The Radio Source TheMATCHBOX Broadband Matching Transformer is a multi-tap transmission-line transformer designed to raise the inherently low feed-point impedance of electrically short end-fed antennas to a value suitable for direct connection to 50-ohm coaxial cable. Unlike conventional transformers that provide optimal performance primarily above 1 MHz, TheMATCHBOX delivers efficient operation down to 100 kHz using a manganese-zinc (MnZn) toroid core, minimizing loss while maintaining a low standing wave ratio.

Because the feed-point impedance of electrically short end-fed antennas is influenced by antenna length, ground conductivity, and ground system quality, TheMATCHBOX is field-configurable with eight impedance transformation ratios. This flexibility allows it to match antennas with feed-point impedances ranging from 3 to 37 ohms to a standard 50-ohm coaxial feed line.

Designed for permanent outdoor installation, TheMATCHBOX is housed in a rugged, weatherproof aluminum enclosure that mounts directly at the antenna feed point. Integrated top and bottom mounting flanges allow for secure attachment to a wide variety of support structures, providing a durable and reliable solution for LF and MF antenna systems

Additional Features & Specifications:

• Power Rating: 300 Watts continuous.

• Frequency Range: 100 kHz to 1.7 MHz.

• Construction: Multi-filar winding on a medium-permeability MnZn toroid core.

• Impedance Selection: Internal jumper/screw terminals.

• Accessories: Mounting straps; ground jumper/clamp.

• Connectors: Coax: SO-239; Ground: Internal stud.

• Dimensions: (HWD) 6.25 x 4.0 x 3.25 in. / Height with flanges 7.5 in.

• Cover Attachment: Four screws.

• Weight: 2.5 lbs.

• NEMA Rating: 2, 3, 4, 4X, 6, 12, and 13.

• IP Rating: IP68.