I am using a single element of rectangular shape on 80 and 40
It is 33' vertical and 100' horizontal rectangle.
I have not modeled this but suspect that it performs at least as well
as 2 x 40m loops set 1/4 wave apart on 40 and has the added benefit
of working very well on 80.
perhaps a multielement version for 20mcould be made to work well on 40
No reason why it has to be short side vertical either.
In the 30's there was a popular
rectangular loop having 1/8 wave top and bottom and 3/8 wave sides.
Feed is with open wire line, trimmed to match.
Note: the plane of these loops is vertical!
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