Rockmite Log 22/11/21 Looking at the transmitter output Also, Unschooling Thoughts

I’m really enjoying WA4EFS’ website. The projects look like they were a ton of work, but the author melds all the various topics, analog, digital, and RF together so seamlessly, it’s easy to believe that they should be effortless works of love. In one of his videos he looks at the quality of the output radio wave from one of his transmitter project. It inspired me to do the same for the Rockmite.

I set up a dummy load: for the transmitter: two 1 Watt 100 ohm resistors. The pair, in parallel, gave me a total resistive load of 50 ohms, (=nominally speaking; (49.2 ohms once all the tolerances came into play).:

I attached the dummy load to the Rockmite, then attached the scope probe across the resistors. I realized I might have an issue since I could only cause transmit by sending either a dot or dash with the keyer. I used the dash speed control to slow down dashes as much as I could, and tried the first experiment: sending a dash.

The scope captured the waveform, and held it even after the dash was complete! Now, I was free to inspect the amplitude and frequency at my leisure. This was so cool! I’ve never appreciated digital scopes till just then! The stored waveform may have made them OK in my mind.

Looking at the output wave and calculating the RF power it respresents across a 50 ohm load, I arrive at a total output power of 250 mW: half of what I thought I had.

So, what’s next? See the little jaggies all over the waveform? They might be real. When the key turns on and off, rather than a sine wave, it’s a step function followed/proceeded by a sine wave. That requires a higher frequencies. There’s a frequency analyzer laying around the maker space, and it might be time to learn how to use it.

Here's the bench setup, notice the dummy load hooke up to the Rockmite's antenna port:

In other notes, my unschooling game is changing back to a more informal show everything to the kids kind of methodology. The oldest kid, 11 year-old Daize found a color LCD display months ago. I put doing anything with it on the back burner because, to me, it seemed complicated. Reading through WA4EFS'' website, it seems like it's actually kinda simple (SWR meter project).

When I found the project, I called the kid in right away and we reviewed the code. While reviewing the project, we wound up looking at source code that literally defined a picture bit-by-bit. I called in 9 year-old Mota to review this material since he'd been working on RGB hex color codes in the last few months.

All in all, things are starting to feel better in the unschooling direction for me, (isn't it intersting that I don't ever talk aobut my worries ahead of time? I'll have to work on that.) I'm sharing more. The kids can take it or leave it (as they should), and things are moving along more naturally.

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