I use 75 ohm RG6 coax for my low band receiving antenna system. RG6 is used for routing VHF and UHF TV signals so will have very low loss in the single digit MHz range. Also since it is produced in such large quantities, it is inexpensive.
The transformer uses a Fair-Rite 2873000202 binocular ferrite core. The antenna winding has 5 turns, and 2 on the coax side. This provides good impedance transformation to the 75 ohm feed line. This is the transformer design used in the commercially available BT-75 Beverage transformer.
An optional gas discharge tube is wired across the transformer. Over the years I have lost a lot of Beverage transformers if I didn’t disconnect them in the summer. The gas discharge tube helps protect the transformer from surges created by nearby lightning. Since using the tubes the last couple of years I have not lost any despite leaving them connected all summer. Knock on wood.
The K9AY Array uses two loops at right angles. By switching loops and which side the terminating resistor is connected, 4 directions are possible. Most hams in the US have them pointed NE, SE, SW and NW.
Breed’s article described a system that didn’t require separate control cables for direction control. Two relays make the switch network. Powering none, one, the other, or both of them allow selecting the 4 directions. His system used +12V, -12V and 12VAC applied to the coax to power the relays.