What is the transmitter distribution efficiency supposed to be? The tooltip on the transmitter says 3, but as far as I can tell the effect is 2.

For example, an arc furnace with a 1.5 efficiency beacon that holds a single speed 2 module (30% speed and 60% power) gets +45% speed and +90% power. With a transmitter instead of a beacon, it gets +60% speed and +120% power. With an efficiency of 3 as the tooltip says I would have expected +90% speed and +180% power. Same deal for efficiency modules - twice the effect not three times.

Do I not understand how transmission efficiency is calculated, is the tooltip wrong, is the building being rebalanced by another mod, or what is going on here?

it is intended, you need 2 transmitters for full efficiency

I see, thanks a lot for explaining it. As a suggestion, perhaps the tooltip or research could be made a bit more descriptive, because it is not immediately intuitive that two buildings are necessary to get the stated effect. Currently, the transmitter tooltip text is just a bit of flavor stating "good things come in small packages".