U20570 Used MFJ-557 Deluxe Morse Code Practice Oscillator

U20570 Used MFJ-557 Deluxe Morse Code Practice Oscillator 

This pre-owned MFJ-557 Deluxe Morse Code practice oscillator is in good overall condition, showing light signs of handling and superficial storage dust across the baseplate and speaker housing. The integrated heavy-duty straight key is clean and intact, featuring smooth chrome-plated brass hardware, silver contact points, and an ergonomic black navy-style knob. The top-mounted Volume and Tone control dials turn smoothly with positive mechanical resistance. On the left side of the oscillator housing, the DC 12V coaxial power jack and 3.5mm Earphone jack are physically solid, straight, and clean.

The MFJ-557 is an all-in-one CW training station that combines a classic straight key with a built-in solid-state audio oscillator and speaker mounted on a non-skid baseplate. Designed for aspiring amateur radio operators, seasoned contesters, and CW enthusiasts, it allows hands-on Morse code sending practice without keying a live transmitter. The integrated key assembly features fully adjustable contact spacing, pivot tension, and spring return, allowing operators to tailor the mechanical travel and feel precisely to their touch. Top-panel rotary controls provide variable volume from whisper-quiet to room-filling sound, as well as an adjustable sidetone pitch ranging from high-frequency tones to low-pitch thuds. Equipped with an earphone output for private practice and capable of operating from an internal 9V battery or external 12V DC adapter, the MFJ-557 is an essential desktop practice aid for mastering code speed and rhythm.

Condition

• Cosmetic Condition: Good pre-owned condition overall, displaying minor handling marks and light storage dust on the black metal base and plastic oscillator casing.

• Key Mechanism: The straight key mechanism, pivot bar, knurled thumb screws, contact points, and navy knob are in solid mechanical shape.

• Controls & Dials: Top Volume and Tone potentiometers rotate smoothly without binding.

• Jacks & Interfacing: The side 12V DC barrel socket and 3.5mm earphone/headphone jack are clean and tight.

Key Features

• All-in-One CW Training Station: Combines an adjustable straight key, audio oscillator, and internal loudspeaker on a single rigid baseplate.

• Fully Adjustable Straight Key: Dual knurled brass adjustment screws allow precise calibration of contact spacing, return spring tension, and arm travel.

• Variable Volume & Tone: Independent rotary dials let you customize both the volume level and audio sidetone pitch to match your listening preference.

• Private Practice Earphone Jack: Standard 3.5mm output silences the internal speaker for quiet headphone listening.

• Dual Power Flexibility: Operates via an internal 9V battery or an external 12V DC power source via the side coaxial jack.

• Heavy Anti-Skid Base: Weighted base with rubber feet prevents sliding on the desk while practicing sending rhythms.

What's Included

• MFJ-557 Deluxe Morse Code Practice Oscillator with Integrated Straight Key (Battery Not Included)

Comes With Our 90-Day Warranty!

Serial Number: N/A 

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