maintain the bottom of
the SWR curve below the scale's midpoint. (You may have to experiment a little to determine
which scale values work.)
5. Determine on which side of the center frequency the bottom of the SWR curve rests. The
bottom of the curve should indicate the antenna's resonant frequency.
6. To confirm the value of the resonant frequency, press F3 to scroll through the data blocks
until "MIN SWR:xxx at F:xxx" is displayed. This data block indicates the location of the
minimum SWR.
7. Press F5 to enter the Z screen. A "V" or "U"-shaped curve will appear, indicating the absolute
value of Impedance versus frequency.
8. Press F5 again to enter the X screen. The Reactance plot will dip down toward 0 ohms (on
the ve rtical scale) at the resonant frequency.
If the resonant frequency is higher than the center frequency in the SWR plot, you can assume
the Reactance is Capacitive. To tune the antenna to resonance, you either need to add equal
lengths of wire to each side of the "V" antenna, or add an inductor, in series with the center
conductor of the antenna's feedline, at the feedpoint. Press F3 until the Data Box displays the
"L:xxx C:xxx" data block. The C:" value indicates the antenna's equivalent series Capacitance at
the center frequency. The L:" value indicates the series Inductance (conjugate value) needed to
resonate the antenna at the center frequency. You will likely have to experiment with the
Inductance value to find an exact match. Depending on both the Impedance mismatch at the
antenna feedpoint and the length of the feedline, you can use either an inductor or capacitor, in
series with the center conductor of the feedline, to tune for resonance.
If the resonant frequency is below the center frequency, you can assume that the Reactance is
Inductive (i.e. the antenna is TOO LONG). In this case, perform the reverse of the operation
described in the above paragraph.
SECTION 4.
APPLICATIONS
10