Three STL files that make the components for a microphone for a BITX40 radio: a bottom, top and button pusher on the side. Use the mic and pushbutton switch parts that are included in the Bitx40 kit from Farhan. Add a phone handset coil spring wire: this design includes a robust strain relief for this type of cable. The top and bottom snap fit together but for permanent use the design includes a hole for an M3 brass threaded insert and screw. This design uses as its inspiration the mic that Giuseppe IK8YFW designed.
73, and have fun!
I've successfully printed this in PLA and PET. For best results use the highest resolution that your printer supports.
For best results use the highest resolution that your printer supports.
Fusion360 tends to save STL objects in an edge-on orientation. When you set up the components in your slicing program, rotate each shell so that the base of each shell is flat on your printer bed. You should not have to add any supports when you slice it; there's one manually-made support in the strain relief which is a very thin wall over the 'S'-- knock this out after printing, before you thread the cable through.
Threaded Brass Inserts
The shell's two halves are fastened together using an M3 screw into a 5mm threaded brass insert. You can easily embed into the thermoplastic using a soldering iron that's just hot enough to melt it into the plastic. Google "Installing threaded inserts into 3d printed parts" to see how it's done.
This thing is designed to use the coil wire cable that's used in phone handsets. This cable contains four wires: you need one for ground (0v), one for the microphone and one for the push-to-talk button. You can leave the fourth wire unconnected, or combine it with the ground wire. The cable is pushed through the opening and then does an 'S' for strain relief. This hole is a little bit too tight and I found that with my cable I had to shave it down a bit to push it through. Use a flat-head screwdriver or similar tool to push the cable securely into the 'S' form.
The PTT switch has two leads and it can be press-fitted into place on the bottom half of the shell.
Now you can wire the PTT switch (one side to the PTT wire, the other side connect to ground), and then the microphone (one side to the mic wire--consult the instructions at hfsigs.com to tell which solder pad goes where-- and the other side to ground).
Fit the pusher into place between the guides. The button has a curve which should line up with the curve of the side of the shell. If it doesn't seem to fit well, turn it upside-down and try again. The presser part should make the switch click; it may not click if you've pressed the switch too far into the holder.
The microphone can be hot-glued into place, but use small amounts on the side of the mic--you don't want the glue to obscure the hole that you'll be talking into!
Put the two halves of the shell together, ensuring that the internal wiring isn't obstructing the pusher or getting in the way of the screw. Use an M3 screw to fasten the two parts together. And you're done!