I mentioned the variable circuits because someone above had mentioned voltage reading on the remote.
The voltage drop between transformer and loco (even when measured with a voltmeter on the track, has always been a source of wonder to me. It is one reason why I only use 14-gauge wire to feed tracks. I know what the charts say is voltage drop per x feet of wire, but somehow the numbers don't work out. I'm inclined to think that there is considerable drop at some track pins and along steel rail.