JPH03280604A - Vhf television antenna - Google Patents

Abstract

PURPOSE:To improve the front-to-back ratio of the antenna at a VHF low channel and to realize a VHF television antenna at a low cost with a light weight by arranging a low-channel composite director adjacently to VHF high channel directions onto an arm. CONSTITUTION:The antenna is provided with plural VHF high channel directors 6 arranged on an arm 4 at a prescribed interval and with a VHF low channel director 22 between the VHF high channel directors arranged side by side on the arm. The VHF low channel director 22 consists of two composite directors with an inductor provided therein and arranged side by side closely. That is, since the VHF low channel director 22 is arranged on the arm, a vertical arm or the like to support the VHF low channel director 22 is not required, and the front-to-back ratio of the antenna at the VHF low channel is improved by selecting the inductance of the composite directors to be nearly 370nH and the interval between the composite directors to be nearly 50mm. Thus, the VHF television antenna is realized at a low cost with a light weight.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a VHF television antenna, and particularly to a full-band antenna that can receive both VHF high and low channels well.

[Prior Art] Conventionally, there is a VHF antenna for all bands as shown in FIG. In the same figure, 2 is a column, 4 is an arm, and a VHF high channel is installed at a predetermined interval from one end of the arm 4 (the left end in FIG. 8) to the right end along its length. Waveguides 6.6 for VHF high channel are arranged, and these waveguides 6.6 for VHF high channel
A vertical arm 8 is provided between two adjacent ones of the two, and VHF low channel waveguides 10 and 10 are provided at both upper and lower ends of the vertical arm 8. These waveguides 10.10 are composite waveguides in which an inductor is inserted in the center to shorten the overall length. In addition, shortened composite waveguides are used for shortened and stitched ordinary VH.
The waveguide for the F low channel is designed to block the propagation of radio waves in the NHF high channel.For example, a composite waveguide has a total length of about 900 nm and an inductance of about 270 nH (one type is used). A radiator 12 that serves as both a VHF high channel and a low channel is provided further to the right end than the right end of the VHF high channel waveguide 6 of the arm 2. A vertical arm 14 is provided on the side, and low channel reflectors 16 and 16 are provided at both upper and lower ends of the vertical arm 14.A VHF high channel reflector is provided on the arm 2 on the right end side of the vertical arm 14. A reflector 18 is provided, and a reflector 20 for the VHF low channel is further provided on the right end side of the reflector 1z.

[Problems to be Solved by the Invention] The above antenna improves the front-to-back ratio of the VHF low channel in order to remove multi-ghosts that tend to occur in the VHF low channel, and for this purpose, a reflector for the VHF low channel is used. Three VHF low channel composite waveguides 10 are provided. especially,
The reason why two composite waveguides 1o are provided is that with one composite waveguide 1o, a large amount of current flows through its inductor, resulting in poor efficiency. In order to support these two composite waveguides 1o, it is necessary to provide a vertical arm 8 or to attach a metal fitting to attach this vertical arm 8 to the arm 4, and the weight of this metal fitting and the vertical arm 8 increases. However, there were problems in that the antenna was heavy, and the cost of the vertical arm 8 and its mounting increased due to the need for metal fittings. moreover,
Providing the vertical arm 8 increases the wind receiving area, which also poses a problem in that it becomes weaker against the wind.

An object of the present invention is to provide a VHF antenna that solves the above problems.

[Means for Solving the Problems] In order to achieve the above object, the present invention includes an arm and a plurality of VHF eights arranged on the arm at predetermined intervals along the length of the arm. a channel waveguide, and a VHF low channel waveguide disposed on the arm between the adjacent VHF eight channel waveguides,
The 5 VHF low channel waveguide is made up of two composite waveguides each having an inductor inside, and these composite waveguides are arranged close to each other.

As a composite waveguide, its total length is approximately 9DOmm, and the inductance of its inductor is greater than 270nH□0
The sound level is preferably smaller than 440nH, and about 37O
n) It is most desirable to set it to l. Also, the spacing between the composite waveguides is approximately 50 mm or more.

[Function] According to the present invention, since the VHF high channel multiple 15 waveguide is arranged on the arm, there is a vertical arm for supporting them, and a vertical arm for fixing this vertical arm on the arm. There is no need for metal fittings, etc., and the area of blown air is also reduced.

In addition, the total length of the composite waveguide is approximately 9DOm■, and its in- 2o
When the inductance of the taffeta is about 370 nH and the spacing between the composite waveguides is about 501 stations, the front-to-back ratio in the VHF low channel is improved.

[Example] One embodiment of the invention is shown in FIGS. 1-3.

In both figures, 2 is the column, 4 is the arm, and 6 is HF.
The waveguide 12 for the 8V channel is a VHF high channel and low channel radiator, 14 is a vertical arm, 1
6.20 is a reflector for VHF low channel, 18 is VH
This is a reflector for F high channel.

These are similar to the conventional VHF television antenna shown in Figure s8.

The VHF high channel waveguides 6 are arranged at intervals of approximately 2501cm, and these VHF high channel waveguides 6
Of these, two VHF low channel waveguides 22 are provided directly above the ar between the second and third grains counting from the VHF high channel and low channel radiators 12 in FIGS. 1 and 2. It is being That is, the distance between the centers of the VHF high channel and low channel waveguides 22 and the centers of the two low channel waveguides 22 is approximately 400 mm.
■It is set to Oboro.

As shown in FIG. 3, each of these VHF low channel waveguides 22 has a length of about 900 m
The inductor 24 has an inductance of, for example, 370 nH in its center. These VHF low channel composite waveguides 22 are connected to the two-port VHF high channel waveguide 6 from the VHF high channel and low channel radiators 12 so that the distance between them is approximately 50 mm, for example. They are located approximately 1001 degrees apart from the VHF high channel waveguide 6 with the same third grain.

The reason why the inductance of the inductor 24 is set to 370 nH is as follows. It is generally known that in Yagi antennas, the reception bandwidth can be widened by making the waveguide or reflector elements thicker or by arranging multiple elements at the same location. The present invention also utilizes this principle, and the composite waveguides 22 are arranged closely for the above purpose. However, the composite waveguide 22 must operate so as to perform a waveguiding function in the VHF low channel and not to have a reflecting function in the VHF high channel 0 50 . As mentioned above, the composite waveguide 10 used in the conventional VHF television antenna shown in FIG.
0), the inductance of the inductor inserted in the center is approximately 270 nH, but when two of these composite waveguides 10 are placed close to each other as in this embodiment, the frequency in the high channel shown by the dotted line in FIG. As is clear from the gain characteristics, it has a reflection effect in the VHF high channel. For comparison, the frequency versus gain characteristic in the VHF high channel in the case where no composite waveguide is provided is shown in FIG. 4 by a dashed line.

This reflection effect is caused by the fact that the two composite waveguides are placed close to each other, which creates capacitive coupling between the two composite waveguides, and the inductors of the two composite waveguides are connected in parallel. It is thought that the inductance decreases dynamically as it approaches a connected state, and the inductor does not become a high impedance in the VHF high channel, and high frequency current flows between the elements on both sides of the inductor. 5. Therefore, it is necessary for the inductor 24 to have an inductance larger than 270 nH.

Also, in order to achieve high impedance in the VHF high channel, the larger the inductance of the inductor 24 is, the better; if it is too large, the impedance will become high on the high frequency side in the VHF low channel, and the elements on both sides of the inductor 24 The high frequency current of the VHF low channel will no longer flow. For example, if the inductance of the inductor 24 is 440nFI,
As shown by the dotted line in FIG. 5, the gain rapidly decreases from around 105 MH. For comparison, the figure shows the frequency vs. gain characteristic in the case where only one composite waveguide whose inductance of the inductor 24 is 270 nH is provided as a dashed line. Therefore, it is desirable that the inductance of the inductor 24 is smaller than 440 nH. Therefore, in this example:
The inductance of the inductor 24 is selected to be greater than 270 nH and smaller than 440 nH: 170 nH.

The number vs. gain characteristic is shown as a solid line in FIG. 4, and the frequency vs. gain characteristic in the VHF low channel is shown as a solid line in FIG. Fourth
As is clear from the figure, when the inductance of the inductor 24 is 370 nH, the gain in the VHF high channel is larger than when the composite waveguide shown by the dashed line is not provided. In the conventional device shown in FIG. 8, since the composite waveguides 10 and 10 are provided at both the upper and lower ends of the vertical arm 8, the distance between the two composite waveguides 10 is wide, and each Even if a composite waveguide 10.10 is provided, because the length of a certain element is significantly shorter than 1/2 wavelength of the VHF high channel, these elements do not exhibit a waveguiding effect in the VHF high channel, and the The gain vs. frequency characteristics are the same as when no composite waveguide is provided, as shown by the dotted line in Figure 4. However, in this embodiment, since the two composite waveguides are placed close to each other, interaction occurs between them, and the elements on both sides of the inductor of each composite waveguide 22 have equal dynamic differences. is longer than the actual length, but the gain in the VHF high channel is greater than in the case where the composite waveguide shown by the dashed line is not provided. That is, as an effect of placing the composite waveguide 22 close to each other, the gain of the VHF high channel increases.

Also, as is clear from Figure 145, the gain in the VHF low channel is determined by increasing the inductance of the inductor by 27
The gain is larger than when one composite waveguide with 0 nH is provided (indicated by a - dotted chain line).

Furthermore, when the inductance of the inductor 24 is selected in this way, the front/rear ratio vs. frequency characteristic in the VHF high channel is as shown in Figure 6.Although not shown in the figure, this characteristic is shown in Figure 8. This is almost the same as the front-to-back ratio vs. frequency characteristic in the VHF eight channel of a conventional VHF television antenna. Further, the front-rear ratio vs. frequency characteristic in the VHF low channel is shown by the solid line in FIG. 7, and the front-rear ratio vs. frequency characteristic in the conventional VHF low channel shown in FIG. The front-to-back ratio vs. frequency characteristic in the VHF low channel is improved compared to the case where only one composite waveguide whose inductance is 27 On)l is provided as shown by the dashed line in the figure.

Further, the reason why the spacing between the composite waveguides 22 is set to approximately 50 mm is as follows. The smaller the spacing between the composite waveguides 22, the better the waveguiding effect in the VHF high channel, but the inductance of the inductor 24 must be correspondingly increased, which lowers the efficiency. Conversely, if the spacing between the composite waveguides 22 is widened, the composite waveguides 22 will be closer to the VHF high channel waveguide 6, and an adverse effect will occur due to interaction with this waveguide. Taking these into consideration, the composite waveguide 2
2 is selected to be approximately 50i+v+.

[Effects of the Invention] As described above, according to the present invention, by providing the composite waveguides close to each other on the arm, the front-to-back ratio in the VHF low channel can be improved compared to the conventional one, and the vertical Since there is no need to install a composite waveguide on the arm, there is no need for a vertical arm or any metal fittings to support it on the arm, making it a lower cost, lighter weight, and higher performance VHF TV than conventional ones. An antenna can be realized.

[Brief explanation of drawings]

FIG. 1 is a plan view of one embodiment of the VHF television antenna according to the present invention, FIG. 2 is a side view of the same embodiment, FIG. 3 is a diagram schematically showing a composite waveguide used in the same embodiment, and FIG. Figure 4 is a frequency vs. gain characteristic diagram in the VHF high channel between the same example and comparative example, Figure 5 is a frequency vs. gain characteristic diagram in the VHF low channel between the same example and comparative example, and Figure 6 is the same example. FIG. 7 is a frequency vs. front-to-back ratio characteristic diagram in the VHF high channel of the same embodiment and a comparative example, and FIG. 8 is a side view of a conventional VHF television antenna. 4...Arm, 6...VHF high channel waveguide, 22...VHF high channel composite waveguide, 24...Inductor. Prefectural Seki No. 3 Kuniaki Toki Shikishigei (MH2) Yasue Kabuto (MHz)

Claims (3)

[Claims] (1) An arm, a plurality of VHF high channel waveguides arranged on the arm at predetermined intervals in the length direction, and on the arm between the adjacent VHF high channel waveguides. and a VHF low channel waveguide arranged in the VHF low channel waveguide. A VHF television antenna characterized by being placed closely together. (2) In the VHF television antenna according to claim 1, the total length of the composite waveguide is about 900 mm, and the inductance of the inductor of the composite waveguide is larger than 270 nH and smaller than 440 nH, and A VH characterized in that the spacing between waveguides is approximately 50 mm.
F TV antenna. (3) In the VHF television antenna according to claim 2, the inductance of the inductor of the composite device is about 370 nH.
A VHF television antenna characterized by: