Use a scope and see the level of the receiver output. Should be rect pulses of almost 5 volt high. No matter if it is noise pulses or data. If you see this then you are on good road. No schmitt trigger is needed. All necessary electronics are within the receiver module.

Try this:

On the Txer send with serout or serout2 the array $55,$55,$55,$AA,$55

On the Rxer wait with the serin for a $AA and get the next byte. In our case this is $55.

I am sure if you have electrically everything by the book, you will get that byte received OK.

On the example if you check the bytes you will see that there is no continues
train of 1's or 0's. So no DC bias is created internally in the Rxer. That's the idea. Please do a search on the topic, it is cover fully here on this forum and on the mailing list archives of http://list.picbasic.com/cgi-bin/board-search.cgi

Ioannis