MFJ | 1779C | manual | MFJ 1779C - 20-6M DIPOLE, SINGLE BAND, 35 FT Manual

MFJ 1779C - 20-6M DIPOLE, SINGLE BAND, 35 FT Manual
MFJ-1779C 20-6 Meter Dipole Antenna
INTRODUCTION
The MFJ-1779C one-half wavelength, single-band, dipole is a center-fed
antenna that can be tuned for operation on any frequency between 6 meters and
20 meters. (54-14 MHz) The antenna will handle full legal limit power. The
dipole is made using #14 copper wire, a durable center insulator enclosing an
SO-239 connector, and terminated with ceramic insulators. The ends of the
dipole are adjustable and should be cut to the desired length of operation. A
suitable length of wire comes with each antenna to achieve resonance at the low
end of each band.
WARNING: Never place the antenna in a location where contact
with power lines is possible. Death, serious injury, and
damage can occur.
CHOOSING A LOCATION
Choose a location clear from obstructions such as other antennas, buildings, and
power lines. Never place the antenna near power lines. Try to keep the
antenna away from metal buildings and other such structures, which will affect
the performance of the antenna. The optimum height of the antenna is 1/2
wavelength of the operating frequency above ground. This can be calculated by
dividing 468/ (frequency in MHz). Optimum antenna height will vary due to
different ground conditions and nearby objects.
The MFJ-1779C can be suspended from many different supports. The most
common being two trees. The antenna should be suspended using a weather
resistant, non-metallic, nylon rope. Always leave a few extra inches in the
support rope to allow for wind movement of the antenna. This is especially
important when trees are used for supports. If the rope is to tight the antenna
could be damaged.
The antenna can be installed in three different ways:
HORIZONTAL ANTENNA
This installation requires two supports with a minimum distance of the overall
length of the antenna. It is a good idea to also provide a support for the center
insulator of the antenna, which will relieve the stress on the center insulator.
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MFJ-1779C ½ Wavelength Dipole Antenna
Instruction Manual
INVERTED ANTENNA
This installation only requires one tall and two short supports. The center
insulator of the antenna should be the highest point of the antenna.
SLOPED ANTENNA
This installation requires one tall and one short support.
TOOLS AND ACCESSORIES NEEDED FOR ASSEMBLY
•
•
•
•
SWR Analyzer (MFJ-259) OR SWR Meter And HF Radio
Weather Resistant Non-Metallic Nylon Rope
Wire Cutters (large enough to cut #14 wire)
Coax
FREQUENCY ADJUSTMENT
The MFJ-1779C dipole antenna can be tuned for use on any amateur band from
14.0 to 54 MHz. Refer to the tuning chart below for approximate lengths.
ALWAYS HANG THE ANTENNA IN THE DESIRED OPERATING
LOCATION FOR TUNING. CHECK THE RESONANCE POINT OF THE
ANTENNA BEFORE ANY WIRE IS REMOVED.
1. Remove the antenna and parts from the packaging.
2. Decide on the center frequency of operation. The table below has
approximate lengths for each band. Column A gives the approximate lengths
of the entire antenna. Column B gives the length of each side of the dipole.
The lengths can also be determined by using the following formula. This
formula will give the length of the ½ wavelength dipole. This must be
divided by two in order to get the length of each side of the dipole.
468/frequency (MHz)=1/2 wavelength
Band
20
17
15
12
10
6
A
424"(36ft)
312"(26 ft)
267"(23ft)
230"(20 ft)
198" (17ft)
112”(10ft)
2
B
211"(18ft)
156 (13ft)
133" (12ft)
115" (10ft)
99" (9ft)
56”(5ft)
MFJ-1779C ½ Wavelength Dipole Antenna
Instruction Manual
3. Attach a coax to the antenna and place it in the desired location. Be sure to
leave enough rope so the antenna can be lowered for adjustment. Raise the
antenna into is normal operating position using a strong nylon rope. Check
the resonance point. If the resonance point is below the desired frequency the
antenna will need to be shortened.
4. Adjust the antenna according to your calculations or the chart above. Equal
lengths should be removed from each side of the antenna.
5. Install the insulators on each end of the antenna temporarily by placing the
wire through one end hole of the insulator and winding it back around the
dipole wire. Extra wire can be wrapped back around the dipole temporarily
while testing. Always check the resonance point each time wire is removed.
6. When the desired frequency is reached make 5-7 wraps of the wire on the
ends of the dipole for permanent installation. Then raise the antenna until the
desired height is reached and secure it in place by connecting the nylon rope
to a stable support.
TECHNICAL ASSISTANCE
If you have any problem with this unit first check the appropriate section of this
manual. If the manual does not reference your problem or your problem is not
solved by reading the manual you may call MFJ Technical Service at 662-3230549 or the MFJ Factory at 662-323-5869. You will be best helped if you have
your unit, manual and all information on your station handy so you can answer
any questions the technicians may ask.
You can also send questions by mail to MFJ Enterprises, Inc., 300 Industrial
Park Road, Starkville, MS 39759; by Facsimile to 662-323-6551; or by email to
techinfo@mfjenterprises.com. Send a complete description of your problem, an
explanation of exactly how you are using your unit, and a complete description
of your station.
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