Stefan Burbaum wrote:
"Can anyone tell me more about this type?"

John D. Kraus, W8JK says about the Cloverleaf Antenna for FM
Broadcasting on page 429 of his 1950 edition of "Antennas":
"One method of simulating the uniform loop is illustrated in Fig.
14-38b. Here four smaller loops are connected in parallel across a
coaxial line. This arrangement is called a "cloverleaf" antenna. (P.H.
Smith, Cloverleaf Antenna for FM Broadcasting, Proc. I.R.E.,35,
1556-1563, December 1947)."

Best regards, Richard Harrison, KB5WZI