Helical antenna for portable radio
The helical antenna is intended installation on the radio personal use in portable variant. Compared to the telescopic whip antenna spiral has a smaller size in length, which creates a lot of advantages when using the radio stations in the city. Despite its small size, this antenna has greater flexibility without breaking electrical contact, which is not true of the telescopic antenna, which often loses mezhkolennye contact and requires more careful treatment. But, most importantly, the efficiency of the antenna type "spiral" on the field strength of 1.2 - 1.5 times that of the whip antenna with a typical size of 525 mm.
The results of the experimental data in two ways communication with whip and helical antennas - show a clear advantage of the latter. Thus, when the transmitter output power of 0.2 W, and receiver sensitivity of 1.5 - 2.0 µv range strong connection between the same type of radio stations in the city with spiral antennas were 1.4 km, 0.5 km more than with a male.
The workpiece material antenna serves as polyethylene, or any other used for the production of high-frequency cables. In Fig.1 shows the size and design of this piece.
Forming a threaded connection in the simplest case is made by heating the blank in the body of the connector SR-50-FV.
The placement of the windings on the workpiece shown in Fig.2. Winding I contains.80 turns of wire wound round on a plot of length 34 mm Winding II contains 29 turns of wire, placed evenly along the winding length of 150 mm. Both windings is made by cable brand sew-2 0.4 mm. Fixed end of the winding method of the mould wire in polyethylene.
Adjusting the antenna is in resonance method rollback or domode one or two turns of wire on the connector side. Resonance is achieved by the maximum power output of the transmitter that is logged by the device field strength or any spectrum analyzer at a distance of not less than 2 meters. After you have configured the antenna must be placed in a flexible waterproof casing.
General view of the antenna in the collection shown in Fig.3.
Author: Sergei Sushko, Tyumen; Publication: N. Bolshakov, rf.atnn.ru