For those assembling the SBMS Pcom 23 Ghz mod "Mixer Board"
kits, also called the "3 GHz U/D Converter", there is a
polarity problem with the PIN Diodes included. They have
opposite pinout polarity compared to the way the board was
laid out. For these three-legged diodes marked "E1", the
anode side is the side with two legs. This was discovered by
N6IZW and K6QPV in checking out the first assembled kit in
If you observe the board with the mixer component at the top,
the board labels for D1 and D2 near the bottom left corner
show the two-legged side of each diode would face the left
side of the board. For the kit diodes provided, they should be
installed with their two-legged sides to the right, instead.
This can be done if you remove the green "resist" covering
the sections of the pads, that would otherwise prevent
contact of the three diode pins with the pads. Just imagine
you rotate each diode 180 degrees from its original orientation
and note where you need to expose the underlaying metal pads
to make contact with all three legs in the new position.