Just contacted the author of 551conv, the amiga program that writes atr disks in a standard amiga 5.25 drive, for use on the real atari 1050 drive.
It works, no extra cable needed, it writes straight to the standard amiga drive...
A few things to consider...
-You need to write on floppy´s that were NOT used on an atari 1050 drive before because the head of an amiga drive is smaller, so the amiga head is not capable of erasing, overwriting all magnatized material on the floppy thus creating errors for the real 1050 drive to read.
-You need atr files of +- 90kb or +- 130kb to match the size of real 1050 disks
Many thanks to Achim Haertel, the author of 551conv to explain me everything after all these years. I hope this is info is useful to others