Magnum 257 User manual

MAGNUM 257
OPERATING MANUAL

Copyright © 1999 by Magnum International. All rights reserved.

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
toprovide years ofenjoymentandtrouble-freeservice. There aremanyfeaturesand 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 op-
tions. 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.
Someof the features ofthe257are; an advanced designliquidcrystaldisplaythat provides theoperatorwith
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.
IMPORTANT : The Magnum 257 is designed for amateur radio use. If the transmitter is operated in the
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.
American Radio Relay League (ARRL)
225 Main Street
Newington, CT 06111
Telephone[phone]
Facsimile860-594-0259
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
receiptwithin 15 days fromthepurchasedate. If the warrantyregistrationformandcopy of yoursalesreceipt
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:
MagnumInternational
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 follow-
ing 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
2. Microphone Hanger
The microphone hanger may be attached to the side
ofthetransceiver, or anyotherconvenientlocation.Use
the provided screws to attach the microphone hanger
either vertically or horizontally to the side of the trans-
ceiver.
3. Mounting
When attaching the 257 mounting bracket to the ve-
hicle, choose a location that will provide easy access
to all front panel controls and air circulation to the rear
panel.When selecting a mountinglocation,makesure
that there is ample space behind the control deck for
thecables. Do not pinch,orbendsharply, thepoweror
antenna cables. Do not install the 257 in any compart-
ment that restricts airflow and do not install in a loca-
tion that interferes with the safe operation of the ve-
hicle.
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 an-
tenna 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,worngenerator/alternator,orpoor voltage regu-
latorwill seriously impair theperformanceofthe trans-
ceiver. 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 sys-
tem are in good condition prior to installing the trans-
ceiver.
CAUTION!
VOLTAGE EXCEEDING 15 VDC WILL DAMAGE
THERADIO.MEASUREVOLTAGE ATBATTERY
TERMINALS, WITH VEHICLE RUNNING, PRIOR
TO INSTALLATION!
Before making any electrical connections make sure
the AF gain (volume) control on the control deck is in
the “OFF” position.
Connectthe positive (+) redwireofthe 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
thetransceiveris disconnected when thevehicleisoff.
Thiswilleliminatethepossibility ofthetransceiverdrain-
ing the vehicle’s battery.
Connect the negative (-) black wire to a metal part of
thevehicle’sframe, or chassisground.Make sure that
this is a good ground connection.
The257 power cordmayalso be connecteddirectlyto
the battery. Connecting directly to the battery has sev-
eral benefits, the first of which is to maximize RF out-
put.Secondly, thebatteryisa very largecapacitorand
willhelp eliminate certain typesofambientandvehicle
noise.Ifconnecting directly to the vehicle’sbattery,ad-
ditional power cable may be required. On runs of 8
feetorlessuse14-gaugestrandedwire.Use12-gauge
wire on longer runs.
5. Antenna Connection
The transceiver will operate using any standard 50-
ohm ground-plane, vertical, mobile whip, long wire or
similar antenna. The antenna should be rated at 50
wattsPEPminimum.A standard SO-239 type antenna
connectoris located on therearpanelof the 257. Con-
nection is made using a PL-259 and high grade co-
axial cable (RG213, RG58A/U or Mini RG-8 is recom-
mended).
Aground-planeantennaprovidesgreatercoverage 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 un-
der 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 an-
tennasusesthe metal vehicle bodyasagroundplane.
Oncethe antenna is mountedonthevehicle, route the
coaxial cable so that it is not next to any power cables
or vehicle cables. Connect the PL-259 to the antenna
connectoron the rearpanelofthe257. Make surethat
thecables does not interferewiththesafe 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 per-
forming properly the VSWR should never exceed 1.5
to1. Never transmitonanyantenna system wherethe

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VSWR exceeds 1.8 to 1. This will stress the output
stageandcould destroy the RFtransistors;thistypeof
misuse and failure is not covered under warranty.
MeasuretheVSWRatthecenterofthe operatingband.
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
frequencyof the transceiver.If the antenna hasa wide
enough frequency range and band-pass, the VSWR
readings should be below 1.5 to 1 across the entire
operatingband. If at the lowerorupperendofthetrans-
ceiveroperatingfrequency,theVSWRmeasuresmore
than 1.5 to 1, it is recommended that the antenna be
re-tuned before operating on those frequencies.
Ifyouareexperiencingunusual VSWR readings check
for the following possible problems:
1) Make sure that the antennaisinstalledproperlyand
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
Incertain vehicle installations,electrical noise orinter-
ferencemaybepresentinthereceiveaudioofthetrans-
ceiver. 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
alternatornoise or ignition noise filtercanbepurchased
and installed according to the manufacturer’s instruc-
tions. 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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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
microphoneamplifiercircuit.The gain increases as the
controlisrotatedclockwise.Foroptimumsetting,press
the push-to-talk (PTT) switch on the microphone, ad-
just the mic gain control until all segments of the S/RF
display are lit. Next, rotate the control counterclock-
wiseuntil thelastsegmentofthedisplay startstoflicker.
TheS/RF display isthe bar graphlocated on thelower
edge of the LCD screen.
3. RF GAIN CONTROL
Adjuststhe receiversensitivitytoboth signalsandback-
ground noise. This affects the distance at which a sig-
nal can be detected. Turning the control counterclock-
wise reduces the receiver sensitivity. This is particu-
larlyusefulin areas where largevolumes of traffic (sig-
nals) are present. The S/RF display indicates the re-
ceived signal’s strength. The S/RF display is the bar
graph located on the lower edge of the LCD screen.
IMPORTANT!
Operating some of the features in 4 through 9 re-
quire 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.
2
3
4101
5
6
7
8
9
11
16 17 12 13 1514
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
flashonandoff.Press theSTEPbuttonagaintochange
steppingresolution.
To tune frequencies in either 10 kHz or 100 kHz incre-
ments, press the STEP button until the desired digit is
flashing. Rotate the FREQUENCY control in either di-
rection.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
untilthe1 kHz digit flashes onand off. Rotate the FRE-
QUENCY control. NOTE: When stepping in 1 kHz in-
crements, 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 acti-
vate 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.
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
theRPTbutton. RPT will appearon the LCD indicating
that the tone burst will now automatically be transmit-
ted whenever the PTT is pressed. To deactivate, re-
peat the same process.
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’soperating frequency and modeis 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
selecttheoperating mode. The operating modeis indi-
cated 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 fre-
quency noise (i.e. “white” noise). Under many operat-
ing conditions this will improve the clarity and under-
standing of received signals.
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 but-
ton. Scan rate is one step every 5 seconds. To stop
scanning press the SCAN button again, or momen-
tarily press the PTT button on the microphone (scan-
ning will stop without transmitting).
(2)Receive Audio MuteScanning: Carefully rotatethe
squelchcontrol a minimum excursion(refer to 14) until
thereceiveaudio is off. Thereceiver scan rate willnow
be five frequencies per second. When a signal is de-
tectedthesquelchisautomaticallydisengagedandthe
scanning is paused. The squelch circuit will automati-
cally re-engage and the receiver will continue to scan
the moment the received signal is no longer detected.
To stop scanning, press the SCAN button, or momen-
tarily press the PTT button on the microphone (scan-
ning will stop without transmitting).
SHIFT: Shift Offset. Used for programming offsets to
operate repeater networks. The 257 can transmit and
receive on different frequencies.
Toprogramtheoffset,presstheFUNCbuttonandhold
down the SHIFT button for 3 or more seconds. Three
digits will appear on the LCD. This is the offset fre-
quency in kHz. Rotate the FREQUENCY control until
the desired offset frequency is displayed. To return to
themain display press the FUNC button and hold down
the SHIFT button for 3 or more seconds, or momen-
tarily 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
nowtransmit on the frequencythat is XXXkHz greater
than the displayed, or receive, frequency (XXX repre-
sents the programmed offset frequency in kHz).
To transmit on the frequency that is XXX kHz lower
thanthedisplayed, or receive, frequencypress FUNC,
then the SHIFT button. Repeat this until -SHIFT is dis-
played on the LCD.
Todisengagetheprogrammed offset frequency, press
the FUNC button and then press the SHIFT button.
Repeat this until the SHIFT indicator is no longer dis-
played on the LCD.
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. Tosave in memory aspecific
frequencyandoperatingmode,select thedesiredmode
androtatethe FREQUENCY control tothe desired fre-
quency. 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
frequencyis now savedinto memory. Ifthe Sindicator
disappearsbefore you press thememory channel but-
ton, the information will not be saved and the process
must be repeated.
M.LOAD: Memory Load (Recall). To load, or recall,
anyof the saved memorychannels press theM.LOAD
button. L will appear on the LCD for several seconds.
Whilethe letter is displayedpress the desiredmemory
channelbutton(1 - 5). The programmedmode and fre-
quency 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 fre-
quency. This is necessary for tuning to an SSB signal.
Rotate the clarifier control clockwise or counterclock-
wise to tune an SSB signal.
FUNC: Function. This control is used to operate the
sixcontrol buttons on thefront panel thatare printed in
blue.Press slightlyandrelease,FUNC will bedisplayed
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 counterclock-
wise 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 counter-
clockwise to decrease.
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 clock-
wise until the received white noise disappears.
15. PWR: Variable RF Output Power. Rotate clockwise to
increaseRFoutput power. Rotate counterclockwiseto
decrease RF output power.
Variable RF output power allows low power transmit-
ting for QRP operation in compliance with the FCC re-
quest 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 trans-
mitting. Release the switch to receive.
17. UP / DN: Up and DownFrequency Controls.Press the
UPcontroltoincrease in frequency. Press theDNcon-
trol 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.
OTHER FEATURES
1. PROGRAMMING TONE
This tone sounds each time the CPU is being pro-
grammed. It is helpful, in the beginning so you can be
sure the command has been entered. You may elimi-
natethetone by simply pressing thePTT switch on the
microphoneandturningon theON/OFFPOWERswitch
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.

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GENERAL SPECIFICATIONS
Frequency Coverage : Transmit and Receive ...................................... 28.000 to 29.699 MHz
AntennaImpedance : 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
UnwantedSideband : 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
MicrophoneImpedance : ECM, 600 to 1K ohms
RECEIVER SPECIFICATIONS
Circuit Type : Dual-Conversion Superheterodyne
IntermediateFrequencies : 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

MAGNUM INTERNATIONAL
A Division of RF Limited
PO Box 445 • Issaquah WA 98027
Telephone [phone] • Facsimile 425-558-9704
Technical Support Only 1-877-MAGNUM-9 (1-877-624-6869)
http://www.MagnumRadio.com
E-Mail [email protected]