The United Microsystems BT-75/BOG Beverage-on-Ground (BOG) Antenna Transformers are specifically designed for Beverage-on-Ground receive antennas and is based on the proven BT-75 transformer used with elevated Beverage antennas. Because BOG antennas are installed directly on or just above the ground, they require no supports and can be significantly shorter than traditional Beverage antennas, making them a practical option where space is limited.

BOG antennas typically exhibit lower impedance than elevated Beverage antennas. The BT-75/BOG is optimized to provide proper impedance matching between the antenna and 75-ohm RG-6 coaxial cable, improving performance compared to standard Beverage transformers. For correct operation, the far end of the antenna must be terminated with a 250 to 300-ohm resistive load. The United Microsystems RXT-270 termination resistor is recommended.

Properly installed Beverage antennas are low-noise, receive-only antennas that provide excellent rejection of signals and noise from the undesired direction. Due to the lower velocity factor of radio waves near the ground, a BOG antenna can often deliver a radiation pattern similar to an elevated Beverage antenna of roughly twice the length, though with reduced signal strength. A BOG antenna as short as 150 to 200 feet can provide effective receive performance, although a preamplifier may be beneficial in some installations.

The BT-75/BOG is designed for use with 75-ohm RG-6 coaxial cable. Originally developed for television applications, RG-6 offers low loss at VHF and UHF frequencies, resulting in extremely low loss on the 160, 80, and 40-meter bands. Its availability and low cost make it a popular choice for low-band receive antenna feed lines.

The transformer is housed in a NEMA-rated enclosure with stainless steel hardware for long-term outdoor durability. A built-in gas discharge tube across the antenna terminals helps protect the transformer from nearby lightning-induced surges, although it will not provide protection against direct or very close lightning strikes.

For additional information on Beverage antenna construction and performance, refer to Low-Band DXing by ON4UN or the ARRL Antenna Book.

Specifications:

Transformer Size: 3.75 X 2.25 X 1.50 in.

Feed line Impedance: 75 ohm

Antenna Impedance: 300 ohms

RF Connector: F-Type