Whip-type antenna which can slide-adjust the tuning frequency

In a whip-type antenna which can be used for either mobile or fixed station, the improvement is characterized in that the antenna has at least a portion of an antenna element thereof wound in turns so as to impart the inductance to the antenna element and a power-operated motor is capable of varying the turns and pitches of the above wound antenna element for varying the inductance, which leads to the variation of tuning frequency of the antenna.

BACKGROUND OF INVENTION 
This invention relates to a radio antenna of either mobile or fixed station 
which provides a remote control of a tuning frequency that the antenna 
receives or transmits. 
These days, the number of cars which are equipped with radio systems has 
remarkably increased. Those systems available for amateur radio operators 
have particularly increased in number and accordingly the radio technique 
in the amateur radio field has shown a remarkable progress such that the 
radio system has become compact and shown improved performance. Eventually 
this improvement has led to the advent of a radio system, which has a 
number of bands, yet can be mounted onto a vehicle. 
In view of the above situation an improvement also has been requested in 
view of antenna which preferably can cover a number of bands with a single 
antenna element thereof. 
The following types of antennas have been popularly used as antennas which 
can cover a number of bands: 
(a) a whip-type antenna which is provided with replaceable inductance coil 
at the middle thereof, 
(b) a whip-type antenna having a variable inductance coil at the middle 
thereof wherein inductance of the coil is variable manually or by a 
power-operated motor, and 
(c) a whip-type antenna having three kinds of inductance coils at the 
middle of the whip antenna. 
However, these antennas are less than optimal in their performance and 
appearance due to the constructional restriction set forth above. Namely, 
in view of the performance of above whip-type antennas, the variation of 
inductance which corresponds to the variation of tuning frequency has been 
conducted either by the replacement of the inductance coil or the 
inductance variation of the short coil attached to the middle of the 
antenna so that the tuning frequency that such antennas can cover is 
defined to a limited range and the replacing operation is cumbersome. 
Accordingly, it is an object of the present invention to provide a 
whip-type antenna which can vary the tuning frequency in a wide range 
overcoming the defects of conventional whip-type antenna. 
It is another object of the present invention to provide a whip-type 
antenna which is characterized in that the tuning frequency of the whip 
antenna is varied corresponding to the variation of turns or pitch of 
loading (inductance) coils which is conducted by a power-operated motor. 
Although the invention is illustrated and described in relationship to 
specific embodiments, it is nevertheless not intended to be limited to the 
details shown, since various modifications and structural changes may be 
made therein without departing from the spirit of the invention and within 
the scope and range of equivalents of the claims. 
The construction and operation of the invention, however, together with 
additional objects and advantages, thereof, will be best understood from 
the following description of specific embodiments when read in connection 
with the accompanying drawings.

DETAILED DESCRIPTION OF DISCLOSURE 
The whip-type antenna of this invention is described hereinafter in the 
following embodiments in conjunction with attached drawings. 
FIRST EMBODIMENT 
In FIG. 1, a rod antenna 2 which can be extended or retracted in a 
telescopic manner is mounted on a metallic body 1 of a vehicle such that 
the proximal end of the antenna 2 is secured to the metallic body 1. 
Within the rod antenna 2, an antenna element or conductor 3 which is 
extruded in a flexible insulating tube 4 of high material strength 
(preferably made of polyacetal) is suitably disposed in a concentric 
manner having the upper extremity thereof secured to the top 5 of the rod 
antenna 2. 
This antenna element 3 has at least the lower portion reeled into a reel 
casing 6, the construction of which is described later in detail. 
Due to the above construction, the antenna element 3 can be either raised 
or lowered corresponding to the elevation of the rod antenna 2. 
A matching circuit 7 which comprises a matching coil 8 and a matching 
condenser 9 is disposed just below the proximal end of the antenna 2 and 
within the metallic body 1. This matching condenser 9 has one end 
connected with one corresponding end of a feeder 10 which, in turn, has 
another end connected with either a radio transmitting or receiving device 
(not shown in the drawings). 
The above condenser 9 has another end connected with the corresponding end 
of the above matching coil 8 as well as the corresponding end of an 
auxiliary coil 11. This auxiliary coil 11 has another end connected with a 
slide ring 12 which is fixedly secured to the inner periphery of a reel 
cover 13 which is made of an insulating material and forms a part of the 
reel casing 6. (Please refer to FIG. 3) 
Referring now to the reel casing 6, the above flexible antenna element 3 
has some portion thereof wound like a coil in a drive reel 14 which is 
driven by a power-operated motor 15 by way of a worm 16a and a worm wheel 
16b. This antenna 2 is further constructed such that the antenna element 3 
has one end thereof provided with a brush 17 which biasingly and slidably 
come in contact with the slide ring 12 and has other end secured to the 
inner extremity 2 of the rod antenna element 3 as described before. 
Referring now to the operation of the whip antenna of this invention which 
has the above construction, the current of high frequency carried from the 
transmitter reaches the slide ring 12 by way of the feeder 10, the 
matching circuit 7 and the auxiliary coil 11. Thus carried high frequency 
current is further carried to the antenna element 3 by way of a slide 
engagement between the stationary slide ring 12 and the rotatable brush 
terminal 17 which is disposed in the drive wheel 14. When the antenna 
element 3 is reeled into the drive reel 14 by means of the power-operated 
motor 15, the inductance L of the reeled antenna element 3 becomes larger 
and correspondingly the tuning frequency of the entire antenna becomes 
lower. When the antenna element 3 is reeled out from the drive wheel 14, 
the above inductance decreases and the tuning frequency becomes higher. 
This implies that a desired matching point or frequency is obtainable by 
adjusting the reeling amount of the antenna element 3 which is imparted by 
the actuation of the power-operated motor 15. 
Since the variation of the inductance caused by the reeling of the antenna 
element in or out from the drive reel 14 is far greater than the variation 
of inductance caused by either extension or retraction of the antenna 
element 7, the tuning frequency moves toward higher frequency 
corresponding to the extension of the rod antenna 2. In this first 
embodiment, the tuning frequency could be continuously varied from 18 MHZ 
to 29 MHZ. 
Furthermore the whip-type antenna of this invention is provided with 
following additional constructions which feature the above antenna. 
Namely, the auxiliary coil 11 which is disposed between the matching 
circuit 7 and the reel 14 is replaceably mounted. Therefore, with the 
provision of various kinds of coils 11 which differ in diameter, pitch or 
total length with each other the adjustment of tuning frequency band is 
achieved. 
Meanwhile, since the whip-type antenna(rod antenna) of this embodiment is 
constructed in a telescopic manner, the entire antenna can be 
substantially hidden into the car body 1 when the antenna is retracted to 
the lowest position, the antenna be prevented from steal or damage. 
Accordingly, the whip-type antenna of this embodiment has the following 
advantages. 
(i) A single antenna can cover a multiple number of bands. 
(ii) Since the rod antenna is made of a telescopic construction, the rod is 
almost hidden in the vehicle body when it is retracted to the lowest level 
whereby the aesthetic effect of the vehicle equipped with such antenna 
cannot be damaged. 
SECOND EMBODIMENT 
The whip-type antenna of this embodiment is devised from the idea that if 
the tuning frequency can be varied merely by the manipulation of the drive 
reel 14 while maintaining the height of the rod antenna 2 at a constant 
level, the tuning frequency varies in a range much wider than that of the 
first embodiment. As can be observed easily from FIG. 6, the vehicle body 
1, a power-operated mechanism 15, a reeling mechanism 14 and a feeding 
circuit 10 of the antenna of this embodiment correspond to those of the 
first embodiment. 
The improvement which characterizes this second embodiment is that a rod 
antenna 18 of a metallic pipe construction is mounted on the vehicle body 
in place and a flexible antenna element 19 is elevatably disposed relative 
to and in the rod antenna 18. This element 19 is further provided with a 
contactor 20 which slidably comes into contact with the inner periphery of 
the metal-made rod antenna 18. 
To be more specific, the above contactor 20 which has the equidistant 
longitudinal slits biasingly comes into contact with the inner side of the 
rod antenna 18 and is slidable within the rod antenna 18 while maintaining 
above contact engagement. The contactor 20 is secured to the top extremity 
of the antenna element 19 preferably by soldering. 
Due to the above construction, the above contactor 20 elevates or goes down 
corresponding to the reeling-out or reeling-in of the antenna 18 relative 
to the drive reel 14. Accordingly, the rod antenna 18 maintains the 
constant length irrespective of the elevation of antenna element 19 so 
that the tuning frequency is greatly varied corresponding to the number of 
turns or diameter of turns of the antenna element 19 wound in the drive 
reel 14. 
The operating principle set forth in the above embodiment is applicable not 
only to mobile stations such as vehicles but also fixed stations. 
Namely, the vehicle body is replaceable with a steel tower. 
FIG. 7 shows the modification of above whip-type antenna wherein the 
improvement is characterized in that the rod antenna 21 comprises an upper 
portion 22 and a lower portion 23 which are connected by a junction 24. 
Depending upon the wave length of the radio wave to be received ot 
transmitted, the antenna of a considerable length may be required. This 
modified antenna is especially applicable in such a case wherein the 
antenna can be bent as shown in FIG. 6 when it is out of operation.