Hi man,
I think the problem is related to synchronization. You have to assemble your message (i.e. the bits that modulate the IQ signal) in the following scheme:
{<Guarding bits> <Synchronization bits> <Message bits>}
The purpose of the Guarding bits is to compensate for the transient effect of the filter in the "MT Demodulate PSK.vi".
I attached an example that I created. I assembled the sync and message sequence in a way so I'm sure that the sync senquence can not be found anywhere in the message:
- Guardian bits: 00000000
- Synchronization bits: 11100111
- Message bits: 01010101010... (128 bits).
I recommend studying the example "MT PSK Transceiver (One Shot).vi" which you can find in the Example Finder.
Regards,
Norbert