QLF Filter Assembly Procedure

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You are about to construct one of only a few existing QLF filters in the world. Never before has so much technology been applied to support something as simple and old as Morse Code. I started on this digital code stuff back when I was a Novice. My first project was a digital Morse Code Clock which was published in QST, July 1979. That used discrete TTL logic. A lot has happened since then in the way of microprocessors. A lot has happened to me to. I went to the U of Fla to study engineering, and then on to IBM. Today I am still there, working on firmware for the RS/6000 Power-PC based servers. I have Ham radio to thank for my interest in electronics and a foundation for a life long career. Someday this project may show up in the pages of QST. Let me know what you think.

I recommend that you construct the circuit on a prototype board initially, in order to become familiar with the circuit. In this way, it will be easier to plan how you want to package the device for your application.

The photo below shows my assembly on two Radio Shack prototype boards. The microprocessor is on the upper left. You can also see the crystal and reset circuit. Next to it is the 74LS240. Then the 6 LEDs followed by the speaker driver transistor. On the bottom half is the rig keying circuit and the temporary LED to see it working. When you construct the circuit in it's final package, you may want to use a metal or shielded box to help reduce RFI. Be sure you use a good source of 5V, since the logic requires TTL voltages. You may want to add connectors and a permanent speaker. Plan how you want to display the LEDs. You may want to add switches to control the power or the speaker.

Take your time and enjoy the project. I have constructed lots of kits over the years, and by far, the most enjoyable part is the construction and the pride of doing the best possible job.

If you have any comments, please drop me a note. You can find me at

Hope you like the project.