Opening the Apollo Pre-Modulation Processor (Patreon)

We just opened the PMP, or premodulation processor box. It's the box that comes after (or before, depending how you look at it) the transponder. It is described by Collins as the heart of the system. It is in charge of modulating and demodulating all the sub-carriers. It's of pretty spectacular construction.

In and out of this thing comes the voice. The digital data downstream goes directly into this box. The data upstream is more complicated, the PMP extracts the first layer of FM sub-carrier, but it takes yet another box to extract the PSK data and decode it.

Mike is already hard at work trying to figure out what all the pins do, so we can try to connect it to our system.

Marc