Pebble HF – part 2

Building The Kit !

Okay, I cheated a little; instead of clearing my worktable, I moved a few tools downstairs and built the kit on the kitchen table.

The newspaper will protect the table surface from solder.

I used the Raspberry Pi to view the assembly instructions, located here. I recommend using this document rather than the YouTube video, the information there is fresher and reflects things recently learned in development. One of the inductors should be wound with 9 turns rather than 10 for better efficiency, and there are other useful tips as well.

The ISP header is the first thing to solder; next comes winding and soldering the two toroid inductors.

Toroid inductors in place. Just in front of them, note the tiny potentiometer. We will have more to say about that, later.

The DC power jack came with the kit; the 5.5 x 2.1 plug is user-supplied. I foresaw the need for a power cord when the radio is completed.

Pro tip: before soldering the power jack, bend the tabs flat to the pc board, the instructions note that there is a chance of contact with the LCD board.

The BS170 transistors, the diode, and the BNC jack are installed in this view.

The diode is a 1N4756 Zener diode which provides overvoltage protection for the BS170 final amplifier transistors, a very nice design refinement!

The rest of the components are installed on this side. The assembly is finished.

I needed to slightly bend the mounting tabs of the encoder to get it into the board; everything else fit the holes almost perfectly.

Okay, it’s all together; visually checked all the solder joints (for the 2nd or 3rd time, made a power cord, it’s time for the final, and most crucial, step;

THE SMOKE TEST !

The first time powering it up scared me; the LCD display lighted up, but the display was blank! Unplug! Quickly! Then I remembered the LCD contrast setting. (I think I have had this scare before, now that I think about it.)

After trying a few different screwdriver bits I settled on a #1 Philips to adjust the tiny potentiometer that I pointed out above, then powered it up again.