Internet pickings seem mighty slim, would appreciate links to books, articles or websites.
If there are good "how to" items that explain the design, that too. Thanks and 73s
The best reference is from Jim Brown, K9YC.
http://audiosystemsgroup.com/RFI-Ham.pdf is a well-respected and accurate reference.
Low Band DXing by John Devoldere, ON4UN has a chapter that contains information about binocular core transformers. Available from the ARRL.