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Your cart is empty. Deluxe Morse Code Practice Oscillator, Has Volume Control, Tone Control and a Built In Speaker.
Built In Straight Key Can be Removed for Use On A Transmitter. Requires 1 Optional 9V Battery, also can be used with an Optional AC adapter too! ( 9v Battery or AC adapter not included).
Will
2025-08-13 15:58:06
I bought this to help learn Morse code. Very sturdy build,arrived in perfect shape and works great. Would recommend
Rob Not
2025-07-23 14:18:49
This is a solidly-built straight CW keyer. I've "book-learned" morse code, but keying morse is another thing. I practice using this with a morse code app that reads and decodes sound signals. Then I can tell whether I'm keying the letters and numbers correctly, and whether I'm pausing between letters and words correctly at different speeds. It works fine with either a 9V battery or a 12V DC adapter. The sound module is definitely analog, with some variation in pitch ("chirp"), but it's not a problem for practice. If connected to a radio, you must disconnect the key from the sound module hence it will not be used at all, so the chirp from the sound generation module isn't an issue. The tension and throw adjustments are a tried-and-true design that work well for light touch activation and release.
Narf
2025-07-19 17:46:03
I have learned a lot of CW in the short time that I've had the MFJ-557. I think being able to actually hear my morse as I pound it out on this has really helped me start taking off in my CW journey. That being said, I was pretty horified when I opened up the cover to put a 9 volt in it. Holy moly, it's an absolute mess of wires, hot glue, and tape. The speaker is held on by tape to the plastic housing... just so cheap lol. I mean, I paid 90 bucks for this, and to be honest I don't even think I would expect that kind of internal build quality from something even $50 bucks. Overall, I am enjoying it though.
x6729c
2025-07-02 10:47:44
First thing I did was get rid of the baseplate and hand key which is 4 screws. I then hooked it up to my vibroplex bug and used it to practice and works excellent and has good tone and volume control and small. Nobody else make code oscillators these days but I need one to practice using mechanical vibroplex bug as I do not like electronic keyers. The price is to high though but since nobody else make these they can charge what they want. They should sell just the oscillator box by itself and the user hooks up their favorite key.
pmd1973
2025-05-12 14:37:15
I was disappointed to discover this key was non functional. I checked the connections from the key to the practice oscillator and made sure the battery was good with a meter. I also attempted to check for audio using the ear phone jack as well... No dice. The quality of the key itself is usable, but the contacts were not very well aligned. There is no adjustment to bring the contacts back into alignment, just a tension and gap adjustment.
jimmy
2025-05-10 15:56:48
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.
Nathan K.
2025-04-25 10:36:05
So the product works, but I feel for 80 something bucks, it was made very cheap, and was poorly put together. The metal arm was badly bent / warped and had to be fixed. When opening the black box, to place the 9volt battery in, the speaker and electrical stuff was rattling loose inside the box... There is nothing that keeps the battery from rattling around. The speaker is only being held together by tape, and the circuit board is being held by hot glue and the knob control. I ended up doing some soldering and fixing what I can inside. Also replaced the very cheap speaker with something much better, as the speaker. Yes the tool works, and is OK for beginners, but for the price, I think it's a bit too high for the quality you receive.Maybe they'll design something better in the future.
John C
2025-03-10 17:42:24
I miss the days when someone could walk in to any Radio Shack and buy a solid brass key for $6.95, BUT those days are gone :-( and I have to get used to it. This is a nice little straight key on a solid, heavy base, and I like having the oscillator to practice CW in the car (yes, I'm that nuts) when I'm not making actual contacts. About that, it's quite easy to modify this unit to quickly switch between practice and sending, mine has a 1/4" jack in the side for the transmitter, the kind that breaks tip connection when you plug in but if you've read this far you know what to do :-) Sorry MFJ, guess my warranty is void. And about MFJ, they are one of the best known and highest quality manufacturers in the business, well known and loved by many in the amateur radio world. Check out their guarantee.Before I sign off, one important warning: And I ain't pointing fingers, I'm just sayin. If you're planning to buy radio equipment, or ANY equipment for that matter, through Amazon or eBay or craigslist or a classified ad in the newspaper, do yourself a favor and view or download a catalog from the manufacturer (you can download the entire MFJ catalog from their website) or a reliable reseller (GigaParts, Ham City, etc.) to ensure that the price is in the right ballpark and the warranties etc are intact. Cause somebody might, hypothetically, buy this unit for $50 and try to sell it to you for $150. I'm just sayin. Cheers!
FRANCISCO MAYAGOITIA
2025-02-01 17:58:39
Cumplió las expectativas. Funciona bien
sab
2024-12-25 17:25:39
Easy to use and a perfect tool for Morse code sound; it will Help you after you have learned all the Alphabet Morse chart then you practice with that instrument for Morse code sounds.
dale heinzig
2024-12-12 10:56:30
mechanically it's good. works as it should. there was a plastic cover on the item itself that was broken. only cosmetic. doesn't hinder the actual function.. tried to contact seller, he just answered that he was glad I was happy.. I think there is a communication breakdown somewhere..
safe
2024-12-03 20:03:13
The key took a while to arrive, but came well packed and once I put a battery in, instantly ready to go. The key handle was quite sharp around the key handle edges and uncomfortable and I had to file down those sharp plastic edges. Even then the flatness of the key is uncomfortable for me. The key appears to have acceptable tolerances, although taking a while to find the right tolerances for me personally. I definitely like it over all the other cheap rubbish on the market. It’s ok if you just want to practice on a budget. Otherwise buy a real key you will use in transmission and get a feed back system, or simply connect any key to this unit for an instant Morse practice. All in all, not bad, but I feel a little expensive, but I suppose get a better quality than most of the crap practice keys out there. This is the real thing to practice with though!
Kimsk
2024-11-29 19:58:55
The headphone input has failed, and if I try to insert my headphone jack into the input it goes straight through. The item is still usable, but I can't use headphones. I will try to fix, or return for a new one.
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