MFJ MFJ-956 - User Manual

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MFJ-956

Shortwave

Longwave

Antenna

Tuner

Your

MFJ-956

tuner

actually

tunable

preselector

designed

enhance

reception

over

the

continuous

150

KHz

MHz

spectrum.

INSTALLATION

Connect

the

antenna

the

antenna

SO-239

connector

the

tuner.

Connect

the

receiver

the

receiver

SO-239

connector

the

tuner.

OPERATION

sure

the

band

control

properly

set

frequency

band.

Set

the

band

switch

BYP

position.

Tune

your

receiver

the

normal

manner,

listening

for

desired

signal.

Then,

switch

your

tuner

band

control

the

appropriate

frequency

band

and

adjust

the

TUNE

control

for

best

reception.

not

uncommon

for

the

user

notice

very

little

difference

with

without

the

tuner

some

frequencies

when

receiving

conditions

are

optimum.

This

normal.

Usually,

the

greatest

improvement

will

noted

the

lower

frequencies

and

when

images

and

intermodulation

are

bothering

shortwave

reception.

Note:

The

frequencies

indicated

the

RANGE

dial

are

approximate

and

used

for

initial

tuning.

may

necessary

switch

position

higher

lower

frequency

range

for

band-edge

signals

CAUTION:

The

tuner

designed

for

receiving

purposes

only

and

should

not

used

with

transmitting

equipment.

with

all

outside

antennas,

sure

the

tuner

disconnected

from

your

antenna

when

not

use

avoid

lighting

damage.

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This document describes the MFJ-956 Shortwave / Longwave Antenna Tuner, a tunable preselector designed to enhance radio reception.

Function Description

The MFJ-956 is primarily a tunable preselector, not a traditional antenna tuner for impedance matching. Its main function is to improve reception over a broad frequency spectrum by allowing the user to select specific frequency bands and fine-tune for optimal signal reception. It is specifically designed for receiving purposes and should not be used with transmitting equipment. The device aims to mitigate issues like images and intermodulation, which can degrade shortwave reception, especially on lower frequencies.

Important Technical Specifications

Frequency Coverage: The tuner operates over a continuous spectrum from 150 KHz to 30 MHz. This wide range covers both longwave and shortwave bands.
Connectors: It features two SO-239 connectors: one for the antenna and one for the receiver.
Internal Components (from schematic):
- Inductors: The device incorporates a switched bank of inductors, including 2.5 mH, 330 uH, 22 uH, and 1 uH. These inductors are likely selected via the "BAND" control to cover different frequency ranges.
- Variable Capacitor: A 365 pF variable capacitor is used for fine-tuning, controlled by the "TUNE" knob.
- Bypass Switch: A bypass function allows the user to switch the tuner out of the circuit, connecting the antenna directly to the receiver.
Power: The manual does not specify external power requirements, suggesting it is a passive device.

Usage Features

Installation:
1. Connect the external antenna to the SO-239 connector labeled "ANTENNA" on the tuner.
2. Connect the receiver to the SO-239 connector labeled "RECEIVER" on the tuner.
Operation:
1. Initially, ensure the "BAND" control is set to the "BYP" (Bypass) position.
2. Tune the receiver to the desired signal in the normal manner.
3. Once a signal is found, switch the tuner's "BAND" control to the appropriate frequency band that corresponds to the receiver's frequency.
4. Adjust the "TUNE" control on the tuner for the best possible reception.
Reception Improvement: The greatest improvement in reception is typically observed on lower frequencies and when issues like images and intermodulation are present, which often bother shortwave reception. In optimal receiving conditions, the user might notice little difference with or without the tuner.
Range Dial: The frequencies indicated on the "RANGE" dial are approximate and serve as an initial guide. For signals near the edges of a band, it may be necessary to switch the "BAND" control to a position slightly higher or lower than the indicated range for optimal tuning.
Safety Precaution: The tuner is strictly for receiving purposes. It must not be used with transmitting equipment. As with all outdoor antennas, the tuner should be disconnected from the antenna when not in use to prevent damage from lightning strikes.

Maintenance Features

Troubleshooting: If problems arise, users are advised to first consult the relevant sections of this manual.
Technical Support: If the manual does not resolve the issue, MFJ Technical Service can be contacted by phone at 662-323-0549 or the MFJ Factory at 662-323-5869. When contacting support, it is recommended to have the unit, manual, and all station information readily available to answer technician questions.
Contact Information: Questions can also be sent via mail to MFJ Enterprises, Inc., 300 Industrial Park Road, Starkville, MS 39759; by FAX to 662-323-6551; or by email to techinfo@mfjenterprises.com. When sending inquiries, a complete description of the problem, an explanation of how the unit is being used, and a full description of the station are requested.
Lightning Protection: To avoid lightning damage, the tuner should be disconnected from the antenna when not in use.