MFJ MFJ-1778M G5RV JR. User Manual

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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.

MFJ MFJ-1778M G5RV JR. Specifications

General

Impedance	50 ohms
Max Power	1500 watts
Connector	SO-239
Weight	2 lbs
Configuration	Dipole

Summary

Introduction and Initial Setup

Introduction to MFJ-1778M G5RV JR. Antenna

Overview of the MFJ-1778M antenna, its capabilities, and components like flat-top, matching section, and connector.

Antenna Mounting Safety Warning

Warning to mount the antenna out of reach of adults and children to prevent RF burns or other injuries.

Tools and Time Requirements for Installation

Details on assembly, time, and tools needed for installation, including nylon ropes and methods for getting them over trees.

Safety and Installation Procedures

General Safety Precautions

Essential safety warnings regarding electrical conductors, power lines, RF burns, and keeping the antenna away from children and animals.

Antenna Installation Guidelines

Suggestions for optimal antenna location and three basic installation methods: Horizontal, Inverted 'V', and Sloper.

Balun and Antenna Configuration

Sloper Antenna Installation

Details on using the antenna as a sloping dipole with one tall and one short support, radiation direction, and optimum angle.

Balun Requirement and Selection

Explanation of the need for a 1:1 choke balun to prevent parallel RF currents and RFI, recommending air-core baluns over ferrite types.

Air-Wound Balun Construction

Instructions for constructing an air-wound balun by winding the coaxial feed line, specifying turns, diameter, and placement.

Tuning and Grounding

Balun Proximity Warning

Warning to keep the balun away from any conductive material to prevent issues.

Antenna Tuning Requirements

Explanation that a tuner is required for matching transmitter impedance and recommendations for tuning adjustments.

Grounding Considerations for Safety and Protection

Importance of good earth ground for lightning protection and safety, detailing methods like burying feedlines and using ground rods.

Maintenance and Support

Antenna Maintenance and Connector Protection

Recommendations for connector moisture protection using silicone grease or coax seal to prevent corrosion.

Technical Assistance and Support

Information on obtaining technical help from MFJ Enterprises via phone, mail, facsimile, or email, including required problem details.