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MAGNUM 257
OPERATING MANUAL
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Copyright © 1999 by Magnum International. All rights reserved.
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TABLE OF CONTENTS
Introduction ......................................................................................................... 4
Limited Warranty ................................................................................................. 5
Installation ...................................................................................................... 6 - 7
Front Panel Controls .................................................................................... 8 - 10
Other Features.................................................................................................. 10
Specifications.....................................................................................................11
Contact Information........................................................................................... 12
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INTRODUCTION
Congratulations on your purchase of a Magnum 257 10 meter FM/SSB/AM transceiver. The 257 is designed
to provide years of enjoyment and trouble-free service. There are many features and functions designed into
this transceiver. To ensure that your investment is enjoyed to its fullest extent, please take a few moments
and thoroughly read this manual.
The Magnum 257 is a microprocessor controlled, user programmable radio combining high RF performance
with a user-friendly environment. The 257 is a 12 volt DC, HF transceiver designed for mobile use. The
transceiver utilizes the latest in surface mount production techniques. This keeps the size of the unit to a
minimum without sacrificing any of the advanced circuits required for today’s high performance radios, and
as cabin space diminishes in modern vehicles, this concept helps create a wider variety of installation options. Although engineered with mobile use in mind the 257, with the addition of a high quality 10-amp power
supply, may be easily adapted for fixed station operation.
Some of the features of the 257 are; an advanced design liquid crystal display that provides the operator with
a full visual account of the transceivers operating status, automatic frequency scanning from either the front
panel or microphone, memory storage of your favorite frequencies and modes, programmable frequency
resolution of either 1 kHz, 10 kHz or 100 kHz, and split frequency operation for repeater use. These are just
a few of the features that make the 257 a pleasure to own and operate.
IMPORT ANT
United States or within it’s territories a licensed amateur radio operator must be present at the station. The
minimum license class to operate 10 meter phone is Novice/Technician. If you are studying for your license
and want to familiarize yourself with the operation of the radio, the receiver may be operated with or without
a licensed operator present. For more information regarding FCC licensing, contact your nearest amateur
radio dealer, or for complete details contact the American Radio Relay League.
: The Magnum 257 is designed for amateur radio use. If the transmitter is operated in the
American Radio Relay League (ARRL)
225 Main Street
Newington, CT 06111
Telephone 860-594-0200
Facsimile 860-594-0259
http://www.arrl.org
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LIMITED WARRANTY
Magnum International warrants this product to be free of defects for a period of one (1) year from the original
date of purchase. This warranty is non-transferable. This limited warranty is subject to repair or replacement
of defective components only. This warranty is void if the radio has been tampered with or misused.
IMPORTANT: RETAIN YOUR SALES RECEIPT
The enclosed warranty registration form must be filled out and mailed along with a photocopy of your sales
receipt within 15 days from the purchase date. If the warranty registration form and copy of your sales receipt
are not received the radio is not covered under warranty. Please fill out the enclosed warranty registration
form and send it along with a copy of your sales receipt to:
Magnum International
PO Box 445
Issaquah, WA 98027
Registering your 257 with Magnum provides several benefits:
1) Validates your warranty.
2) Entitles you to free updates and information regarding your radio and new accessories for your radio.
3) Provides possible recovery of lost or stolen radios through our serial number tracking database.
4) Receive your free Magnum logo baseball cap within 30 days after registering.
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INSTALLATION
1. Contents
Unpack and inspect your Magnum 257 for missing or
damaged components. Your 257 includes the following items:
Quantity Description
1 Magnum 257 Transceiver
1 Microphone with Up/Down Controls
1 Mounting Bracket with Hardware
1 Microphone Hanger with Hardware Set
1 Operating Manual with Schematic
Connect the positive (+) red wire of the DC power cord
to a positive 13.8 volt source at the vehicle fuse block.
If connecting to the fuse block, it is recommended that
a switched power source is used so that the power to
the transceiver is disconnected when the vehicle is off.
This will eliminate the possibility of the transceiver draining the vehicle’s battery .
Connect the negative (-) black wire to a metal part of
the vehicle’s frame, or chassis ground. Make sure that
this is a good ground connection.
2. Microphone Hanger
The microphone hanger may be attached to the side
of the transceiver, or any other convenient location. Use
the provided screws to attach the microphone hanger
either vertically or horizontally to the side of the transceiver.
3. Mounting
When attaching the 257 mounting bracket to the vehicle, choose a location that will provide easy access
to all front panel controls and air circulation to the rear
panel. When selecting a mounting location, make sure
that there is ample space behind the control deck for
the cables. Do not pinch, or bend sharply , the power or
antenna cables. Do not install the 257 in any compartment that restricts airflow and do not install in a location that interferes with the safe operation of the vehicle.
Attach the mounting bracket to the vehicle first then
mount the 257 to the bracket. If the rear panel is not
accessible you may want to attach the power and antenna cable prior to mounting.
4. Electrical Connections
The Magnum 257 is designed to work on any 13.8 volt
DC, negative ground, source. The condition of a
vehicle’s electrical system can affect operation. A low
battery , worn generator/alternator, or poor voltage regulator will seriously impair the performance of the transceiver. Any of the above conditions could result in a
high level of receiver noise generation or a substantial
loss of the transmitter’s RF output. Make sure that all
of these components of your vehicle’s electrical system are in good condition prior to installing the transceiver.
CAUTION!
VOL T AGE EXCEEDING 15 VDC WILL DAMAGE
THE RADIO. MEASURE VOL TAGE A T BA TTERY
TERMINALS, WITH VEHICLE RUNNING, PRIOR
TO INST ALLA TION!
Before making any electrical connections make sure
the AF gain (volume) control on the control deck is in
the “OFF” position.
The 257 power cord may also be connected directly to
the battery. Connecting directly to the battery has several benefits, the first of which is to maximize RF output. Secondly , the battery is a very large capacitor and
will help eliminate certain types of ambient and vehicle
noise. If connecting directly to the vehicle’s battery , additional power cable may be required. On runs of 8
feet or less use 14-gauge stranded wire. Use 12-gauge
wire on longer runs.
5. Antenna Connection
The transceiver will operate using any standard 50ohm ground-plane, vertical, mobile whip, long wire or
similar antenna. The antenna should be rated at 50
watts PEP minimum. A standard SO-239 type antenna
connector is located on the rear panel of the 257. Connection is made using a PL-259 and high grade coaxial cable (RG213, RG58A/U or Mini RG-8 is recommended).
A ground-plane antenna provides greater coverage and
is recommended for fixed station-to-mobile operation.
For point-to-point fixed station operation, a directional
beam antenna operates at greater distances even under adverse conditions. A non-directional antenna
should be used in a mobile installation; a vertical whip
is best suited for this purpose. The base loaded whip
antenna normally provides effective communications.
For greater range and more reliable operation, a full
quarter wave whip may be used. Either of these antennas uses the metal vehicle body as a ground plane.
Once the antenna is mounted on the vehicle, route the
coaxial cable so that it is not next to any power cables
or vehicle cables. Connect the PL-259 to the antenna
connector on the rear panel of the 257. Make sure that
the cables does not interfere with the safe operation of
the vehicle.
6. VSWR
Before use, it is important to determine the antenna
system’s VSWR (voltage standing wave ratio). First,
make sure the SWR bridge (meter) is in good working
order and is calibrated. To ensure your radio is performing properly the VSWR should never exceed 1.5
to 1. Never transmit on any antenna system where the
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VSWR exceeds 1.8 to 1. This will stress the output
stage and could destroy the RF transistors; this type of
misuse and failure is not covered under warranty.
Measure the VSWR at the center of the operating band.
Tune the antenna (according to the manufacturer’s
tuning instructions) so that the VSWR is as close to
1.1 to 1 at the center of the operating band.
Next, measure the VSWR at the lowest and highest
frequency of the transceiver. If the antenna has a wide
enough frequency range and band-pass, the VSWR
readings should be below 1.5 to 1 across the entire
operating band. If at the lower or upper end of the transceiver operating frequency, the VSWR measures more
than 1.5 to 1, it is recommended that the antenna be
re-tuned before operating on those frequencies.
If you are experiencing unusual VSWR readings check
for the following possible problems:
1) Make sure that the antenna is installed properly and
grounded.
2) Check all coaxial cable and connectors for defects
and poor routing.
3) If testing a vehicle installation, make sure that all
vehicle doors are closed when testing.
4) Do not test near or around large metal objects or
buildings.
7. Ignition Noise
In certain vehicle installations, electrical noise or interference may be present in the receive audio of the transceiver. Typically the vehicle’s ignition system or more
specifically the alternator generates this noise. The
Magnum 257 is equipped with a noise blanker circuit
that is designed to improve, and in many instances
eliminate, this electrical noise.
In extreme cases, the noise blanker may not eliminate
all the electrical noise. In such cases, an after-market
alternator noise or ignition noise filter can be purchased
and installed according to the manufacturer’s instructions. If purchasing an alternator noise filter for the
Magnum 257 make sure the filter is rated for at least
10 amps continuous current draw.
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16 17 12 13 1514
FRONT PANEL CONTROLS
1. MICROPHONE INPUT
A 6-pin, lock ring type, microphone connector is used.
Microphone wiring is as follows:
Pin 1 : Microphone Audio
Pin 2 : Receive
Pin 3 : Transmit
Pin 4 : Down (Up w/ 22K Ohm Resistor)
Pin 5 : Ground
Pin 6 : +13.8 VDC
2. MICROPHONE GAIN CONTROL
Increases or decreases the energy developed in the
microphone amplifier circuit. The gain increases as the
control is rotated clockwise. For optimum setting, press
the push-to-talk (PTT) switch on the microphone, adjust the mic gain control until all segments of the S/RF
display are lit. Next, rotate the control counterclockwise until the last segment of the display starts to flicker.
The S/RF display is the bar graph located on the lower
edge of the LCD screen.
3. RF GAIN CONTROL
Adjusts the receiver sensitivity to both signals and background noise. This affects the distance at which a signal can be detected. Turning the control counterclockwise reduces the receiver sensitivity. This is particularly useful in areas where large volumes of traffic (signals) are present. The S/RF display indicates the received signal’s strength. The S/RF display is the bar
graph located on the lower edge of the LCD screen.
3
2
5
4 101
4. STEP \ NB \ 1
STEP: Tuning Step. The STEP control selects fre-
quency resolution in either 1 kHz, 10 kHz or 100 kHz
steps. Press the STEP button, one of the digits will
flash on and off. Press the STEP button again to change
stepping resolution.
To tune frequencies in either 10 kHz or 100 kHz increments, press the STEP button until the desired digit is
flashing. Rotate the FREQUENCY control in either direction. The entire frequency range of the Magnum 257
can be stepped through in 10 or 100 kHz increments.
To tune in 1 kHz increments, press the STEP button
until the 1 kHz digit flashes on and off. Rotate the FREQUENCY control. NOTE: When stepping in 1 kHz increments, you are limited to tuning within a 10 kHz
frequency range.
NB: Noise Blanker. Noise blanker on and off control.
This circuit eliminates pulse type interference usually
associated with automotive ignition systems. To activate the noise blanker, press the FUNC control and
then press the NB button. NB will appear on the LCD
indicating the noise blanker is turned on. To turn off
the noise blanker, repeat the same process.
1: Memory Channel 1. After programming this button
is memory channel 1. See M.LOAD \ M.SAVE control
for programming instructions.
7
6
9
8
11
IMPORTANT!
Operating some of the features in 4 through 9 require the use of the function control. To activate
the function control, momentarily push the FUNC
(10) control, the FUNC prompt will be displayed in
upper left-hand corner of LCD. Push the control
again to deactivate the function control.
5. LCR \ RPT \ 4
LCR: Last Channel Recall. Press the LCR button to
return to the last frequency that was transmitted on for
more than 3 seconds.
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RPT: Repeater Access Tone. Most repeaters require
an 88.5 Hz tone burst to access. To activate the 88.5
Hz tone burst, press the FUNC control and then press
the RPT button. RPT will appear on the LCD indicating
that the tone burst will now automatically be transmitted whenever the PTT is pressed. To deactivate, repeat the same process.
To stop scanning, press the SCAN button, or momentarily press the PTT button on the microphone (scanning will stop without transmitting).
SHIFT: Shift Offset. Used for programming offsets to
operate repeater networks. The 257 can transmit and
receive on different frequencies.
4: Memory Channel 4. After programming this button
is memory channel 4. See M.LOAD \ M.SAVE control
for programming instructions.
6. CALL \ 2
CALL: The call frequency is 29.300 MHz, FM. The
radio’s operating frequency and mode is automatically
reset to this when the CALL button is pressed.
2: Memory Channel 2. After programming this button
is memory channel 2. See M.LOAD \ M.SAVE control
for programming instructions.
7. MODE \ T. LOW \ 5
MODE: Operating Mode. Press the MODE control to
select the operating mode. The operating mode is indicated on the liquid crystal display: AM, FM, USB, or
LSB.
T. LOW: Tone Low. Press the FUNC button, and then
press the T. Low button to turn on the receive audio
tone control. LOW will appear on the LCD when the
low tone is activated. This feature will roll-off high frequency noise (i.e. “white” noise). Under many operating conditions this will improve the clarity and understanding of received signals.
To program the offset, press the FUNC button and hold
down the SHIFT button for 3 or more seconds. Three
digits will appear on the LCD. This is the offset frequency in kHz. Rotate the FREQUENCY control until
the desired offset frequency is displayed. To return to
the main display press the FUNC button and hold down
the SHIFT button for 3 or more seconds, or momentarily press the PTT button on the microphone (the
transmitter will not be engaged).
To activate the programmed offset frequency, press
the FUNC button, and then press the SHIFT button
once. +SHIFT is displayed on the LCD. The 257 will
now transmit on the frequency that is XXX kHz greater
than the displayed, or receive, frequency (XXX represents the programmed offset frequency in kHz).
To transmit on the frequency that is XXX kHz lower
than the displayed, or receive, frequency press FUNC,
then the SHIFT button. Repeat this until -SHIFT is displayed on the LCD.
To disengage the programmed offset frequency, press
the FUNC button and then press the SHIFT button.
Repeat this until the SHIFT indicator is no longer displayed on the LCD.
5: Memory Channel 5. After programming this button
is memory channel 5. See M.LOAD \ M.SAVE control
for programming instructions.
8. SCAN \ SHIFT \ 3
SCAN: Frequency Scan. Scans in increments of 10
kHz. There are two ways to scan using the front panel
controls.
(1) Receive Audio On Scanning: Press the SCAN button. Scan rate is one step every 5 seconds. To stop
scanning press the SCAN button again, or momentarily press the PTT button on the microphone (scanning will stop without transmitting).
(2) Receive Audio Mute Scanning: Carefully rotate the
squelch control a minimum excursion (refer to 14) until
the receive audio is off. The receiver scan rate will now
be five frequencies per second. When a signal is detected the squelch is automatically disengaged and the
scanning is paused. The squelch circuit will automatically re-engage and the receiver will continue to scan
the moment the received signal is no longer detected.
3: Memory Channel 3. After programming this button
is memory channel 3. See M.LOAD \ M.SAVE control
for programming instructions.
9. M.SAVE \ M.LOAD
M.SAVE: Memory Save. To save in memory a specific
frequency and operating mode, select the desired mode
and rotate the FREQUENCY control to the desired frequency. Press the FUNC button, and then press the
M.SAVE button. S will appear on the LCD next to the
frequency. While S is displayed, immediately press any
of the memory channel buttons (1 - 5). The mode and
frequency is now saved into memory. If the S indicator
disappears before you press the memory channel button, the information will not be saved and the process
must be repeated.
M.LOAD: Memory Load (Recall). To load, or recall,
any of the saved memory channels press the M.LOAD
button. L will appear on the LCD for several seconds.
While the letter is displayed press the desired memory
channel button (1 - 5). The programmed mode and frequency will be displayed.
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10. CLAR \ FUNC
CLAR: Clarifier. The clarifier shifts both the TX and
RX frequency 1.5 kHz each side of the center frequency. This is necessary for tuning to an SSB signal.
Rotate the clarifier control clockwise or counterclockwise to tune an SSB signal.
FUNC: Function. This control is used to operate the
six control buttons on the front panel that are printed in
blue. Press slightly and release, FUNC will be displayed
on the LCD indicating that the function command is
activated. After you have pressed one of the buttons
the FUNC will disappear from the screen.
11. FREQ: Frequency. Rotate clockwise or counterclockwise to select the desired frequency.
12. OFF / VOLUME
OFF: Turns the power to the radio on and off.
VOLUME: Adjusts the AF gain, or volume of the re-
ceived audio. Turn clockwise to increase and counterclockwise to decrease.
OTHER FEATURES
1. PROGRAMMING TONE
This tone sounds each time the CPU is being programmed. It is helpful, in the beginning so you can be
sure the command has been entered. You may eliminate the tone by simply pressing the PTT switch on the
microphone and turning on the ON/OFF POWER switch
at the same time.
2. Memory Back Up
The 257 features a super-capacitor back up for the 5
memory channels. The 257 can be disconnected from
a power source for approximately 4 or 5 days before
the memory is lost.
14. SQ: Squelch. Used to eliminate background or “white”
noise when monitoring strong signals. Also used to
activate SCAN feature (refer to 8). To properly adjust
squelch circuit, start rotating the control slowly clockwise until the received white noise disappears.
15. PWR: Variable RF Output Power. Rotate clockwise to
increase RF output power. Rotate counterclockwise to
decrease RF output power.
Variable RF output power allows low power transmitting for QRP operation in compliance with the FCC request for reduced signal strength during periods when
propagation levels are high.
16. Push-To-Talk Switch: Press and hold the switch to
transmit. TX will appear on the LCD screen when transmitting. Release the switch to receive.
17. UP / DN: Up and Down Frequency Controls. Press the
UP control to increase in frequency. Press the DN control to decrease in frequency.
REAR PANEL
1. External Speaker Jack
An external speaker jack is located on the rear panel
of the transceiver. The Magnum 257 is designed to
accept any standard 8 ohm external speaker for use
with two-way transceivers.
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GENERAL SPECIFICATIONS
Frequency Coverage : Transmit and Receive ...................................... 28.000 to 29.699 MHz
Antenna Impedance : 50 ohm, unbalanced
Frequency Control : Digital Phase-Lock Loop (PLL) Synthesizer
Frequency Accuracy : Better than +10 ppm from 0 - 40 0C after 15 min. warm up
Power Requirement : 12 - 13.8 V DC, negative ground
Current Consumption : 6 amps maximum
Dimensions : 6 x 2 x 9.5 in (W x H x D)
Weight : 2.9 lbs
TRANSMITTER SPECIFICATIONS
Power Output : SSB / FM...............................................................................30 Watts
: AM ...................................................9 Watts Average / 30 Watts PEP
Tuning Steps : 1 kHz / 10 kHz / 100 kHz
Final Transistors : 2SC1969 (x2)
Spurious Emissions : More than 50 dB below peak output power
Carrier Suppression : More than 40 dB below peak output power
Unwanted Sideband : More than 50 dB below peak output (1 kHz tone)
FM Deviation : +/- 2 kHz maximum
Audio Response : More than 30dB below peak output
Frequency Response : 400 to 2800 Hz
Microphone Impedance : ECM, 600 to 1K ohms
RECEIVER SPECIFICATIONS
Circuit Type : Dual-Conversion Superheterodyne
Intermediate Frequencies : 1st IF / SSB IF..................................................................10.695 MHz
: 2nd IF..................................................................................... 455 kHz
Sensitivity : SSB............................................................. 0.25 µV at 10 dB S + N/N
: AM ................................................................ 1.0 µV at 10 dB S + N/N
: FM...................................................................0.3 µV at 12 dB SINAD
Selectivity : SSB................................................ 4.2 kHz (-6 dB) / 8.5 kHz (-60 dB)
: AM / FM .......................................... 6.0 kHz (-6 dB) / 18 kHz (-60 dB)
Clarifier Range : +/- 1.5 kHz
Adjacent Channel Rejection : Better than 70 dB
IF Rejection : Better than 80 dB for all frequencies
Frequency Response : 250 to 3000 Hz
Audio Output Power : 2 watts minimum at 10% THD with an 8 ohm load
Audio Output Impedance : 8 ohms
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MAGNUM INTERNATIONAL
A Division of RF Limited
PO Box 445 • Issaquah WA 98027
Telephone 425-558-9592 • Facsimile 425-558-9704
Technical Support Only 1-877-MAGNUM-9 (1-877-624-6869)
http://www.MagnumRadio.com
E-Mail info@MagnumRadio.com
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