at 400 MHz. H = horizontal, V = vertical.
Directional characteristic largely independent of frequency
Antenna 2 covers the frequency range from 200 MHz to 500 MHz, making it eminently suitable for interference and spurious signal searches on all communications services within this band, and also includes the 433 MHZ ISM frequency.
A dipole antenna with optimized directional characteristics can be used from 200 MHz onwards. It has a much more pronounced directivity compared to the frame antenna. It also provides high sensitivity with an antenna factor of typically 23 dB(1/m) at 300 to 400 MHz.
Similar types of antenna, known by radio hams as HB9CV, have been used since the 1950s. The principle is based on the combination of two Hertzian dipoles, i.e. dipoles that are short compared to the wavelength. The desired directivity is achieved by connecting the two dipoles in opposite phase and selecting suitable dimensions and spacings.
The directional characteristic in the horizontal plane shows a relatively narrow lobe in the main direction and small minor lobes in the opposite direction. The vertical characteristic is a cardioid similar to that of the frame antenna.
Dipole antenna
200 MHz to 500 MHz
285 mm x 410 mm x 43 mm / 11.2” x 16.1” x 1.7”