MFJ MFJ-662 User Manual

Table of Contents

Introduction..........................................................................................................1

How Your MFJ-662 Simplex Repeater Works.....................................................1

Jacks and Controls................................................................................................2

Specifications.......................................................................................................2

Power Sources......................................................................................................3

Interface Connections...........................................................................................4

Set-up Testing and Operation...............................................................................4

Selecting a PTT Interface.....................................................................................6

Record Level........................................................................................................6

Transmit Level.....................................................................................................7

Simplex Repeater Operating Tips.........................................................................7

Repeater Set-Up Suggestions ...............................................................................8

Theory of Operation.............................................................................................9

In Case of Difficulty............................................................................................. 9

Technical Assistance..........................................................................................10

Schematic...........................................................................................................11

MFJ-662 Instruction Manual Simplex Pocket Repeater

INTRODUCTION

Congratulations on purchasing the MFJ-662 Simplex Pocket Repeater. This
small unit houses everything you need to turn your HT, mobile, or base-station
radio into a range-extending simplex repeater system. The MFJ-662 may be
small, but it's loaded with high-tech features:

32-Second Memory: Captures your entire message with time to spare.
PIC Controller: Reliable PIC technology manages each function flawlessly.
Adjustable Gain: Programmable transmit level ensures best audio quality.
Selectable PTT Interface: Keys load-sensing or ground-contact PTT circuits.
Small Size: Ultra-compact pocket-sized case fits anywhere.
Flexible Power: Uses single 9V battery or any external 9-15 Vdc source.
Versatile Interface: Open-ended patch cable adapts to virtually any radio.
Courtesy Tone: Controller signals the end of repeated messages.

HOW YOUR MFJ-662 SIMPLEX REPEATER WORKS

Repeater stations extend communication range beyond line-of-sight by
intercepting and re-transmitting signals from a favorable location. Repeaters
may be either duplex or simplex in design. Most Hams are more familiar with
the sophisticated duplex systems set up by repeater groups to expand mobile
communication. These repeaters occupy two channels, one for listening and one
for simultaneously re-transmitting. Duplexing offers the convenience of real­time conversation, but the hardware is generally too large and complex to move
around for portable use.

Tower

1

Station

Antenna

duplexer

Duplex Repeater Station

Receiver

Control

Controller

Transmitter

Amplifier

Power
Supply

Link

Auto­patch

Simplex Repeater Station

Telco

Line

MFJ-662

Simplex

Controller

Rock

Portable

HT

MFJ-662 Instruction Manual Simplex Pocket Repeater

Unlike duplex systems, simplex repeaters require only a portable transceiver and
a self-powered controller such as your MFJ-662. They occupy a single channel
and use solid-state voice-memory to record and then repeat each incoming
transmission. Simplex repeaters are especially useful for increasing the range of
hand-held HTs and mobile units participating in field activities such as races,
missing-person searches, hunting trips, disaster communication, and special
events. All you need is an accessible elevated location and a minute or two of
time to place your repeater in service.

JACKS AND CONTROLS

3

Rec

RADIO

INTERFACE

1

1. Interface Jack: Accepts 5-pin IDC plug for Mic, Record Audio, PTT lines

and ground.

2. Record Indicator: LED illuminates when controller is recording.

PWR

2

MFJ-662

4

3. Power Off/On: Applies power to controller from internal battery or external

jack.

4. External Power: Accepts 2.1-mm plug (9-15 Vdc source), disconnects

battery.

SPECIFICATIONS

Power Source .......................... 9V battery or 9-15 Vdc supply

Current Drain .......................... 3.5 mA Standby

PTT Mode .............................. Selectable (ground-contact or load-sensing)

Voice Memory ........................ 32 Seconds total storage

Dimensions ............................. 2.3" x 1" x 3.7"

Weight .................................... ≈2 oz.

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MFJ-662 Instruction Manual Simplex Pocket Repeater

POWER SOURCES

1. Internal Power: Use a fresh premium-grade alkaline 9 volt battery. To
install, remove the compartment cover by pressing in and sliding downward with
your thumb (see below). Locate the battery snap-clip inside and connect it to the
battery terminals. Place battery inside and reinstall the lid.

9-Volt
Alkaline
Battery

Important Note:

battery installed. Leakage and corrosion could damage your unit.

Never store your controller for extended periods with the

2. External Supply: Power from any well-filtered 9-15 Vdc source--including

13.8 volt station supplies, 12 volt automotive systems, or external battery packs.
Protect both power leads with ½ Amp fuses when using high-current sources.
The controller's external power jack accepts a 5.5mm x 2.1mm coaxial plug.
You may obtain extra plugs from RadioShack (274-1567 or equivalent). Wire
(+) voltage to center terminal, and (-) to common, as shown below.

-

1/2-A

-

+

Important Note:

etc.) may damage your controller. Never apply more than 20 volts to your
unit.

Unregulated DC sources (simple wall cubes, solar panels,

1/2-A

Power Supply

+

To power from an unregulated source, use a simple regulator circuit such as the
one shown in the following diagram.

3

MFJ-662 Instruction Manual Simplex Pocket Repeater

(

)

(

)

LM7812 Regulator

15 - 28 V

Unregulated

Source

+

.1 uF

-

.1 uF

+

12 V Reg.

-

3. MFJ-1312B: Power your controller directly from AC mains using the MFJ­1312B 9 volt power supply. This comes with a 2.1mm plug pre-installed, and is
available from MFJ Enterprises, Inc. or a MFJ dealer.

INTERFACE CONNECTIONS

A 5 pin IDC jack on the front panel of the MFJ-662 provides access to the
interface lines for your radio. Use the supplied IDC plug and open-ended patch
cord to prepare an interface cable. A front-panel view of the IDC connector's
pin-out is shown below:

Facing Front Panel

PTT Line

(Gnd-Sw Only)

Ground

To Mic

Record Playback

From Spkr

PTT Line: FET switch pulls PTT line to ground in MBL (mobile) mode.
Ground: Common return for PTT, microphone, and speaker line.
Playback: Sends mic-level audio to radio, provides PTT sense-load in HT

mode.
Record: Terminates radio's speaker line, sample s off-air audio for re cording.
See your radio's instruction manual for pin-out connections at the transceiver

end. Many popular connectors, including 8-pin mic plugs and mini-plugs, are
available from Radio Shack, Ham stores, or MFJ. You may also purchase an
interface cable terminated for Kenwood, Yaesu, Alinco, or Radio Shack
transceivers directly from MFJ for $15.95.

SET-UP TESTING AND OPERATION

For initial controller set-up, use a second "test" radio tuned to the desired
operating channel (a HT set for low RF-output is a good choice). This will be
used to check the controller's operating functions and playback level.

4

MFJ-662 Instruction Manual Simplex Pocket Repeater

1. Set Receiver Volume and Squelch: Turn on the repeater radio and set its

Volume control for a low but co mfortable l istening level through the sp eaker
(this step establishes the controller's record level). Set the Squelch to quiet
FM background noise.

2. Connect the Controller: Plug the controller's patch cable into the repeater

radio. The Rec-Aud line goes to the radio's External Speaker jack, and the
Mic-Audio/PTT line(s) go to the radio's Microphone jack. Make sure the
controller is set up for your radio's PTT circuit (see PTT-Interface section on
the next page).

3. Record A Test Transmission: Turn the controller On. Key the test radio,

pause for 1 second, then send a short test transmission by speaking normally
into the microphone.

The controller's Rec LED should illuminate, indicating the controller is detecting
the test signal and capturing your message. Keep the test transmission under the
32 second record time limit. When finished , unkey the test radio and listen for
playback. The controller's Rec LED should go out and the repeater radio should
switch into transmit mode and return your message.

4. Check Playback Level: Speech should sound natural and modulation

should match other off-air signals (3-5 kHz peak deviation). If audio is
"thin" and weak, or if it is "mushy" and distorted, refer to the Transmit Level
section of this manual. You will need to adjust the controller's playback
level.

5. Courtesy Tone: At the end of each message playback, the controller will

insert an audib le " beep" befo re unkeying the transmitter. T his tone ind icates
the repeater has finished repeating the current message and is ready to receive
the next message.

6. Test Mode: The MFJ-662 has a built-in test function to report status

information from its PIC controller (model number, software version, etc).
To activate this function:

(a.) Turn off your controller.
(b.) Open the radio's squelch.
(c.) Turn the controller back on.

The repeater should switch to transmit and send a stored CW message,
simultaneously flashing the Rec LED and keying the courtesy tone oscillator.
This message provides an indication that the PIC is working properly.

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MFJ-662 Instruction Manual Simplex Pocket Repeater

If your repeater performs normally and levels are set properly, then it's ready for
set-up and operation in the field. If it fails to function normally, refer to the set­up section below--and to the In Case of Difficulty section at the end of the of the
manual.

SELECTING A PTT INTERFACE

The MFJ-662 works with transceivers using load-sensing or ground-contact PTT
circuits. Internal jumper JMP1 selects switching mode. JMP1 is normally pre­set at the factory for load-sensing radios. To change modes, remove the
controller's two case screws and gently separate the case halves. On the pc
board, locate JMP1, a 3-pin header.

MBL

JMP1

HT

At JMP1, set the jumper plug for the t ype of PTT keying used b y your radio:
MBL: For mobile or base rad ios using ground-contact PTT switching.
HT: For HTs or o t her radios using load-sensi ng PTT switching.

Note that ground-contact switching uses a separate PTT line, while load-sensing
combines the mic and PTT lines together. If you don't know which type of
activation your radio requires, consult its operating manual for specifics. This
information is often found under RTTY/Packet set-up instructions, or on the
microphone connector pin-out diagram.

RECORD LEVEL

Set up your contr o lle r's o ff-ai r r ec o rd leve l with the transcei ver 's Volume control.
To adjust, set Volume for a low but c o mfort ab le li ste ning l eve l fo r off-a ir signa ls
while listening through the radio's built-in speaker (as described in Operating
Instructions). Each time you use the repeater, remember to return the volume
control to the same approximate setting. This is important because any radical

change in the volume setting will be reflected in the voice-recorder's playback
level. This, in turn, could upset the modulation level of your re-transmitted

signal.

6

MFJ-662 Instruction Manual Simplex Pocket Repeater

IMPORTANT WARNING: NEVER ADJUST TRANSC EIVER VOLUME WITH THE
SPEAKER CUT OFF. THIS COULD RESUL T IN OVER DRIVIN G THE RECORD ER
IC--AND MAY EVEN DAMAGE THE CONTROLLER'S INTERNAL LOAD
RESISTOR.

TRANSMIT LEVEL

Before attempting to set up the controller's transmit level, make certain the
transceiver's Volume control is set correctly (see paragraph above). To adjust
transmit level, use a second test radio to monitor the repeater's on-air signal
quality (see Operating Instructions). For mor e a percise signal evaluation, you
may also use a FM deviation meter or FM service monitor.

The MFJ-662 has four (4) transmit-level settings to accommodate a wide range
of transceiver speech-amplifier circuits. Levels are selected by positioning
jumper-plugs on headers JMP2 and JMP3 (illustrated below). If the repeated
audio is too weak, increase it by moving jumpers for a higher drive level. If
audio level is too strong (mushy or bassy), set the jumpers for a lower audio
output level. Your objective is to obtain the most natural playback quality
possible fo r normal on-air signals (i e. incoming signals with 3-5 kHz peak FM
deviation).

JMP3 JMP2

1

Lowest Output Highest Output

23

Gain Setting

4

5

If there's an unuse d jumper plug, install it o n any free header pin to p revent it
from becoming misplaced.

IMPORTANT WARNING: NEVER ATTEMPT TO INCREASE TRANSMIT LEVEL
BY TURNING UP YOUR TRANSCEIVER'S VOLUME CONTROL WITH THE
SPEAKER CUT OFF.

SIMPLEX REPEATER OPERATING TIPS

Pick-Up Time: After keying the mic, pause a second before speaking (if you
speak immediately, the controller may "clip" a portion of your first word).

7

MFJ-662 Instruction Manual Simplex Pocket Repeater

Drop Time: Wait for the "beep" before transmitting your reply.
Message Capacity: Message capacity is 32 seconds. In practice, simplex

repeater users usually keep transmissions much shorter to minimize wait-time.
Message Overflow: When a incoming transmission overflows the 32-second

memory, the controller automatically replays what's been recorded. This
protocol keeps information moving, and also provides a measure of protection
against an unwanted signal l ocking up the controlle r.

ID-ing: Remember to voice-ID your repeater in compliance with FCC
guidelines. You may do this in the course of normal conversation.

REPEATER SET-UP SUGGESTIONS

Your MFJ-662 may be set up for base, mobile, or portable operation. Here are
some suggestions to help you get the best performance from your simplex
repeater:

MFJ

662

AC

Supply

Base

Station

Station

Antenna

Mobile

MFJ

662

Accessory

Jack

MFJ

HT

662

Portable

Operating Environment: When leaving your repeater at an unattended site,
always protect it from direct exposure to sun, rain, snow, and extreme
temperatures.

Frequency: Whenever possible, avoid using popular simplex frequencies where
your repeater might interfere with out-of-area communication.

Power: Run only as much power as needed for the coverage area. High power
wastes battery time and may draw unwelcome attention from out-of-area
stations.

Location: Position your repeater in an accessible location. In the event of a
malfunction or intentional jamming, you may need to go there and shut it down
quickly.

Security: Always secure the site. Leaving a repeater exposed and unattended in
a highly-public open area invites tampering, vandalism, unauthorized use, or
theft.

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MFJ-662 Instruction Manual Simplex Pocket Repeater

THEORY OF OPERATION

Rec

Out

JMP2/3

Sense

Load

PTT

JMP1

Q1

FET

Sw

Mic

Aud

Out

Gnd-Sw

PTT

U2

Voice
Record­Playback

In

Rec

Audio

In

U1

PIC

Control

U3

Signal

Detector

Load

Speaker level audio is routed from the repeater transceiver's AF-output stage to a
10 ohm resistive load in the controller. An audio sample is passed to signal­detector U3--where it is amplified and used to cue PIC-controller U1 when a
incoming signal is present. When a signal is detected, U1 activates voice­recorder-IC U2's record mode and illuminates the Rec LED. At the same time, a
second un-amplified audio sample is passed to the input line of U2 for recording.

When the incoming signal drops, or when U2's memory overflows, controller U1
turns off the Rec LED and cues U2 to enter playback mode. It also activates Q1-

-providing PTT closure to the transceiver to initiate a transmission (ground­closure or load-sensing PTT selected at JMP1). Playback audio is then routed
from U2 to the tr ansceiver's mic line through transmit-level att enuator JMP2/3.
When message playback is complete, U1 injects a courtesy "beep" onto the mic
line and turns off Q1--dropping the transmitter's PTT circuit. This terminates the
repeater's record/playback cycle and places the controller in standby mode to
await the next message.

IN CASE OF DIFFICULTY

Won't Power Up: Check battery condition or external power supply
connections.

Won't Activate Transmitter: Check PTT wiring, PTT jumper JMP1.
Weak Transmit Audio: Check volume setting, adjust Transmit Level JMP2/3.

9

MFJ-662 Instruction Manual Simplex Pocket Repeater

Distorted Transmit Audio: Check volume setting, adjust Transmit Level
JMP2/3.

Won't Record Off-air: Check record-audio line from external speaker jack.
Records, No Transmit Audio: Check playback-audio line to mic jack.
Other Problems: Run "Test Mode" to see if controller responds.

TECHNICAL ASSISTANCE

If you have any problem with this unit first check the appropriate section of this
manual. If the manual does not reference your problem or your problem is not
solved by reading the manual you may call MFJ Technical Service at 662-323-
0549 or the MFJ Factory at 662-323-5869. You will be best helped if you have
your unit, manual and all information on your statio n handy so you can answer
any questions the technicians may ask.

You can also send questions by mail to MFJ Enterprises, Inc., 300 Industrial
Park Road, Starkville, MS 39759; by Facsimile to 662-323-6551; or by email to
[e-mail]. Send a complete description of your problem, an
explanation of exactly how you are using your unit, and a complete description
of your station.

10

MFJ-662 Instruction Manual Simplex Pocket Repeater

SCHEMATIC

11