MFJ MFJ-1625 User Manual

MFJ-1625 Instruction Manual Window/Balcony Mount Antenna

MFJ-1625 Window/Balcony Mount Antenna

Introduction

The MFJ-1625 Window/Balcony Mount Antenna was designed to provide portable or permanent HF
communications on 80 through 10 meters and VHF on 6 meters. The universal mount design allows the
user to install the antenna in many ways. The mount will easily attach to window frames, balconies, and
railings. The MFJ-1625 works well indoors mounted to a desk or table as well.

The antenna consists of a whip tuner designed for tuning short whips as well as virtua lly any random
length wire antenna, collapsible whip, universal mount, and counterpoise wire. The operating frequency
is found by turning the knobs on the whip tuner and setting them for maximum RF current. The
counterpoise wire length can also be adjusted for maximum RF current. The MFJ-1625
Window/Balcony Mount Antenna will allow the operator to get on the air from locations where antenna
size is limited.

The whip tuner section uses a reversible "L" network. The advantage of the “L” network is that it has
only two tuning controls, and only one tuning solution for given impedance match. The MFJ-1625 has
rear panel connectors for coaxial input and a “Hi-Z/Lo-Z” switch for reversing the “L” network. An
internal input-isolating current balun provides isolation of DC and RF grounds for optimum tuning of the
RF counterpoise.

An RF Current Meter indicates the summed antenna and counterpoise antenna currents, making tuning
particularly easy. Simply tune for maximum RF current.

MFJ-1625 Supplied Components (80-10 meter operation)

• MFJ-1956 12 ft. telescopic whip antenna

• Counterpoise assembly (6, 14, and 26 ft. long wires)

• MFJ-63 Loading Coil Assembly for 40-80 meter operation with the MFJ-1956 12 ft.

telescopic whip antenna

Choosing a Mounting Position
WARNING: ALWAYS ATTACH THE SAFETY ROPE TO A STABLE SUPPORT

BEFORE ATTEMPTING TO ATTACH THE UNIVERSAL MOUNT TO A
WINDOW FRAME OR RAIL. INJURY AND DAMAGE COULD OCCUR
IF THE ANTENNA WERE TO FALL.

1. Locate the MFJ-1625 in a convenient location. The best performance will be obtained by
placing the antenna outside, however the antenna may be used indoors if necessary. Avoid
placing the tuner near microphones, speech processors, computers, TNC's or other RF
sensitive devices.

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MFJ-1625 Instruction Manual Window/Balcony Mount Antenna

2. The design of the antenna allows it to be installed in many ways. It can be easily attached to a
window frame, window box or balcony railing. A Wooden fence is another common mounting
location. The counterpoise is simply placed on the floor. Some installations may require the use
of a C-clamp or vice-grips to secure the base plate.

WARNING: High RF voltages exist at the antenna and counterpoise terminals. Avoid

touching these terminals while transmitting!

Important: Always remember to keep the antenna away from metal objects and out of
reach to prevent injury.

WARNING: SERIOUS RF BURNS AND INJURY CAN OCCUR IF CONTACT IS MADE

WITH THE ANTENNA.

Installation
IMPORTANT: WHILE INSTALLING THE ANTENNA TO A WINDOW OR BALCONY

CONNECT THE SAFETY ROPE OF THE BASE PLATE TO A
SUPPORT.

1. Choose a location to mount the antenna.

WARNING: NEVER MOUNT THE ANTENNA IN A LOCATION CLOSE TO POWER

LINES. SERIOUS INJURY OR DEATH MAY OCCUR.

2. Connect the safety rope to a good support.

3. Attach the mounting bracket in position by placing the bracket over or around the surface of the
support.

NOTE: THE ANTENNA SHOULD BE ORIENTED AWAY FROM WINDOWS AND OTHER

OBJECTS THAT ARE WITHIN CLOSE RANGE IF POSSIBLE.

4. Tighten the screws on the rear of the base plate against the surface of the support. The screws
should be tightened in equal increments to keep the force on the spacer plate proportioned.

5. Loosen the Counterpoise Attachment.

6. Insert the end of the counterpoise wire

7. Tighten to secure the counterpoise.

8. Connect your transceiver’s output to the SO-239 (UHF female) connector labeled
TRANSMITTER on the back of the tuner.

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MFJ-1625 Instruction Manual Window/Balcony Mount Antenna

9. Decide which mount hole will be used on the mounting bracket according to your situation.
There are five holes available.

10. Connect the MFJ-63 Loading Coil Assembly and the MFJ-1956 12 ft. telescopic whip antenna
to the 3/8x24 stud on the top of the mounting bracket and extend to its full length.

Using the MFJ-1625

CAUTION: Never Change The Antenna or Inductor Selector Switch Position While

Transmitting! Never Apply More Than 200 Watts To The MFJ-1625.

Preset the controls on the MFJ-1625 as follows:

• ANTENNA to maximum inductance - Position "A".

• MATCHING to minimum capacitance – Position “10”

• NORM/+C switch to NORM

• COUNTERPOISE to minimum inductance – Position “L”

• Hi -Z/Lo-Z switch (back of unit) to Lo-Z.

• SENSITIVITY control fully clockwise (maximum sensitivity)

Most modern solid state transceivers do not require tuning and loading adjustments. If the transceiver
has a built in antenna tuner, be sure it is turned off or disabled. If your transmitter has an adjustable
output circuit, it must be properly tuned to a 50 ohm load at the operating frequency before adjusting
the tuner. This should be done with a dummy load.

Tuning Procedure

WARNING: Never transmit while changing the INDUCTOR SELECTOR.

1) First, tune for maximum receiver noise as follows:

• While listening to your desired receive frequency, adjust the ANTENNA control for

maximum receiver noise.

• Adjust the MATCHING control for maximum receiver noise.

• Adjust the COUNTERPOISE control for maximum receiver noise.

Note: If no noise peak is evident, try adding extra capacitance with the NORM/+C
switch. Then reverse the HI-Z/LO-Z switch and re-try with both positions of the
NORM/+C switch.

2) Apply just enough power on CW (or AM/FM/RTTY) to obtain a noticeable deflection on the RF
CURRENT meter.

3) Carefully adjust the ANTENNA, MATCHING and COUNTERPOISE controls for maximum RF
current as follows.

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