The DELTA-20HP is a full wave loop designed to operate on 20m (14MHz), 15m (21MHz) and 10m (28MHz) without an ATU and other bands with an ATU. There is a 4:1 balun at the feedpoint enabling it to be fed directly with 50ohm coax - RG-213 or Mini 8 is probably the best but other variations of coax may be used so long as they are of a 50ohm impedance.
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