Hardware modifications to Rev 1.3
(corresponds with Rev 1.2 second edition)
The alterations made from Rev 1.3 to Rev 1.4 of the FiFi SDR are described on this page.
Explanation: Although Revision 1.3 is contained in the project data, the circuit board was never manufactured. The differences between Rev 1.2 and Rev 1.3 can be completely recreated by changing components. More accurately: in our Rev 1.3, R5 was removed from the circuit and replaced by a wire link. Funkamateur on the other hand simply fitted R5 with 0 Ohm. Because of this very marginal change, Rev 1.3 and Rev 1.2 are viewed in this Wiki as identical. Rev 1.2 second edition was delivered by FUNKAMATEUR as from October 2011.
To the changes: Rev 1.4 includes comprehensive layout improvements.
- The ground separation between analog and digital earths has been completely eliminated. Just the HF ground that is separated by the transformer remains separate.
- The 3.3V supply to the OP and 'mixer' (FET switch) is now over separate tracks. In the previous layout, the track went first via Block C, then to the mixer and from there onward in the direction of the OP. There was therefore no provision for interference currents between the mixer and the following analog section.
- An additional ceramic capacitor in 0603 and a bulk capacitor (tant. size A) have been added to the mixer.
- These alterations are described in more detail in ticket:102#comment:16
- Apart from these, no other changes were made compared to Rev 1.3.
Although it is relatively easy to reverse the ground separation on existing (older) boards, alterations to the supply for the mixer and the OP are very complex. There is a high risk that tracks or the legs of ICs will be damaged. We therefore recommend that this is not attempted.
IF you do decide to take this risk, then please study the modification documentation (only in German) by Martin Brass. Many thanks to Martin at this point for his comprehensive work.