CHA 40/20 FD
Page 8
Figure 2. Typical BALUN Suspension Method.
16.
Drive a Tent Stake into the ground around 14 feet
past the end of the Antenna Wire. Attach the
Paracord at the end of the Antenna Wire to the
Tent Stake using a round turn and two half-
hitches or similar knot.
17.
Pull the other 7 MHz Antenna Wire until it is fully
extended in the opposite direction from the first
7 MHz Antenna Wire.
18.
Drive a Tent Stake into the ground around three
feet past the end of the Antenna Wire. Attach
the Paracord from the end of the Antenna Wire
to the Tent Stake using a round turn and two half-
hitches or similar knot.
19.
Pull the other 14 MHz Antenna Wire until it is
fully extended in the opposite direction from the
first 14 MHz Antenna Wire.
20.
Drive a Tent Stake into the ground around 14 feet
past the end of the Antenna Wire. Attach the
Paracord at the end of the Antenna Wire to the
Tent Stake using a round turn and two half-
hitches or similar knot.
The four legs of the Fan Dipole will form an “
X
”, which
minimizes interactions between the antenna legs.
21.
Connect the Coaxial Cable to the Radio Set.
22.
Perform Field Tuning Procedure.
Field Tuning Procedure
The Chameleon Antenna
TM
40 / 20 Meter Fan Dipole antenna was designed to be able to be used over a wide
frequency range and installed in variety of ways in the field
–
all of which affect the resonant frequency of the
antenna. Use this simple field tuning procedure to quickly and easily adjust the resonant frequency for each dipole.
Start with the 40m dipole and then do the 20m dipole.
1.
Measure and notate the Standing Wave Ratio (SWR) of the dipole at the lowest, middle, and highest
frequencies in the band or sub-band on which you intend to transmit. One of three following situations will
occur.
Note: When the SWR is 2.0 or less on all three measurements, it is satisfactory, and you can stop the
tuning procedure.
1
st
CASE:
The values for SWR increase on all measurements of the lowest, middle, and highest frequencies,
see figure (3). In this case, the resonant frequency is too low, which means the antenna is too long. This is
the mostly likely case when the Antenna Wires are fully extended. To reduce the length of the dipole, roll
up wire from the end of each Antenna Wire (e) onto the attached Line Winder (i). A rule-of-thumb is that
each half turn made on the Line Winder will increase the resonant frequency of the 40m dipole by around
50 KHz and the 20m dipole by around 200 KHz, giving you a coarse method of resonant frequency
adjustment.
In this example, the antenna is resonant below 7,000 KHz, so if you wanted the antenna to resonate at
7,150 KHZ, you can say that the antenna is resonating at least 200 KHz too low. Using our rule-of-thumb
from above, you would make four half-turns on the Line Winder.
