In Yagi antennas, reflector antennas and in-phase excited antennas are suitable for amateur production.
a) Broadband dipole with angular reflector and broadband reflector
Due to the large feedback factor, this antenna is (Fig. 160) Suitable for places with a medium and strong signal, disturbed by reflections from rearward direction, ie especially to urban districts with height segmentation development. The radiation diagram in Fig. 160c applies to the frequency 730 MHz, at which this antenna has the highest gain. The return factor is in the whole scope IV. and V. television band almost uniform. The electrical parameters are shown in Fig. 161. Fig. 162 is a view of the actual embodiment antennas with angled reflector.
b) Excited full-wave floor system for channels Nos. 21 to 81
This antenna (Fig. 163) is very suitable for amateur construction, because is not as demanding on accuracy as Yagi antennas and always gives good results. The reflector wall can be either made of mesh with a mesh size 20 X 20 mm (Fig. 163a), or can be made according to Fig. 163b
In both cases, however, all the wires crossing each other are necessary solder with tin or tin the whole reflector wall in fire (galvanic tinning is not enough). The electrical values are almost equal in the whole band
specific (see also Fig. 171). The antenna is also suitable for places with inhomogeneous ones field, is significantly less sensitive to the quality of the incident field than antennas Yagi type.
The gain of an excited whole-wave floor system can be maintained while maintaining the basic
increase by about 2 dB by adding a series of directors to each emitter (Fig. 164). Director carriers are threaded at both ends, enabling easy installation even in an already finished antenna.
A further increase in gain is achieved by arranging four antennas in the system (Fig. 165). The spacing of the antennas in the axis of the system is chosen so that the distance between individual emitters was constant. The reflectors of these antennas therefore overlap, it is advisable to shorten them accordingly. It is advisable to merge the antennas in series with a parallel connection .
(source : translated from Anteny by Tomas Cesky)
