MFJ MFJ-1775 User Manual

MFJ-1775 Rotatable Mini-Dipole Instruction Manual

MFJ-1775 PARTS LIST

As you unpack your antenna you should find the parts in the following list.

Part Description QTY MFJ Part No.

Balun 1
6-32 x 3/8” screw 80 656-0375S
¼-20 x 1-3/4 bolt 2 662-1760S-HH
6-32 kep nut 80 705-0632S
10-32 hex nut 10 705-1032S
¼-20 hex nut 4 705-2520S
#10 lock washer 5 711-1037S-EX
¼ split lock washer 2 711-2537S-SL
Hose clamp (#16) 8 745-3116S
16” Threaded Rod (2M stub) 2 758-8252
55” Threaded Rod (6M stub) 2 758-8253
640 U-bolt Set 2 758-9200
1/8” Plastic Spoke Caps 35 765-1002
Aluminum “L” Stabilizer Bracket 4 805-1796-7
Fiberglass Stabilizer Insulator 4 807-1796-6
Aluminum Stub Channel Bracket 4 808-1796-5
1 x 12” Fiberglass Rod 1
1-1/8 x 60” AL Tube 2 810-1796-2
30” LONG Spokes 4 810-1796-3C
26” MEDIUM Spokes 8 810-1796-5C
12” SHORT Spokes 24 810-1796-6C
Loading Coil Assembly 2 811-1796-1C1

For installation, you will need some items not supplied with the antenna installation kit:

• A 6'-8' rigid mast or other mounting pipe between 1" and 1.5" outside diameter. (suitable materials
include TV mast sections, galvanized iron pipe, or heavy duty rigid conduit.)

• Quality low-loss 50-Ohm coax with a PL-259 from antenna to transmitter.

An Antenna Analyzer (MFJ-259B or similar), or SWR meter and transceiver

80-1775-10

808-1775-12

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MFJ-1775 Rotatable Mini-Dipole Instruction Manual

MFJ-1775 6-Band Rotatable Mini-Dipole

Introduction

The MFJ-1775 is a mini 14-foot rotatable dipole that is almost invisible from across the street. With its
tiny 7-foot turning radius, it fits on the smallest roof and is perfect for town houses, apartments and
condos. If necessary, it can even be mounted inside an attic!

The MFJ-1775 is inconspicuous and low profile -- not much bigger than a TV antenna, and can easily be
turned by a lightweight TV rotator such as the Hy-Gain AR-35.

And this antenna is no wimp! Its bi-directional pattern can help reduce QRM/noise while maximizing
your signal in the directions that you want -- so you can work some real DX. You can operate 6 bands -­40, 20, 15, 10, 6 and 2 meters -- and run up to a full 1500 Watts SSB on all HF bands.

The MFJ-1775 features automatic band switching, and uses highly efficient end-loading with its entire
length always radiating. With 6 and 2 Meters thrown-in, you have ham radio’s most versatile rotatable
dipole!

TM

Each HF band uses separate, efficient end-loading coils wound on fiberglass forms with Teflon
and capacitance hats (no lossy traps). 6 and 2 meters are full-length half-wave dipoles.

wire,

The MFJ-1775 is built-to-last – using an incredibly strong, solid fiberglass rod center insulator and 6063
T-6 aircraft strength aluminum tubing for the radiator. And it assembles in an afternoon.

WARNING: Improper installation and assembly can be hazardous! Read these instructions
thoroughly before attempting to assemble, install or operate this product! High power transmitting
devices produce voltages that can cause severe burns or other injuries.

SPECIFICATIONS

The small size of the MFJ-1775 is accomplished by adding separate loading coils and capacitance hats at
each end of the antenna for the HF bands. The efficient end-loading coils are wound on fiberglass forms.
The six and two meter amateur bands are covered with the addition of four quarter-wave decoupling
stubs.

Electrical Specifications

Power
Band CW SSB 2:1 SWR BW
40m 1500 1500 40 KHZ
20m 1500 1500 60 KHZ
15m 1500 1500 400 KHZ
10m 1500 1500 1.2 MHZ
6m 300 750 600 KHZ
2m 200 300 4.0 MHZ

Mechanical Specifications

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MFJ-1775 Rotatable Mini-Dipole Instruction Manual

Mast Size: 1- to 1-1/2” diameter
Overall Length: 14 feet
Turning Radius: 7 feet
Weight: 15 pounds
Wind Load: 2 square feet

CHOOSING A LOCATION FOR THE ANTENNA

For best performance on receiving and transmitting, mount the antenna in a clear location above or away
from buildings, towers, feedlines, utility wires, and other antennas. While your own ingenuity and
particular circumstances will determine the final mounting method, we'll pass along a few ideas for both
permanent installation and portable operation.

• Never mount this antenna in a location that will permit unsuspecting people to come in contact with

the loading spokes or any other part of the antenna.

• Never mount this antenna where a mechanical failure might allow the antenna to contact power lines

or other utility wires.

• Always ground the feedline at the point where it enters a building to a good earth ground for

lightning protection.

WARNING: Always mount this antenna so that it is out of the reach of adults and children.
The capacitance elements can cause injury and/or severe RF burns.

Permanent Installation

The ideal installation is a rigid pole or roof mount that puts the antenna completely in the clear. If the
ideal installation is not possible, choose the best compromise. TV mast, heavy-duty rigid electrical
conduit, and steel water pipes are suitable mast materials. This antenna will mount on masts between 1
and 1-1/2" OD. The use of soft or thin wall masts is not recommended

Portable Operation

The MFJ-1775 may be disassembled as necessary for transporting to a temporary location. Ideally, just
remove the two HF loading coil assemblies leaving the two main elements and 2- & 6-meter stub
assemblies intact. Some retuning may be required after moving the antenna.

Even for temporary or portable operation, do not be casual about selecting a suitable mast. If the antenna
falls, it will be damaged and may cause serious injury. Whatever type of installation you choose,
remember that the antenna should be installed where it can never be contacted by people or animals or
come in contact with power lines.

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MFJ-1775 Rotatable Mini-Dipole Instruction Manual

TOOLS AND TIME REQUIRED FOR ASSEMBLY

The estimated assembly time is two hours. Antenna assembly requires the following hand tools:

• #2 Phillips screwdriver

• 5/16" nut driver for #6 nuts and hose clamps.

• Small (4”-6”) adjustable wrench OR

o 3/8" wrench for 6 and 2 meter stub nuts
o Two 7/16" open-end wrenches (or wrench and nut driver) for U-bolts and

center insulator bolts.

• Heavy wire cutters for trimming capacitance spokes

• Pliers for holding the spoke ends as they are trimmed

• Safety glasses.

You also need two stable supports at least 30" tall (saw horses, trash cans, etc) during assembly, and a
short (6-8') temporary mast (1 to 1-1/2" OD) for temporary mounting during tuning.

SAFETY PRECAUTIONS:

WARNING! You can be killed if the antenna, feedline, or the equipment used to install the
antenna accidentally contacts any utility lines. Never install an antenna near power lines!

1. Be careful while climbing and carrying the antenna. It is heavy enough to cause you to lose your

balance if it is handled too casually or if the capacitance spokes are snagged on a gutter, ladder, tree
limbs, etc.

2. Mount the antenna high enough so that it is out of reach. The ends of the capacitance spokes can

cause eye injury, serious RF burns or both.

3. Make sure that the mast is sturdy enough to support the 15 pound weight and the wind loading of

approximately 2 square feet.

ASSEMBLY and INSTALLATION PROCEDURE

Refer to the figures in this manual during assembly. Assembly consists of putting together the
balun/center insulator assembly, then connecting the aluminum radiating elements to the balun/center
insulator assembly. Next the 6- and 2-meter stub elements are installed. Finally the loading coil
assemblies are assembled and installed on the aluminum radiating elements.

The 6- and 2-meter stubs are not required if you have no interest in operating on these bands. HF band
operation will not be affected if the 6- and 2-meter stubs are not present.

After the antenna is assembled and adjusted for resonant frequency and SWR, it can then be mounted on a
tower or rooftop and given final adjustments.

WARNING: Wear safety glasses whenever working with this antenna.

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