Antenna "ORION-5/8" mass-produced DM is working with the base radio citizen's band 27 MHz. The main advantage of this antenna is that the main lobe of the directivity pattern in the vertical plane has a minimum angle (Fig. 1).
Fig.1
This means that most of the energy radiated by the transmitter, concentrated near the earth's surface that makes best use of low power transmitters. The length of the vibrator is 5/8 wavelength. The resonance of the antenna is achieved by including the extension of the coil, which contains 8 turns with a diameter of 40 mm, the winding length of about 100mm. Wound coil wire or bus bar cross section of at least 2 mm2.
Specifications:
The gain - 6 dB;
Input impedance - 50 Ohms;
SWR less than 1.5;
Bandwidth - 26,5 - 28,2 MHz;
The radiation pattern in the horizontal plane is circular; -vertical - see Fig.1.;
Wind load - 25 m/s;
Weight - 2.7 kg.
When installing the antenna, it is desirable to adjust. For this purpose, measuring SWR on the selected channel, set the desired length of the coil. If the signal strength is below the coil extend, and Vice versa.
Fig.2
Author: RCB, Moscow; Publication: N. Bolshakov, rf.atnn.ru