In terms of voltage drop over thin wire with nmea, it took me a day to diagnose this: the ais
signal from the vhf
split to 2 plotters, one at the end of signal wire that was too thin, combined to create an nmea signal that was less than 1v. Too low for one of the chart plotters to read. I ended up using a cheap
multiplexer as a signal booster.
Not sure if the voltage drop came from the wire, the other chart plotter internal resistance, or a weak output from the vhf.