Another antenna with capacitive loads
For operation in the range of 28 MHz and CB band (27 MHz) can be used "balcony" antenna.
The antenna design is so simple that can easily be repeated at home conditions. It is a flexible steel pin variable diameter from 3 to 1.7 mm. At the end of the pin is located capacitive load as unclosed ring, coaxially with the probe (Fig. 1).
Dimensions are shown for Amateur range 28...30 MHz. The dependence of VSWR with frequency is shown in Fig. 2.
The antenna was mounted horizontally on the balcony of the ninth floor. Counterweight served metal balcony railing, coupled with reinforcement concrete wall. The power to the antenna was received by the 50-Ohm cable, braid which the base of the pin was connected to the fence.
Interestingly, the closure ring increases the resonance frequency of the antenna is 0.5 MHz. The reason is simple: a closed ring has the same capacity, but in unclosed ring "works" and the inductance of the wire. The addition of other metal spokes desirable, and to increase the mechanical stiffness can apply dielectric light spokes and paste.
In the manufacture of the antenna is acceptable to use the pins and tubes are larger, and not definitely variable diameter.
Author: V. Polyakov (RA3AAE)