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MFJ MFJ-403 SKU: ZMF-403


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CW Travel Keyer 

This new MFJ Travel Keyer is a full-featured CW keyer (no paddles). Its ultra-compact size is perfect for traveling or for home use with QRP or "big" rigs. Throw it in your briefcase alone with your MFJ QRPCub or other favorite rig on your next trip. 

Send Beautiful CW with no effort 

Self-completing dots and dashes and dot-dash memory is very forgiving of timing mistakes. It lets you perfectly form dots, dashes and spaces effortlessly for accurate professional sounding CW. 

Adjust Speed on the Fly 

A thumb wheel control lets you adjust speed on-the-fly 3 to 65 words-per-minute. 

Adjustable Weight 

Dot-dash weight is adjustable 25% to 75% to make your signal distinctive in a pile-up. It also lets you compensate for transmitter turn-on delay. 

Sidetone with Speaker 

A built-in sidetone with LM386 audio amplifier, speaker and volume control makes monitoring your sending easy. Sidetone pitch is adjustable 300 to 1000 Hz. 

Keyer Modes 

You can select a keyer mode to suit you -- Iambic mode A or B, fully automatic or semi-auto "bug" mode. 

RF Proof 

Effective RF proofing lets your MFJ-403 work in any strong RF environment. 

Positive Keying Output 

It's positive keying FET output lets you key nearly all modern transceivers and transmitters. 

Battery Saver 

You'll think your battery will last forever -- your keyer goes to sleep during periods of inactivity. Uses a readily available 9-volt battery. 


  • Voltage requirements: Internal 9-volt transistor battery
  • Keyer speed: Typically 5 to 60 WPM
  • Sidetone level: 50-mW max., adjustable internal trimpot
  • Sidetone frequency: 727 Hz default, adjustable 300 to 1000 Hz
  • Keying limits: Positive keying. 50 volts at 100 mA max
  • CW generation: Iambic A or B, Automatic or Semi-automatic
  • Memory: Dot Dash memory
  • Weight: 50% default, adjustable 25 to 75 percent
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