Hi All,
I recall that there were two QST articles from 2007 that address this subject.
One is from March, 2007 and the article is entitled "Compact 40 meter HF Loop for Your Recreational Vehicle", on page # 41.
The other is from May, 2007 entitled "A Super Duper Five Band Portable Antenna", on page # 34.
Hope this helps,
Alan...KI6HPO