This might be an interesting source: http://members.ziggo.nl/d.barg/acarsweb[1].pdf
Thanks for the link.
After 5ish years of banging away at this, you get good at digging into search results and finding anything you can about ACARS message structure.
That doc is rather old and only covers VHF message structure from airline aircraft, which is one of the better formatted message types.
Where I am having the most 'trouble' is with C and L Band satellite ACARS messages. Both commercial aircraft and military aircraft transmit on those frequencies. Both have very different message structure.
