Dipole Construction - Yaesu FRG-100 Operating Manual

Performance on a specific band can be achieved
using a simple resonant dipole antenna, consisting
of two equal-length wires cut for the center of the
desired band. The dipole can be constn~cted from
available materials, or from a kit available through
your dealer. If you wish to make such a a dipole for
optimum performance at a certain frequency, the
following formulas can be used to obtain the cor-
rect overall length (add a little extra to allow for
attaching at the ends).
Length (meters)
=
142.5/frequency (MHz), or
Important!
For proper reception, ensure that the LO-Z -
HI-Z antenna selector switch on the rear panel
of the receiver is in the correct position for the
antenna being used. To switch antennas, en-
sure the receiver is turned off and the power is
disconnected, then gently slide the switch
lever using the tip of a pointed object (such as
a ball-point pen).
Length (feet)
=
468/frequency (MHz)
The above HF antennas can be used with vary-
ing success on frequencies outside of their opti-
mum range, in which case an antenna tuner as
mentioned earlier can provide considerable im-
provement in performance. Also, good low fre-
quency reception can sometimes be achieved with
an HF antenna if the two feedline conductors are
connected together to the white HI-Z terminal on
the receiver, but this can also introduce overload-
ing or objectionable noise.
"Length"
The two legs of the dipole must be insulated
from their supports at each end, and from one
another in the center. Reception of long distance
(DX) stations requires that horizontal antennas be
as high above grorlnd
m
possible (with a height of a
little over twice the length of the antenna calcu-
la ted above considered about optimum). Connec-
tion should be made using 50 or 75 Ohm coaxial
cable, with the center conductor connected to one
end and the shield to the other. The other end of the
cable connects to the LO-Z coaxial jack on the rear
panel of the receiver. If the antenna is installed
vertically, it need not be so high (the optimum
center feed point is about the same as the length of
the above formulas), but in this (vertical) case the
earth ground is more critical.
U
Danger!
Do not install any antenna
nem
electric power
lines,
zu?lere
tlzere could be any chance of tlze an-
tenrrn corning into contact with live wires.
HI-Z ANT LO-Z
-
1 0 1
I I
Rear Panel Antenna Selection
Dipole Construction
Insulator
OUPLING
RING
SOLDER HOLE
Installing PL-259 Connector
Insulator
COAX Cable
page
10
.
. v