Recommend 14 AWG insulated wire. Home Depot Southwire 500 ft roll 14 gauge Black Stranded CU THHN wire hung as an inverted L, inverted V, etc. And trim for minimum SWR on your desired portion of the 160 meter band and you will have a multi-band antenna that performs well on 160 meter, 80 meter, 40 meter and 20 meter bands. I have two of these identical transformers in use with inverted L antenna wires.
I routinely talk with stations in Europe, Ukraine, Russia, etc. DIRECTIONS FOR USE: Connect 260 feet for 160 meters (or 130 feet for 80 meters) of 14 gauge insulated wire in inverted L or inverted V configuration. Connect Ground terminal on transformer to Ground Rod ideally 8 foot ground rod approximately 8 feet below transformer with heavy duty ground wire. Connect 50 ohm coax recommend high quality low loss cable, eg.RG 213, DXE 400 max, LMR400, or equivalent to transformer and shack output ie. Using your antenna analyzer trim far end length to achieve SWR minimum at desired frequency or 1.850 Mhz (or 3.7 Mhz for 80 meters). The item "End Fed Half Wave EFHW 64-1 Transformer 160/80/40/20 M HIGH POWER Triple Core" is in sale since Tuesday, September 14, 2021. This item is in the category "Consumer Electronics\Radio Communication\Antennas\Ham, Amateur Radio Antennas". The seller is "mooneypilot" and is located in Warren, Vermont. This item can be shipped worldwide.