Radionerds.com has an immense amount of US Military Radio Related Documentation that is in Public Domain. The link is in our 'Web Pages' section of the 'References' page, shown here: The R-390A 'Web Pages' section <https://www.r-390a.net/faq-refs.htm#Web%20Pages>. Here's a link to: Radio Nerds <https://www.radionerds.com/>. Regards, Larry