---
product_id: 739824039
title: "MFJ Enterprises Original MFJ-557 Deluxe Morse Code Practice Oscillator Straight Key w/Volume Control by MFJ"
brand: "mfj"
price: "$1150196"
currency: COP
in_stock: false
reviews_count: 1
category: "Mfj"
url: https://www.desertcart.co/products/739824039-mfj-enterprises-original-mfj-557-deluxe-morse-code-practice-oscillator
store_origin: CO
region: Colombia
---

# Compact size: 8.5" x 2.25" x 3.75" Dual power options: 9V battery or 110VAC Adjustable volume control for perfect tone MFJ Enterprises Original MFJ-557 Deluxe Morse Code Practice Oscillator Straight Key w/Volume Control by MFJ

**Brand:** mfj
**Price:** $1150196
**Availability:** ❌ Out of Stock

## Summary

> 📡 Master Morse Like a Pro — Stay Connected, Stay Ahead!

## Quick Answers

- **What is this?** MFJ Enterprises Original MFJ-557 Deluxe Morse Code Practice Oscillator Straight Key w/Volume Control by MFJ by mfj
- **How much does it cost?** $1150196 with free shipping
- **Is it available?** Currently out of stock
- **Where can I buy it?** [www.desertcart.co](https://www.desertcart.co/products/739824039-mfj-enterprises-original-mfj-557-deluxe-morse-code-practice-oscillator)

## Best For

- mfj enthusiasts

## Why This Product

- Trusted mfj brand quality
- Free international shipping included
- Worldwide delivery with tracking
- 15-day hassle-free returns

## Key Features

- • **Compact & Portable:** Sleek design fits easily on any desk or in your kit
- • **Versatile Power Modes:** Use on-the-go with 9V battery or plug in for steady practice
- • **Precision Volume Control:** Customize your Morse code tone to suit any environment
- • **Trusted Brand Reliability:** Backed by MFJ’s renowned one-year warranty
- • **Ideal for Serious Learners:** Perfect for honing your Morse skills with professional-grade quality

## Overview

The MFJ-557 Deluxe Morse Code Practice Oscillator is a compact, reliable device designed for serious Morse code enthusiasts. It operates on either a 9V battery or 110VAC power, features adjustable volume control for clear signal modulation, and comes with a one-year warranty from MFJ Enterprises. Perfect for professionals and hobbyists aiming to sharpen their telegraphy skills with precision and convenience.

## Description

Run the mfj-557 Deluxe Morse Exercise Oscillator with a 9-volt battery (not included) or 110 VAC Measures 8 1/2" x 2 1/4" x 3 3/4" Famous mfjs One Year Warranty

Review: 電鍵は自作でしたので、今年見た目が良かったので購入してみました、が電源がなかったので別に購入する事になりました、さて、使った感想ですが、発信音は変調出来るのでとても良いです、電鍵は思っていたより安っぽくて、自分の電鍵を付けて使用してます、

## Features

- Exercise Oscillator Electric Key MFJ Company Original Morse Signal Mfj-557 Deluxe W/Volume Control

## Technical Specifications

| Specification | Value |
|---------------|-------|
| ASIN | B00OAHNA10 |
| Amazon Bestseller | #135,998 in Musical Instruments ( See Top 100 in Musical Instruments ) #1,981 in Music Tuning Accessories |
| Batteries Included | No |
| Customer Reviews | 4.2 4.2 out of 5 stars (2) |
| Date First Available | October 29, 2014 |
| Model Number | MFJ-557 |
| Product Dimensions | 21.59 x 9.53 x 5.72 cm; 571.53 g |

## Product Details

- **Brand:** MFJ
- **Item Weight:** 572 g
- **Mounting Type:** Tabletop Mount
- **Number of Blades:** 3
- **Number of Speeds:** 3
- **Power Source:** Battery Powered
- **Special Feature:** Oscillating
- **Style:** Modern
- **Voltage:** 9 Volts

## Images

![MFJ Enterprises Original MFJ-557 Deluxe Morse Code Practice Oscillator Straight Key w/Volume Control by MFJ - Image 1](https://m.media-amazon.com/images/I/71AR8HeZlyL.jpg)
![MFJ Enterprises Original MFJ-557 Deluxe Morse Code Practice Oscillator Straight Key w/Volume Control by MFJ - Image 2](https://m.media-amazon.com/images/I/71CSErlhoRL.jpg)
![MFJ Enterprises Original MFJ-557 Deluxe Morse Code Practice Oscillator Straight Key w/Volume Control by MFJ - Image 3](https://m.media-amazon.com/images/I/71GbGfy53KL.jpg)
![MFJ Enterprises Original MFJ-557 Deluxe Morse Code Practice Oscillator Straight Key w/Volume Control by MFJ - Image 4](https://m.media-amazon.com/images/I/819mwLtjgTL.jpg)
![MFJ Enterprises Original MFJ-557 Deluxe Morse Code Practice Oscillator Straight Key w/Volume Control by MFJ - Image 5](https://m.media-amazon.com/images/I/81qnbfVlryL.jpg)

## Questions & Answers

**Q: It says practice machine; can it be used in real life applications? If not would you recommend a unit that would?**
A: The key can be removed from the practice oscillator base, and hooked up to most CW transceiver / transmitters for real world applications after you are done using it for audible practice .

**Q: can you hook  paddles up instead of the straight key ?**
A: You can not. Paddles need additional intelligence and an additional circuit that will send dots or dashes when you move the paddles right or left. This is essentially like the buzzer on a door...as long as you press it buzzes, when you stop it stops.

**Q: Can this transmit**
A: Yes, you could transmit with it, but straight keys are so cheap why not just buy another one.

**Q: can you wire this to a radio**
A: Dear Writer, 10x 4 msg. You can do if your radio has MORSE key wire's input (not morse key speaker input). Simply un-screw two wires which connects to morse key from inbuilt MFJ device then connect radio's morse key wires. Have a g8t day. 73. Mayank Gupta (VU3MFT)

## Customer Reviews

### ⭐⭐ Review
*by 櫛***治 on June 10, 2020*

電鍵は自作でしたので、今年見た目が良かったので購入してみました、が電源がなかったので別に購入する事になりました、さて、使った感想ですが、発信音は変調出来るのでとても良いです、電鍵は思っていたより安っぽくて、自分の電鍵を付けて使用してます、

## Frequently Bought Together

- MFJ Enterprises Original MFJ-557 Deluxe Morse Code Practice Oscillator Straight Key w/Volume Control
- Learn Morse Code - Easy Tutorial Workbook for Beginners: The Easiest Way to Study Morse - LISTEN to Morse Signals with QR Codes! Morse Practice Book for Kids Ages 8+ and Adults
- Morse Code Operating for Amateur Radio – Your Guide to Ham Radio’s First Language

---

## Why Shop on Desertcart?

- 🛒 **Trusted by 1.3+ Million Shoppers** — Serving international shoppers since 2016
- 🌍 **Shop Globally** — Access 737+ million products across 21 categories
- 💰 **No Hidden Fees** — All customs, duties, and taxes included in the price
- 🔄 **15-Day Free Returns** — Hassle-free returns (30 days for PRO members)
- 🔒 **Secure Payments** — Trusted payment options with buyer protection
- ⭐ **TrustPilot Rated 4.5/5** — Based on 8,000+ happy customer reviews

**Shop now:** [https://www.desertcart.co/products/739824039-mfj-enterprises-original-mfj-557-deluxe-morse-code-practice-oscillator](https://www.desertcart.co/products/739824039-mfj-enterprises-original-mfj-557-deluxe-morse-code-practice-oscillator)

---

*Product available on Desertcart Colombia*
*Store origin: CO*
*Last updated: 2026-01-24*