Rhombic Antenna
The rhombic antenna is a highly directional array ideally suited to medium to long haul circuits. Radiation angles vary with the design and ground coefficient but for average ground and a height of approximately a half wavelength, the radiation angle is 35° changing to 15° at 4 fo (Four times the optimum frequency). The main design parameters, i.e. height above ground, leg length and angle between legs, govern the gain of the antenna for a specific frequency.
The simple one wire system has a bandwidth of approximately 2:1, however we have wide experience in the design of this type of antenna and are able to offer arrays with 1, 2 or 3 wires per leg to give a bandwidth of up to 4:1 and, by careful design, gains of 22 dBi are possible.
Rhombic antennas are supplied for powers up to 20kW complete with feeders, terminating resistors or dissipating lines and insulators for mounting on customers' own masts. Alternatively we can supply complete systems designed to customers' requirements with hot dipped galvanised steel tubular or lattice masts or aluminium lattice masts. Astel supply masts painted to ICAO standards complete with lighting kits if required. Balun's are also available for matching to 50 ohm coaxial feeders or alternatively 600 ohm transmission line.
General Specification
| Frequency Range | 3-30MHz |
| Gain | Up to 22 dBi |
| VSWR | Better than 2 : 1 |
| Impedance | 600 ohm (Balun's available for 50 or 75 ohm coaxial feeders) |
| Polarisation | Horizontal |
| Power Rating | Up to 20kw |
| Wind Speed Rating | Up to 120rnph (190kph) |
Construction |
Hard drawn cadmium copper strand, porcelain insulators and acetate spacer insulators for downleads. Balun's and antenna loads, either ground or antenna mounted, dependent upon power rating |