Hi Chris,
My understanding is that David (G4RVH) has built the board from scratch and therefore some of the components are what were available.
- The electrolytic capacitors are across the relay coils. Pre-built boards have 1uF SMDs.
- A diode has been added across each relay coil to reduce the back EMF. This is not strictly necessary and using a diode without the capacitor could cause a problem due to rectified RF energising the relays.
- A series resistor and LED have been added in parallel with the relay coil for test purposes, so that there is an indication of which relays are energised.
Hopefully, that covers your question.
73, Dave (G8PTN)
