It is possible depending on speed, cable, interference and drive and input electronics to obtain more range than what the standard supports. But to be on the safe side, choose the right tool for the job to have repeatable results.

So, even if the 50m that Sayzer succeeded in are impressive it could be even longer for a more powerfull drive circuit and a more sophisticated input front-end. But for what reason when you have at hand the most reliable and cheap RS-485 chip, SN75176 and of course all other clones that work similar, better or faster? It is made for the long range network and it does that in an easy and perfect manner.

Used it alot and had no problem either in short or long distances. In fact I like it so that even for very short distances I am considering to use it because of the multi drop features.

Ioannis