Wayne Wright edited this page Mar 18, 2018 · 12 revisions

MK1101 and MK1102

The W5XD Multi-Keyer model MK-1100 has been out of production for many years, but several of its features are still not obsolete. These include:
  • Seamless integration with WriteLog.
  • Optically isolated Left and Right Morse CW and PTT outputs.
  • Footswitch input.
  • Reliable front panel Morse speed and Left/Right overides.
  • One COM port does both CW and rig control.

Aside from the fact you can't get one, the MK-1100's biggest issue in the modern ham shack is its requirement for low latency on the PC COM port modem control lines. PC's with a motherboard COM port can be counted on to have adequate specifications for the MK-1100, but USB to Serial dongles generally do not.

Here are redesigns that resolve both those issues.


The MK1101 (back panel, before application of dry transfers) front left, MK1102 (front panel) back left, and original MK1100, right.

These updated devices duplicate the functionality of the MK-1100, plug into your PC using USB, and can be built in quantity one using parts readily available in 2018.



With minor exceptions detailed below, they are software compatible with all versions of WriteLog back to version 10.10, and pin-out compatible with the original MK-1100. The new parts are smaller, so you get a smaller footprint at your operating position. A complete parts list is provided below, including commercially manufactured enclosures, along with drilling templates for them. Printed circuit layouts are published here in the format supported by http://expresspcb.com. The necessary firmware is also published here.

This design has two variations that can be built. The MK-1101 has the essential features for SO2R in the smallest package. The MK-1102 adds the full implementation of all features and connectors of the original MK-1100. WriteLog accesses any of the three with its same MK-1100 setting. The features in the MK-1102 omitted from the smaller MK-1101 device are:

  • 25 pin D LPT outputs for both Left and Right radios with TTL levels for 4-bit band decoding, L/R radio indicator, CW and PTT.
  • Stereo audio switching for Left and Right receivers to Headphones.

The MK-1101 and MK-1102 designs share the main printed circuit board implementing the features they have in common. The MK-1102 adds a second circuit board (called "Aux" on its silkscreen) with the LPT ports and headphone switching. Each design fits into a commercially manufactured Bud enclosure, the MK-1101 into a smaller model of the same series. The second board is connected to the main board by 8 conductor cable using RS-485 signalling, and requires a 12VDC supply. This division adds yet a third packaging option (not further documented here) to separate the two boards over a large distance should you design your own two enclosures. The MK-1102 design detailed here fits both boards into one enclosure.

Differences from MK-1100

While the MK-1101 and MK-1102 are highly compatible with the original MK-1100, there are a few design details that differ.
  • micro-USB connector to PC instead of RS-232 9 pin D.
  • sidetone on audio sounder instead of coupling into headphone switching.
  • manual speed and L/R switch on front panel instead of on remote cable.
  • the MK-1101 is powered through USB. MK-1102 requires 7.5-12V DC, positive on center pin. MK-1100 required external 7.5-25V DC, either polarity on center pin. The power jacks mate with the same connectors.
  • The self test built into the MK-1101 and MK-1102 requires a different fixture than the MK-1100. A PCB layout for a MK-1101 and MK-1102 test fixture is published here.
  • The MK-1102 fits into a much smaller space than the MK-1100, and the MK-1101 is smaller still.

Cabling and Operation

The MK-1101 and MK-1102 jacks have the same pinout as the original MK-1100, and, except for substituting the micro-USB for the 9 pin D, and the requirement for positive polarity on the 12VDC center pin, the instructions for connecting the MK-1101 and MK-1102 are identical to the instructions for the original model.


Parts lists and complete instructions for building both the MK-1101 and MK-1102.


MK-1101 and MK-1102 main board

MK-1102 aux board

Test Fixture

If you're going to build more than one of these, this Test Fixture simplifies the checkout.
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