Hi,

The synchronization is for the microcontroller connected to the receiver.
The duration of the synchronization pulse depends from the used baud rate.

Here is the duration of a frame at 1200 baud.

(Click to enlarge the picture).

Make sure you use 8 data bits, no parity, one stop bit.
Must be INVERTED. (See PicBasic manual).

Best regards,

Luciano