Hi Chaps,
The KLM beam is actually 7db over a dipole in the middle of the 21MHz. band, it will take a bit of a hit at 21.9Mhz but one could try and re-tune it making it shorter is easier than making it longer!!
Those DDRR antennas need to be very very well constructed to perform efficiently because they are very short antennas. The ironmongery that one sees (loop etc.) is actually "top load" that is also used as a matching section, it doesn't have to be circular - it can be square (easier to construct). The antenna is actually the metal piece that joins the loop to the ground plane. The loop in this type of antenna does not radiate. The radiation pattern is omnidirectional and the antenna needs a good ground plane.
Cheers and beers,
Jerry.
