Redback

A capacitor might help maintain the receiver voltage during a short period when a high servo load dragged down the battery voltage, however it would require a diode in the circuit to stop the capacitor charge leaking back to the servos.

Bringing the diode into the circuit would also have the effect of reducing the receiver voltage by the forward voltage drop across the diode.

The way it would work is that normally the receiver would run off the battery, and the capacitor would charge to the supply voltage minus the drop across the diode.

If the supply dropped enough the diode would switch off, and the Rx would get power from the capacitor. However, as the charge drains out of the capacitor the voltage across it would fall, and would continue to do so until the supply voltage came back up again (or until it ran out of charge).

The key issue here is the size of the capacitor, and this in turn would be dictated by how long the supply voltage is likely to be below that required by the receiver. Haven't got around to doing the calculations, but I suspect that a rather large capacitor would be required to give any meaningful protection.

Terry