Nuts and Volts - September/October 2018

printed circuit board burns.

The code keyer must be connected, even if you don’t plan to use the Ubitx for Morse Code.

I used an on/off toggle switch for my PTT (push to talk) switch, but a standard microphone can be added if desired. There are plenty of schematics online which show how a hand microphone can be connected to a Ubitx.

The microphone, CW keyer, and speaker are connected to the Ubitx through three 3. 5 mm sockets which are included with the kit.

Building My Enclosure

As I’ve done with past projects, I fabricated my enclosure from a thin metal box which was once used as a cookie tin. I like using this type of enclosure because they’re inexpensive and plentiful, and can be found in many different shapes and sizes.

Perhaps the best feature of using this type of material is that a nice enclosure can be fabricated by using common hand tools. Learning how to build an enclosure from thin gauge metal has at times been tricky business, but over the years, I’ve acquired a few techniques that work well.

The most difficult task in fabricating an enclosure from a thin metal box is cutting the opening for the 16x2 mm LCD. I like to begin by carefully marking the spot for the LCD opening and then scoring it with a sharp edge. Once the opening is marked and scored, I drill four relief holes; one on the inside of each corner. The relief holes will stop me from cutting beyond the mark. I use a rotary tool with a cutting disc to cut the opening.

Openings for the encoder, volume control, and other parts are relatively easy to cut. I prefer to cut these types of openings with a hand drill, but some builders have been successful using a metal punch.

When laying out the enclosure, it’s best to place the openings for the power and antenna connector in the rear panel of the box. The openings for the keyer, speaker, PTT, microphone, and volume control should be placed on the front panel of the box.

Once cutting and drilling are completed, I lightly sand the box and follow that by applying a coat of automotive primer. Any primer will likely work, but I’ve found that paint will adhere to automotive primer quite well. Once the primer has dried, I paint my enclosure with a lightly textured paint which is very good at covering scratches on the metal.

The Moment of Truth

I’d built a nice enclosure and completed the Ubitx assembly. The time had now come to test my unit (Figure 10). Like many hobbyists, I’ve often used the term “smoke test” in a joking manner, but with the Ubitx audio chips overheating and exploding, that phrase didn’t seem quite as funny as it once did. It was now time to find out if the audio chip on my Ubitx was going to work.

I made one more scan of the wiring to ensure each part was correctly connected and switched on 13. 8 volts of the power.

To my satisfaction and relief, my Ubitx powered up without blowing the audio chip. As I listened, however, the audio began to degrade and show signs of distortion. After operating for a few minutes, the audio became too distorted to be understood.