About this product

Product Information

The MFJ-557 is a Deluxe Morse Code Practice Oscillator straight key model developed by the MFJ Enterprises brand. It has a contact pushed to create and send the practice message, and it has dimensions of 3.75-inches by 2.75-inches, which makes it compact and easy to carry. The radio and communication device is handy in learning the coded language which is useful for sending short messages.

Product Identifiers

BrandMFJ

GTIN0702646177954

UPC0702646177954

eBay Product ID (ePID)1737650127

Product Key Features

Year ManufacturedEasy to use

Compatible BrandFor Drake, For RadioShack, For Collins, For Icom, For Kenwood, For Elecraft, For Ranger, Universal, For Galaxy, For Yaesu, For Ten-Tec, For Wouxun, For Heathkit, For Realistic, For Hallicrafters

FeaturesBuilt-In Headphone Jack, Volume controls

Compatible ModeleBay US

Dimensions

Height2.25in

Width3.75in

Item Weight1.25 lbs

Ratings and Reviews

Learn more

4.9

28 product ratings

26 users rated this 5 out of 5 stars
1 users rated this 4 out of 5 stars
1 users rated this 3 out of 5 stars
0 users rated this 2 out of 5 stars
0 users rated this 1 out of 5 stars

Would recommend

Good value

Good quality

Most relevant reviews

See all 24 reviews

by murpee0
Nov 05, 2019Top favorable review
Well designed and very rugged.
This is a very rugged unit. I do like the rubber skid pads that help to grip on flat surfaces. The unit assembles easily. It is great for ''gadget'' type hobbyists, yet I did MC in the military, and this is the genuine article.
Verified purchase: YesCondition: New
by 94bond
Jan 13, 2017Top critical review
fine key, ugly oscillator
I'm pleased with the key, but not with the sound of the oscillator. Each beep descends rapidly in pitch, with the result that even perfectly keyed morse code sounds a little drunk. The tone is also raspy and harsh (triangle wave). I checked some YouTube videos, and it seems these traits are typical of this model, although not all descend in pitch as much as mine does. My oscillator is so repulsive to my ear that I ended up buying a serial to usb conversion cable so I could use software on my computer to generate the sound. If I had known the oscillator was going to be like this then I probably would have purchased a higher quality key without an oscillator.
Verified purchase: YesCondition: New
by niog_58
Feb 05, 2023
Nice little self contained morse key.
Morse key with adjustable gap and tension. Volume and tone button. Takes a 9v battery. Reasonable sturdiness and weight. Decent quality for price and an all in unit for anyone who just wants to either learn morse or practice morse.
Verified purchase: YesCondition: Pre-owned
by jihus-36
Oct 03, 2018
GREAT Product!!!!!
This device has really helped me to send Morse Code much better. After listening to my coding, I have recognized several issues that I need to address to send more consistent cod. Thank you for a wondedrful product. -Dave H,
Verified purchase: YesCondition: New
by lada1467
May 05, 2021
Works great
Works great, heavy enough to not move around, rubber pads prevent scratching surfaces. I see no need for a separate power supply, the battery is lasting a long time.
Verified purchase: YesCondition: New
by 1st-case
Aug 24, 2017
MJF-557 Straight Key
The MFJ-557 Morse Code straight key is a great product at a very reasonable price. It can used for practice as a stand alone keyer or contacted directly to radio for CW generation. I recommend the MJF-557 for any level ham operator. Thank you for this very versatile product. Ron Case KG5TNS
Verified purchase: YesCondition: New
by DmwRC9eSRx6@Deleted
Oct 24, 2018
Had all the features needed
I bought this for a boy who was so interested in morse code (he is only 7) - but he is practicing words already - so happy to have given this to him.
Verified purchase: YesCondition: New
by wbswarner
Nov 09, 2017
Key and Oscillator
Nice straight key on a solid base with adjustable tone oscillator. Perfect for practice and improving ear/hand skills. Nice quality. I keep it on my desk and knock out some Code daily.
Verified purchase: YesCondition: New
by vi_us70
Jun 26, 2018
Good for code practice
Works good but it is great with head phones
Verified purchase: YesCondition: New
by 7ojo3-2jtpw@Deleted
Dec 23, 2021
Can't wait to attach a transmitter. Easy to set up.
Easy to use by just adding a battery
Verified purchase: YesCondition: New