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MFJ-1778M G5RV JR.
40m through 10m Antenna
INTRODUCTION
The MFJ-1778M antenna is a multi-band center-fed dipole antenna capable of
1500 Watts. The MFJ-1778M consists of 52 feet flat-top fed with 17 feet of 450
ohm matching section ending in an SO-239 coaxial connector.
This antenna generally requires the use of a suitable matching network (antenna
tuner) since the SWR of the G5RV JR is almost certainly not 1:1 on any band.
The use of a tuner will guarantee maximum performance from solid-state
exciters.
The MFJ-1778M is a balanced antenna that is fed by an unbalanced coaxial line.
This feed system causes unwanted parallel RF currents to appear on the shield of
the coaxial feedline. A choke type balun such as the MFJ-915 should be used
with this antenna to eliminate or reduce the undesirable parallel feed line
currents. Failure to use a choke balun may result in RFI, RF feedback, or other
symptoms of RF "in the shack". The Balun Requirement section describes how
to construct a choke balun for this antenna.
WARNING: Always mount this antenna so that it is out of the reach
of adults and children. Contact with any part of this
antenna can cause RF burns or other injuries.
TOOLS AND TIME REQUIREMENTS
This antenna requires no assembly. The time needed for installation will vary
with your skill and equipment.
No special tools are required to install this antenna. Nylon ropes are needed to
support the ends of the antenna from a suitable structure or tree. If a tree is
used, you will need a way to get ropes over it. The most common method is to
use a weighted arrow or a fishing rod and a heavy sinker to place a small line
over a tree. A larger line is then pulled up and used to pull the support rope over
the tree. The ARRL Antenna Handbook has detailed suggestions for installing
wire antennas.
