CW Messenger: Prototype Testing

I built part of the CW Messenger on breadboard to further test the CW Messenger software. Here is a video of it “sending” message #1 (note that I haven’t modified the author’s original stored messages yet).

Notice anything in the video? The software is working as expected, but the buzzer is only clicking. That’s strange!

My Buzzer Doesn’t Buzz

My buzzer (datasheet) turned out to be more of a clicker here. I thought a buzzer would buzz. Duh!

Reading the datasheet more closely, I see it notes the buzzer is “externally driven”. It shows a circuit where a square wave is being applied (through a transistor). Interestingly, the product page at Mouser notes the buzzer’s frequency as 2.73 kHz. I pick this buzzer explicitly for that. From the datasheet, it appears that this is just the frequency they used to specify current consumption. It’s not any particular characteristic of the buzzer. The buzzer will actually “buzz” at whatever frequency is applied to it.

I seem to learn something new every day. I’ll need to order another buzzer!

Driving the S-Pixie

I mocked up a bit more of the CW Messenger and connected it to my S-Pixie. Here is it “sending” the author’s message #3. Note that the buzzing is coming from the S-Pixie. Its buzzer actually buzzes!

I think I’m ready to start laying out the protoboard. First though I thought I’d make things complete and test out the CW Messenger keying the S-Pixie (PCB build) “transmitting” to the S-Pixie (breadboard build). Here’s a picture of the set up.

No need for another video. I works the same as before.

The S-Pixie PCB build is connected to the breadboard build through a 30 dB attenuator. It works pretty much just as well with the PCB “transmitting” into a dummy load and just a random wire (or nothing at all) connected to the breadboard build antenna BNC. I’ll have to try it out the other way around to see if there is any improvement in the noise level.

I’ll need to test the output power of the S-Pixie during my transmission testing. The transmission power of the S-Pixie is specified as 1.2 W though the output amplifier transistor (8050 datasheet) is rated at 2 W. The 30 dB attenuator I used above is rated at 1 W so I’ll want to verify the actual S-Pixie power before doing much more testing like this.

That’s enough testing. It’s time to move on to building the CW Messenger for real.


I give updates on my projects in the r/HamRadioHomebrew community on Reddit. I make those updates mostly in real-time and use them later as the basis for my documentation here. As such, my posts here are similar but usually have more detail than my Reddit posts.