hi Bane,
no problem.
Than I connected it to the 150 coil of wire
this wire is also CAT5e right?
so 90% of the time you have a bad cable it's a problem with the crimping on the RJ45 connectors.
ideally i'd lent you a cable tester but in the absence of one of those,
get a multimeter and test the connectivity of each strand end to end.
also test for shorts between pins.
but hey, it's possible that your wiring is fine and that it is your interfaces that aren't delivering the required power.
i've run a lot of long CAT5e cable in the past but usually it's plugged into commercial equipment that conforms to the RFCs so it is possible you are experiencing something different from what i have seen.
your initial question about an ethernet amplifier:
it's not really possible to build one without a *lot* of effort but any ethernet switch will regenerate the signal.
if you have an old switch sitting around try using that between your computer and the long network cable.
dunk.