21-Element Very High Frequency/Ultra High Frequency Log Period Dipole Array
We have two Creative Design CLP5130-1N log periodic antennas in service, one north and one south. The south antenna is dedicated to the e-CALLISTO solar spectrometer described here. The north antenna is used with various receivers for detection of meteor trail reflections and radar echos from the Moon, among other projects.
The LPA antenna installation includes an antenna support structure, antenna rotator, and transmission line. The antenna site is approximately 13 m AMSL and is about 200 m from the shore of Cook Inlet. The antenna uses a braced pipe mast mount as shown in the pictures.
The LPA is a horizontally polarized directional antenna with a gain of approximately 10 dBi and 3 dB beamwidth of approximately 60 degrees, both determined from the manufacturer's datasheet. It is mounted on a rotatable shaft at the top of the pipe mast approximately 12 m above ground level (AGL). The coaxial cable transmission line is 10 mm diameter Terrawave TWS-400 and is approximately 15.5 m long.
The antenna boom length is 2 m and consists of two square aluminum channels, which form a transmission line. The elements are alternated, effectively transposing the transmission line as is necessary for this type of log periodic antenna. The longest element is 1/2-wavelength at 50 MHz (3 m) and the shortest element is approximately 1/2-wavelength at 1300 MHz. The CLP5130-1N weighs about 5 kg.
The antenna control system uses a Yaesu G-450A rotator. The rotator is controlled by an Easy Rotor Control (ERC) rotor controller through ~50 m of 6-conductor outdoor control cable. The ERC is installed in a modified G-450A controller, and its serial port is connected to the laboratory Ethernet LAN through a B&B Electronics ESP904 EIA-232-to-Ethernet converter. This converter's virtual COM port mode allows the rotator to be controlled from a station PC using YO3DMU PstRotator software. Click here for a rotor control diagram.
Photographs of VHF/UHF log periodic antenna - North
