The Natural Philosopher wrote:

I still think Andy should amaze us by calculating the correct capacitor
to put on the end to make it a zero reactive load..

Lets see. 2 ohms at 125 KHZ..

I make that 0.6uF.

So sticking a 0,6uF capacitor across the far end of the cable should
make it all soring to brightness again.

?

Less than that, I reckon. What you need to do as to add C to make the
Zo of the transmission line equal to the load resistance. As any fule
no, Zo = sqrt(L/C), so C = L / Zo^2. In this case Zo needs to be 3.6
ohms (12 V /3.3 A), so C = 0.9E-6/3.6^2, which is about 70 nF/m - so a
220 nF cap should be about right for the 3m run. Might be worth a try,
although, as others have pointed out, the 'transformer' could object to
the reactive load presented at higher harmonic frequencies by such an
arrangement.

--
Andy