I've been looking into getting on the air in digital mode and wondered if anyone had tried the following setup with digilite?
Using Evariste's rpidatv in IQ mode and feeding these signals to the nyquist filters, bypassing the dsPIC and 74ACT574M chip completely. I am waiting for my digilite board to arrive, and if this method is possible, will probably not populate those two IC's and associated components, ie just build the IQ modulator part of the board.
Has anyone tried this and had success?
Sorry if this has been covered before, but I didn't find anything on the forum when I looked.
This should work, but have you considered building the DigiThin board instead? Details here: http://batc.org.uk/forum/viewforum.php?f=97
The Digithin board was designed to do what you are trying to do, but at a fixed 333KS symbol rate. There is also another variable cut-off filter and modulator designed to work with the RPi described on Page 32 of CQ-TV 251.
Hope that helps
An update: I have now tried your suggestion with the latest RPIDATV software at 1MS and 2 MS. It works well.
I feed the I and Q outputs from the RPi GPIO through 150 ohm resistors into the Nyquist filter of my DigiLite and get good results.