Should the unit be turned off when starting up the aircraft?

When using aircraft power it is always a good idea to keep any avionics off during startup. Since the aircraft has only two sources of power, the battery and the alternator, engine starting causes the battery to contribute considerable amperage to the starter which reduces it’s output voltage below that of acceptable levels for most avionics. While older, tube-style avionics are not as affected, newer processor-based avionics, such as XRX, may not deal well with this situation, even though most avionics devices turned on during this time period should simply reset itself. A potential power surge does pose some risk, however this is not very likely since the output voltage on most alternators are protected from such.