Model MFJ-9412
INSTRUCTION MANUAL
VERSION 1A
CAUTION: Read All Instructions Before Operating Equipment
MFJ ENTERPRISES, INC.
300 Industrial Park Road
Starkville, MS 39759 USA
Tel: 662-323-5869 Fax: 662-323-6551
COPYRIGHT 2013 MFJ ENTERPRISES, INC.
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MFJ-9412 Instruction Manual 12-Meter SSB Transceiver
INTRODUCTION
Congratulations on your choice of the MFJ-9412 Twelve-Meter SSB Transceiver. Please
read the whole manual carefully before attempting to operate your new radio. Let's begin
with an introduction to some special features we think you'll like!
Easy to Operate: No microprocessors, no booting up -- just turn it on and tune in!
Potent Signal: Exclusive Constant CurrentTM syllabic speech processing adds 4 to 6 dB
of intelligibility to your signal to cut through noise, fading, and QRM.
Low Drain: Operate from a 3-Amp AC supply or 12-Volt battery. All-analog circuitry
means high energy efficiency!
Hot Receiver: Low-noise preamp and active-DBM front end dig deep into the noise
floor to capture the weak ones. If the signal's there, you'll copy it.
Excellent Selectivity: Sharp 2.4 KHz wide 10-MHz SSB ladder filter reduces passband
noise, fights QRM, and improves transmitter intelligibility.
Great Suppression: Multiple tuned circuits and a 7-element lowpass filter keep your
signal clean and free from unwanted interference.
Real S-Meter: Steer your beam with pin-point accuracy and give meaningful signal
reports with a full-size analog meter. Also, monitor speech processing level.
Agile Tuning: No abrupt tuning-rate chages or stair-stepping. Reduction-drive analog
VFO lets you scan the band quickly, yet zero in on SSB signals smoothly. Great for
hunt-and-pounce contest operation!
Impressive Audio: A special BTL audio amplifier IC paired with a rugged 3-1/2" topmount speaker deliver robust audio with unusual clarity.
Phone Jack: 1/4" jack accepts stereo or monoral headphones and cuts off the speaker
automatically. Attenuated output protects your ears and makes gain adjustment easy.
Amplifier Jack: Solid-state FET switch with a RCA jack to key an external amplifier.
Built to Last: You get conservative design paired with quality components and a
premium-grade SMT pc board -- all protected by a tough aluminum case and capped with
a handsome stainless steel front panel. Built tough for years of dependable service.
At home or traveling the world, you'll enjoy superb 12-meter performance with your
MFJ-9412. Best of all, it's fully backed by MFJ's exclusive NO MATTER WHATTM oneyear guarantee. If it breaks, we'll take care of it.
GENERAL DESCRIPTION
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MFJ-9412 Instruction Manual 12-Meter SSB Transceiver
The MFJ-9412 monoband transceiver is designed especially for fixed or portable radio
communication via the twelve-meter amateur band. Energy-efficient analog circuitry and
syllabic speech processing deliver superior on-air performance while conserving valuable
energy. The MFJ-9412 uses a single-conversion mixing format and a low-noise
heterodyne VFO for enhanced weak-signal performance. The transmitter stages provide
tuned inter-stage coupling and a built-in 7-element lowpass filter to suppress interference
at TV and FM-broadcast entertainment frequencies. Other features include a sharp
communication-grade crystal IF filter, built-in heavy-duty speaker, fully-analog
mechanical S-meter, optional semi-break-in CW module, and intuitive controls.
Typical Specifications
Receiver Section:
Frequency Coverage:.....................................24.890-24.990 MHz
Mode:.............................................................USB
Receiver Type:...............................................Single-conversion Superhet
Frequency Control: ........................................6-MHz VFO mixed to 34.9 MHz
IF Frequency:.................................................10 MHz
IF Selectivity:.................................................-6 dB @ 2.4 KHz
AGC:..............................................................Audio-derived, 70-dB dynamic
range
Sensitivity: ......................................................15 uV for 12-dB S/N
Audio: ............................................................500 mW into 8 Ohms at 10% THD
Average Receive Current Drain:....................60-mA with S-meter lamp disabled
Transmitter Section:
Typical RF Power Output:.............................12 Watts PEP
Mode..............................................................USB
VSWR Tolerance:..........................................3:1 VSWR maximum
Peak TX Current:...........................................3.0 Amps
Speech Enhancement:....................................RF-compression, syllabic rate
Spurious Attenuation:....................................-60 dBc typical
Mic Input: ......................................................600-Ohm dynamic
*CW operation possible within the 24.89 to 24.930 range with an optional CW adapter board.
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MFJ-9412 Instruction Manual 12-Meter SSB Transceiver
QUICK-START OPERATING INSTRUCTIONS
• Power Supply: Use any regulated 13.8-Volt 3-Amp supply or comparably-rated 12-
Volt battery. Connect power via a 5.5 OD x 2.1 mm coaxial power plug (Radio Shack
274-1569): [+] lead must be attached to the connector center pin.
+
-
• Microphone: The MFJ-290 dynamic microphone compliments your radio's speech
processor, but other 600-ohm PTT microphones may be used with a 5-pin DIN
connector installed as shown below (use Radio Shack 274-003). Amplified
microphones should not be used with the MFJ-9412.
Pin 3 = PTT Line
Pin 4 = Mic Line
Pin 1,2,5 = Ground
1
4
3
5
2
Mic
PTT
Gnd
• Antenna Selection: Use any vertical or horizontal 12-meter antenna exhibiting a
VSWR of 2:1 or less. A simple dipole or groundplane is adequate for casual
operation, but a 3-element yagi or 2-element quad yields better DX performance.
Important Note: Avoid using antennas with unknown or high VSWR. The MFJ-9412
does not provide automatic high-VSWR shutdown circuitry. Operation into extremely
reactive loads may result in out-of-band spurious emissions in violation of FCC rules!
• Speech Processing: The MFJ-9412 processor rapidly readjusts transmitter IF gain for
each spoken syllable. For best results, hold the Mic about 1-2" from your lips and
speak normally. The S-meter should deflect 1/2 scale as you speak.
Important Note: Transmit meter deflection will be affected by high-VSWR loads. If the
meter deflects beyond S9 or holds below S4 with normal speech, check your antenna. A
VSWR of 2:1 or less is normally considered acceptable for amateur service.
• Connecting a Power Amplifier: The MFJ-9412 provides a built-in FET switch to
key an external amplifier. Be sure to follow all manufacturer's instructions carefully
when installing an amplifier at your station. The Ext Amp jack provides closure to
ground during transmit.
• Choosing an Operating Location: Set your station up in a sheltered and dry
location. Avoid operating in direct sunlight--the radio's black case may absorb
excessive heat that can impair normal operation or damage internal components.
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