CW Adapter kit

This unit has been designed to fit "in-line" with the MKARS80 to provide a CW function without modification to the MKARS80 itself.

The circuit generates CW by inserting a tone into the microphone input; to avoid harmonics of the tone appearing in the TX spectra the design incorporates two stages of bandpass filtering in the TX audio path; when used with a correctly adjusted MKARS80 unwanted spurious signals are > 40dB below the wanted carrier. In most instances these artifacts will be masked by band noise.

An identical filter is used in the receive path giving quite a narrow receive bandwidth of about 200Hz. This filter is switchable.

A break off PCB carries an Iambic keyer with memory function, the circuit and microcontroller code were designed by Wolfgang DL4YHF and are reproduced here with his permission. His website carries full information.

  • Adds a CW function to simple SSB transceivers
  • Useful for CW sending practice
  • Shaped keying
  • Built in side tone (Approx. 800Hz)
  • Adjustable side-tone level, hang time and drive level
  • Switchable narrow receive filter
  • Reverse polarity protection (fuse protected)
  • Optional Iambic memory keyer - by permission from DL4YHF
Photo showing prototype under test


CW Adapter construction manual
Version 2.0 in pdf format - Latest version for currently supplied kits.

CW Adapter construction manual in Spanish
Thanks to Jon EA2SN for the translation.

Drilling template
Printout with Adobe Acrobat reader, set paper size set to A4 and page scaling set to "none". Stick onto case as described in construction manual and use as a drilling template for the holes and cutout.

To follow (PDF)
Large type format which is easier to read than that in the manual

Old data

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NOTE: Kit version can be found on lists in all component bags

Kit Contents

The kit contains all PCB mounted components including connectors, the builder will need to provide a suitable case. The CW adapter will fit the case used by the MKARS80, the keyer however will have to be housed separately. The case is listed as an option.

How to order

This kit is now discontinued due to obsolescent components