MFJ Enterprises Original MFJ-557 Deluxe Morse Code Practice Oscillator Straight Key w/Volume Control
Key features
- •The MFJ-557 Deluxe Morse Code Practice Oscillator runs on a 9 volt battery (not included) or 110 VAC. It measures 8 1/2 x 2 1/4 x 3 3/4 inches. It comes with MFJs famous one year No Matter What warranty.
MFJ Enterprises Original MFJ-557 Deluxe Morse Code Practice Oscillator Straight Key w/Volume Control
List Price: $105.85$95.27DEALYou Save: $10.58 (10%)
Free shippingFree Returns – 30 daysFree Order CancellationSecure Payment2–3 Days DeliveryGet It June 23, 2026In Stock (1)No marketing spamNo account requiredFulfilment by FedEx / Amazon / UPS / ShipwirePayPal / Card Buyer Protection
Customer Reviews
Reviews sourced from verified Amazon purchasers4.3
out of 5
Based on 10 reviews
5★
70%
4★
30%
3★
0%
2★
0%
1★
0%
Exactly What do You expect from a Training Tool?
Remnant•September 15, 2017
I've seen some of the other reviews for this product, and I frankly wonder if some of the negative reviewers suffer from OCD.
This is a training tool, and not designed as a "true" straight key.
Yes, it doesn't have adjustments for left-to-right alignment, but if the contacts are making contact, then who cares? If they are really
far off you could bend the ears holding the paddle to make them align better. (Whatever happened to HAM's modifying their equipment?)
As far as the two adjustments that are critical, gap and pressure, you can tune this key to whatever you like. (Think light and light!!!)
My initial irk with the unit was that even under battery power, the frequency would shift, which was kinda annoying to a former audio
engineer. Then, listening to the radio and trying to decode CW, I found that what you heard would also shift, so now I count that as a
bonus, a sort of "this is what you could expect to hear" kinda thing.
Once I learn the code, I plan on using this product in real-time until I can find a vintage straight key
73's!
This is a training tool, and not designed as a "true" straight key.
Yes, it doesn't have adjustments for left-to-right alignment, but if the contacts are making contact, then who cares? If they are really
far off you could bend the ears holding the paddle to make them align better. (Whatever happened to HAM's modifying their equipment?)
As far as the two adjustments that are critical, gap and pressure, you can tune this key to whatever you like. (Think light and light!!!)
My initial irk with the unit was that even under battery power, the frequency would shift, which was kinda annoying to a former audio
engineer. Then, listening to the radio and trying to decode CW, I found that what you heard would also shift, so now I count that as a
bonus, a sort of "this is what you could expect to hear" kinda thing.
Once I learn the code, I plan on using this product in real-time until I can find a vintage straight key
73's!
Great educational gadget for practicing Morse Code
jimmy•July 2, 2017
Well-made with a good, solid feel and reliable operation. The volume and pitch of the tone are adjustable. The key works as promised.
A tip. The headphone jack is monaural. I'd be willing to bet that most headphones sold nowadays are stereo. In the latter case, only one earpiece will sound. A mono-stereo adapter will bring sound to the other ear as well.
A tip. The headphone jack is monaural. I'd be willing to bet that most headphones sold nowadays are stereo. In the latter case, only one earpiece will sound. A mono-stereo adapter will bring sound to the other ear as well.
Excellent Practice Keyer
Amazon Customer•June 13, 2016
It feels like I am on the net coding. I have gone from just knowing the Morse code to quality practice. I like the head phone jack because my wife gets irritated if I practice without headphones in the house. Since this purchase I have purchased a Straight key and a Bug. I am almost to the point where I should be able to go on the net and CW.
Awesmoe buy for CW Morse Code Newbies.
Denver Dave•April 21, 2016
Very good quality, durability and ruggedness for the money. Oscillator connects to my headphones without any issue.
This is a GREAT product for brushing up and learning Morse Code (CW) for beginners.
The open posts can allow the operator to disconnect from the mounted straight key and connect it directly to a computer's COM port via USB connections so that the keyer could be used on computer aided tutorial programs. Or the oscillator can be connected to a higher quality straight key.
The only minor draw back is that this particular straight key does not have an adjustable pivot for aligning the contact.
This is a GREAT product for brushing up and learning Morse Code (CW) for beginners.
The open posts can allow the operator to disconnect from the mounted straight key and connect it directly to a computer's COM port via USB connections so that the keyer could be used on computer aided tutorial programs. Or the oscillator can be connected to a higher quality straight key.
The only minor draw back is that this particular straight key does not have an adjustable pivot for aligning the contact.
Works with 12 year olds!
Melanie A. Reap•February 19, 2016
Arrived promptly and was easy to set up. I use this to teach CW to fifth graders and it has withstood their use. Even considering getting a second one.
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