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Radio Modifications (optional)

🚧 Under Construction 🚧

(More details and pictures will be added as time permits)

Overview

The HopeRF RFM98PW radio module has a built-in 3.3V LDO (low-dropout regulator). Since PyCubed is already supplying 3.3V (from a far more reliable regulator), it's prudent to remove the redundant and radiation-failure prone COTS 3.3V regulator on boards that need improved radiation tolerance.

  • We can get away with this since PyCubed's primary 3.3V regulator is already very low ripple and the RF module has plenty of filtering.

Instructions

  1. Remove the RFM98PW module's RF shield
    1. The RF shield is only soldered at one spot on each of the module's long sides.
    1. You'll need both hands for this. I use tweezers in my left hand and keep the soldering iron in my right hand.
    1. With your tweezers, apply upward force along the exposed edge on either of the short sides of shield.
      1. Only a slight upward force is necessary. Not too much or you could bend the shield as it comes off in the next steps.
    1. With your soldering iron, apply heat to one of the shield's solder joints while maintaining upward force with your tweezers. The lid should lift slightly on that side.
    1. Repeat the same procedure on the other side, and keep working back and forth until the lid is free.
      1. Take note of the lid orientation.
  1. With the lid removed, identify the LDO "SOT-23" package (circled below).
  1. Desolder the LDO
    1. One easy way to do this is first adding a generous amount of leaded solder to all three of the joints. This helps bring the liquidous temperature of the solder joints down.
    1. Then position yourself so you can lay your soldering iron tip along the SOT-23 side with two leads.
    1. Heat both leads up at the same time by spanning the gap with the tip of your iron. Add more solder if needed to make contact with both leads.
    1. Then quickly (but precisely) move your soldering tip to the single lead on the opposing side.
    1. If you get the timing right, the side with two leads will still be molten and the part should scoot some (or all) of the way off its pads.
      1. You may need to alternate back and forth to raise the overall temperature of the part before it easily slides off.
    1. You could also use hot air if you're experienced with the tool.
  1. Double check you didn't short any of the passive components when adding additional solder during your removal of the SOT-23.
  1. Reposition the RF shielding lid.
    1. If you don't remember the orientation, reference a top-side picture of the PyCubed mainboard.
  1. Solder the lid back in place.