AX-81S Active HF Antenna

The AX-81S antenna is a compact active HF antenna, ruggedized to suit harsh outdoor environments, and particularly suitable for marine environments. While it has been designed primarily as a marine antenna, it can be useful anywhere where good HF performance and reliability are required, and where space is at premium. The antenna is receive-only, and is suitable for professional as well as consumer applications.

The antenna covers the frequency range of 2 to 30 MHz, or 300 kHz to 50 MHz with somewhat reduced (but still excellent) performance.

While designed to be entirely general-purpose, the AX-81S antenna is especially suitable for the WiNRADiO G33EM marine receivers and G3 series of HF receivers.

The principal elements of the antenna are constructed of a low-carbon austenitic stainless steel that contains molybdenum. Austenitic (chromium and nickel content) stainless steels have high ductility (i.e. ability of a metal to plastically deform without breaking or fracturing), low yield stress and high ultimate tensile strength, when compared to a typical carbon steel. The 316L grade as used for the AX-81S antenna also offers an especially high degree of resistance to corrosion. The choice of materials and the durable construction of the AX-81S antenna will ensure trouble-free operation for many years.

The antenna was designed for rapid installation, with an easy-to-follow installation procedure supplied with the antenna.

Optional accessories

The WR-AC-RMB-114 heavy duty rail-mount antenna base has a single swivelling mount. It accepts any standard antenna with a 1" diameter standard #14 thread (such as the AX-81S antenna) and can be mounted on a railing of 7/8 to 1" diameter. Material is stainless steel 316 grade.

The WR-AC-DMB-114 heavy duty deck-mount antenna base has two swivelling mounts for complete adjustability. It accepts any standard antenna with a 1" diameter standard #14 thread (such as the AX-81S antenna). Material is stainless steel 316 grade.

The WR-CMC-30 Common-Mode Choke eliminates common-mode noise from the antenna feedline, resulting in a considerable increase of the received signal quality. Common-mode noise is generated by computers and other electric or electronic appliances, and can be a problem especially in the lower portions of HF spectrum. The Common-Mode Choke can be also very useful to provide an alternative earthing point if the AX-81S antenna itself cannot be grounded due to its location, or its ground connection is inadequate.

The WR-BT-650 Power Injector (Bias "T") provides a means of injecting DC power in a coaxial cable, to power the antenna from a remotely located power supply. It features a flat frequency response and low insertion loss. Note that the Power Injector is not required if the AX-81S antenna is used with the WiNRADiO G33EM receiver which already provides suitable power for the antenna at the receiver's antenna input. For other applications, we recommend using WiNRADiO SF-41 range of low-noise power supplies.