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Патент USA US3022517

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Feb. 20, 1962
J. M. BOY-ER
3,022,507
MULTI-FREQUENCY ANTENNA
Filed Oct. 29. 1953
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3 Sheets-Sheet 1
Feb. 20, 1962
.1. M. BOYER
3,022,507
MULTI-FREQUENCY ANTENNA
Filed Oct. 29. 1953
3 Sheets-Sheet 2
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United States Patent 0 "P
3,022,567
Patented Feb. 20., 1962
1
2
a substantially constant input impedance on each of the
3,022,507
lvlULTI-FREQUENCY ANTENNA
Joseph M. Boyer, Redondo Beach, Calif., assignor to
Antenna Engineering Laboratories, Torrance, €aiif., a
limited co-partnership
Filed Oct. 29, 1953, Ser. No. 388,981
6 Ciaims. (Cl. 343—-818)
frequency bands for which it is designed.
Another object of the invention is to provide an antenna
construction embodying the said principal objective which
is simple, of pleasing appearance, which is su?ciently
rugged to withstand adverse weather and other conditions,
and which may be installed and erected in limited space
areas.
This invention relates to antennas for radio wave send
A further object of the invention is to provide a simple,
ing and reception and particularly to an antenna construc 10 multiple frequency band antenna which may be employed
tion for use in the ranges commonly known as short wave,
to excite a non-resonant re?ecting structure such as a
very high, ultra high, and micro wave frequencies.
While in the following speci?cation, the invention will
parabolic re?ector to effect highly directive radiation pat—
terns on several frequency bands.
be described as applied to the so-called short wave range
Still another object of the invention is to provide an
(1 to 30 megacycles) it will be evident to those skilled in 15 antenna element which is e?ective to utilize single fre
the art that the disclosed principles of construction and
quency directive resonant array structures such as the
operation can be readily adapted in the light of such dis
Yagi parasitic array, or combinations of driven array con
closure to other ranges of wave lengths.
?gurations, to obtain e?icient, directive radiation patterns
By way of example, within the short wavevrange, the
therefrom on several frequency bands.
amateur radio operators have been assigned certain short
With the foregoing objects in view, together with such
wave bands by international treaty; said bands being as
additional objects and advantages as may subsequently
follows:
appear, the invention resides in the parts, and in the con
struction, combination and arrangement of parts de
vWave length, meters:
Frequency megacycles
scribed, by way of example, in the following speci?cation
70-80
4—3.5
of certain modes of execution of the invention; reference
4O
7.3-7
being had to the accompanying drawings which form a
2O
__
___
14.3-14
part of said speci?cation and in which drawings:
l5
1O
-
7
~
21.45-21
_
30—28
In the use ,of these bands, the need is for antenna means
which may be used without switching from one ‘band to
, FIG. 1 is a side elevation of an antenna structure em
bodying the present invention; portions being broken away
to disclose interior construction and to reduce the illus
trated length of the antenna,
FIG. 2 is an enlarged, medial sectional view of the
lower end of the antenna shown in FIG. 1,
ing ionospheric propagation conditions so as to employ
FIG. 3 is an enlarged, fragmentary, medial sectional
that band which at the moment is found to be most‘suit 35 view taken on the line 3—3 of FIG. 1 and showing de
another in order to take advantage of, for example, chang
able to maintain reliable communication conditions.
The usual sending and receiving equipment other than
the antenna employed by amateur operators is designed to
operate e?iciently on all of these bands, but usually in
order to operate efhciently on all of these bands the op
erator requires separate antennas for each band and lack
ing either space or the means for such equipment, must
satisfy himself with a compromise antenna with the at
tendant additional tuning and impedance matching means
to enable him to change from hand to band’. Generally
with such equipment, only one band can be employed with 45
ei?ciency which is markedly greater than the other bands;
tails of structure at the upper end of the coaxial line por
tion of the antenna structure,
FIG. 4 is an enlarged, side elevation of the upper end
of the coaxial line portion of the antenna showing the
addition of a means effective to render the antenna ca
pable of sending and receiving signals on at least one fre
quency band in addition to the said at least two other fre
quency bands which may be transmitted or received on the
antenna,
FIG. 5 is a medial sectional view taken on the line 5—5
of FIG. 4,
a
FIG. 6 is a transverse sectional View taken on the line
and, since the antenna is a compromise, even that band
6—6 of FIG. 4,
is not to be operated at an ei?ciency which is equal to the
FIG. 7 is a graph showing the input terminal resistance
maximum performance to be realized when the antenna is
component characteristics of an actual test specimen em
50
perfectly matched to a single wave length. These same
. bodying the construction of the invention shown in FIGS.
considerations apply as well to all other situations in which
1 to 6,
it is desired to send and receive signals selectively on a
FIG. 8 is a series of graphs showing the voltage stand
plurality of discrete wave lengths with a minimum of an
ing wave ratio characteristics of the said test specimen as
tenna equipment and with maximum efliciency and con
measured on 50 ohm characteristic impedance coaxial
venience on each of the wave lengths involved.
cable over the frequency extent of several bands,
The present state of the antenna art includes antennas
FIG. 9 is a series of graphical representations of the
of large cross section in terms of Wave length which may
voltage distribution patterns of the said test specimen
be used over wide frequency bands while maintaining sub
with relation to the graphs shown in FIGS. 8 and 9,
stantially constant input impedance with resultant good
FIG. 10 is a side elevation, partly in section showing
impedance match to the transmission line connected to the 60 a balanced antenna construction embodying features of
antenna terminal, but such antennas are practical only on
the invention,
the very high, ultra high, and micro wave frequency bands
FIG. 11 shows a directive, resonant, multiple frequency
but are impractical for frequency bands between 1 and 30
antenna array embodying features of the invention, and
megacycles due to the fact that the resulting structures
FIG. 12 shows the principles of the embodiment of the
would be so large as to be prohibitive both from size and 65 invention shown in FIG. 10 combined with a non—
cost standpoints.
vHaving the foregoing considerations in mind, the prin- ‘
cipal object of the invention is to provide a single an
tenna which will permit the transmission and reception of
resonant re?ector for directive, multiple frequency
operation.
Referring to the form of the invention shown in FIGS.
1,
2 and 3, the illustrated embodiment of the invention
radio signals on at least two or more widely separated 70 comprises an antenna structure 1 including a hollow ver
frequency bands while maintaining at its input terminal
tical metal tube 2 supported with its lower end spaced
3,022,507
3
siderably less than a quarter wave length at a frequency
of 3.8 mc. and consequently a positive reactance will
appear between the upper end of tube 2 and the point at
which rod 10 emerges through the insulator‘ 12 to form
the tip portion 11 thereof. The current will then ?ow on
the said antenna structure in a pattern having maximum
voltage value at the distal end of said tip and dropping to
secured to the upper end of the tube 4 and having 'a
central opening through which the tube 2 extends and to
which the tube is rigidly ?xed as by welding as best
' shown in FIG. 2.
4
2 and 4, the outer surface of rod 1Q within the tube 2
and the inner surface of the shorting plug 5. The elec
trical length of this folded, shorted, cow'al line is con
above a metal base Plate 3 by a larger and shorter metal
tube 4 mounted on the baseplate 3 and coaxially disposed
with respect to the tube 2 through a shorting plug 5
comprising a flat metal ring having its outer perimeter
The upper end of the tube 2 carries a
laterally extending annular ?ange 6 provided with a series
of eye bolts 6’ to which =guy- wires 7 are attached; said
zero at the base plate 3.
guy wires including insulators 8 interposed therein and
disposed in such proximity to each other along the wire
On- an antenna of the given dimensions, the said posi
tive reactance formed between the opposite ends of the
7 as will not produce resonance on any of the radio free
quency bands on which the antenna operates. At its
insulator 12 will appear to currents of 3.8 mc. frequency
lower end within the tube 4, the tube 2 carries a ring 15 as an inductor or coil interposed in series between the
nearest exterior surface points on the rod 10 and the tube
insulator 9 of good electrical insulating properties and
2 separated by the exterior surface ofthc insulator 12.
The magnitude of the said positive reactance will be deter
mined by the electrical length of the said coaxial line and
good resistance to compression ‘forces held in place there
on by any suitable means such as the rings 9', 9’ welded
to the tube 2 above and below the insulator 9 and this
insulator closely ?ts the inner surface of the tube 4 and 20 the characteristic impedance thereof and results in a sub
stantial reduction in the overall length of the‘ antenna as
combines with the shorting plug 5 and the guy wires 7
to hold the antenna structure erect.
compared with the length of a simple vertical pipe radia
,
Mounted on the plate 3 and extending coaxially through
the tube 2 is a cylindrical metal rod 10 which beyond the
upper'e'nd of the tube terminates in a tapered pointed
portion 11. At the upper'end of the tube, the rod 10 is
thoroughly insulated from the tube 2 by an insulator 12
and within the tube it is held in coaxial alignment with
the interior of the tube by several spaced rings 13 formed
of plastic foam material. Such material (depending on 30
tor for that frequency.
its density) has been found to possess a dielectric con;
stant less than 1.1 with reference to air and it may be as
low as 1.01 to 1.03 and these values for practical purposes
eral force with resultant bowing of the portion of this
'
.
To reduce power loss, it is obvious that in a coaxial
transmission line such as here incorporated in a radio
signal radiator, it is desirable that the insulation between
the inner surfaces shall be air, or at least substantially
air with respect to dielectric constant and loss tangent.
In a location in which the exposed end 11 of the rod
10 would not be subjected to wind‘pressure or other lat
any loss, this material serves to hold the rod 10 centered
rod between the insulator 12 and the base plate 3, or to
shorting as by entrance of moisture as from rain or
dew the insulation could be air only, but since such lo
cations are generally non-existent, it is preferred to pro—
the tube 2. Any suitable means may be employed
vide the centering rings 13 formed of the said plastic foam;
to hold the rings 13 in place within the tube 2 such as
small flanges’14 welded to the rod at each side of each of
a characteristic material being known as Styrafoam, which
rings because of being formed largely of air cells have
are thesame as air, and thus while not materially effecting
the rings 13 to hold the rings in spaced relation while
a low dielectric constant with reference to air and a
the rod and the thus secured rings are assembled into the 40 low loss tangent which is essentially that of air and which
tube 2.
having good resistance to compression, provide the means
by which the rod is maintained centered within the tube
V
In the speci?c example of the invention above described
the following dimensions were embodied as indicated by
the corresponding letters applied to FIG. 1:
Symbol
De?nition
Total height of antenna, feet ________ ._
Base to top of tube 2, feet ____ _
Base to top of tube 4, feet ____ ..
Diameter of tube 4, inches_ - _
Diameter of tube 2, inches _______________ _-
2%
Diameter of rod 10 within tube 2,‘inches-
1%
4
Height of rod 10 above tube 2, feet _____ __
27
Diameter of rod 10 at insulator 12, inches
ll/é
Distance of lower end of tube 2 to base plate, ‘
1%
2. Naturally, the less such insulators are employed, the
greater the e?‘iciency of the antenna, but it has been found
45 that if necessary, the entire cavity between the rod 10 and
the interior of the tube 2 can be ?lled with the said
plastic foam without lowering the efficiency of the an
tenna to a point where it fails to function satisfactorily»
at a plurality of frequencies. Thus, in calculating an
antenna for a given wave length or lengths in which the
so present
invention is incorporated, the presence of the said
insulators can be disregarded and the calculations can
be based on the conducting elements alone.
Referring next to FIGS. 7, 8 and 9 and to those por
tions thereof at the left hand side of each of the ?gures
Assuming now that the base plate 3 of the'antenna 55, ing action of plug 5, a voltage standing Wave pattern will be
' above described which is the feed’ point is connected by
a transmission line L to a radio transmitter Rv operating
at a frequency of 3.8 mc., the radio currents. will travel ,
along the outside surfaces of tube 4 and shorting plug 5
and thence up the outer surface of tube 2 setting up a
60
voltage pattern which is low at thebase plate-‘3 and of
noted that the impedance is su?'iciently close to 50 ohms
to make a good match with a standard transmission line
of that impedance characteristic, that the voltage stand
ing wave ratio is substantially 1:1 and that the voltage
distribution pattern shown in FIG.v 9 indicates that the
entire length of the antenna operates as a quarter wave
substantial value at the, juncture of the upper end of the
radiator; it being noted that in the, region of the said
tube 2 and the insulator 12, at which point they excite
positive reactance, the said voltage distribution pattern
currents throughout the entire extent o-frthe coaxial line 65 departs slightly from a simple sine wave form normally
formed by the inner surface of the tube 2 and therouter
observed in most antennas .. as an incident to that re
surface of the rod 10 within the tube 2. At the lower
actance. It is also to be noted that the impedance curve
' end of the tube 2, the current ?nding the lower; end, of
rises extremely sharply beyond a frequencyof, say 5 mc.,
the'tube spaced from the base plate will, in turn, excite
»so much so, in fact as to render the antenna unusable
currents in the coaxial line formed by’ the outer surface 70 at a frequency above about 5 mo. until, as_wi,ll be here
of the tube 2 and the inner surface of the tube 4 terminat
after discussed, the imposed frequency is such that the
‘ing in an electrical short formed by the shorting plug'5'.
antenna will again resonate.
Thisexcitation of the currentssets up a voltage standing 7'
From the foregoing, it is evident that the above de
wave pattern along the entire inside surfaceyof the shorted,
scribed antennawill operate as an electrical quarter wave
folded coaxial line formed by the inner surfaces of tubes
length vertical radiator working in conjunction with the
Amie-a
3,022,507
t5
5
earth plane and that the eiiect of the said positive re
actance is to reduce the overall height of the antenna
from that which would be required for a simple vertical
pipe radiator for that wave length. The input of this
antenna is approximately 35 to 40 ohms. The radiated
signals are omnidirectional in the horizontal plane and in
the vertical plane are con?ned largely to the horizon
and a pointapproximately 40 degrees above the horizon;
the energy dropping rapidly to zero at higher angles. By
the law of reciprocity, it is evident also that this an 10
tenna will be equally e?icient in reception of signals
within the considered band of 3.5 to 4 mc. On refer
ence to FIG. 8 it will be noted that within this band the
antenna operates with a negligible loss of power between
the transmission line L and the antenna due to change
in base input impedance.
Next, assuming the identical antenna is connected to
circuit across its output terminals; such terminals in this
case being the upper end of the tube 2 and the point on
the rod 10 horizontally adjacent the upper end of the
tube 2. The impedance at this point being extremely
low, the entire length of the antenna contributes to the
operation as a vertical radiator computed as seven eighths
waves in extent. Heretofore, vertical radiators of seven
eighths waves have been regarded as high angle radia
tors, but for some reason not yet factually determined,
the present antenna operates e?iciently at a low, vertical
radiation angle and with a substantial gain over that’ of a
quarter wave vertical antenna operating at that frequency.
The base impedance is still in the region of 40 ohms thus
being a good impedance match for the transmission line
in: O! L. The voltage standing wave ratio is still far less than
the minimum acceptable ratio of 2:1 as shown in FIG. 8.
Referring next to the modi?ed form of the invention
shown in FIGS. 4, 5 and 6, the modi?cation comprises
a transmitter in the band of 7—7.3 mc., and that for
a cage element 15 surrounding the upper end of the tube
example, the transmitter delivers current to the antenna
through transmission line L at 7.15 me. or in the mid 20 2 and comprising an upper metal ?ange 16 ?xed to the
point in that band, the radio frequency currents will
?ow up the outside surfaces of tube 4, shorting plug 5
and tube 2 to the upper end of tube 2, at which point
under side of the ?ange 6 by the eyebolts 6" which for
this purpose in addition to providing anchorage for the
guy wires are provided with longer shanks. A non-con
ductive ?ange 17 surrounds the tube 2 at a distance be
the inner surface of tube 2 and the outer surface of the
rod 10 within tube 2 will be excited and due to the short 25 low the ?ange 16 and is provided with peripheral notches
18 in which the lower ends of a series of vertically dis
ing action of plug 5 a voltage standing wave pattern will be
posed metal rods 19 extending from the ?ange 16 are
set up inside the folded, shorted, coaxial line formed by
anchored in spaced relation to each other and in uniform
the said tubes, rod and shorting plug. However, at the
ly spaced relation radially from the outer surface of the
frequency now under consideration, the said folded,
shorted, coaxial line is electrically a quarter wavelength. 30 tube 2 by a strap 19’. Except for the lower wind re
sistance achieved by this construction, a section of metal
This causes an extremely high resistance to appear be
tubing similarly spaced from the tube 2 might equally
tween the upper end of tube 2 and the horizontally ad
well be employed in place of the rods 19; the use of nine
jacent point on rod 10. The magnitude of this resist.
or more of the said rods being the electrical equivalent
ance because of the exceptionally high Q value of the
of such section of tubing. The length of the rods is such
air insulated, shorted, folded, coaxial line, will, for all 35 that
the length of the antenna below the ?ange 17 is elec
practical purposes disconnect or decouple the portion 11
trically one quarter of the wave length of the center fre
of the rod 10 which projects above and beyond the in
quency of the band to be attained by the use of this at
sulator 12 from the rest of the antenna and only the out
tachment and in the illustrated embodiment is for the
side surface of the antenna below the insulator 12 will
band of l4—l4.4 me. The cage and tube thus form a
radiate. The radiation pattern is similar to that described
shorted quarter wave coaxial line with the tube 2 serving
in connection with operation at 3.8 me.
as the inner conductor.
When the above described transmitter is excited at a
Energy derived from the transmitter R travels up the
frequency of 21.2 mc., the energy from the transmission
outer surfaces of tubes 2 and 4 and shorting plug 5 to
line L will set up currents on the outside surfaces of
the tube 4, shorting plug 5 and tube 2 up to the insu 45 excite currents on the coaxial line formed by that portion
of the tube 2 contained Within the cage structure and
lator 12. At this frequency the voltage will fall to zero
since this coaxial line is shorted at one end, an extremely
at a point one quarter wave-length below the upper end
high resistance or impedance forms between the lower
of the tube 2 and reach a maximum value at said upper
ends of the rods 19 and the horizontally adjacent outer
.end. The previously described decoupling action of the
folded coaxial line formed by the inner surface of the 50 surface of the tube 2 opposite the rods 19 thereby, as
tube 2 and the outer surface ‘of the rod 1%) within the
tube again takes effect. Now, because the portion 11
of the rod is capable of oscillating independently, by
virtue of its electrical length, a 180° phase reversal will
take place between the upper end of the tube 2 and the
horizontally opposite point of the rod 10. The voltage
will fall to a very low value at about the mid point of
the rod tip 11 and rise to a maximum at the tip, op
erating at a high e?iciency due to the low loss inner con
struction which, for all practical purposes, is air. Con
sequently, the antenna now operates as a vertical, phased,
co-linear array as indicated by the voltage distribution
curves in FIG. 9.
On reference to FIG. 7, it will be
noted that the base input impedance is approximately
indicated by measurements, preventing excitation of the
remainder of the antenna. The portion of the antenna
below the ?ange 17 therefore becomes a vertical quarter
wave radiator operating in conjunction with the earth
plane on the said band of 14—14.4 mc., yielding a base
impedance of between 35 to 40 ohms. The presence of
this cage has little effect on a frequency of 3.5-4 me. be
cause the length of the coaxial line formed by the cage is
only 1A6 of a wavelength at that frequency. On the band
of 7-7.3 mc., the cage is 1A; of a wavelength in length and
as is known, a shorted coaxial line which is 1A; of a wave
length in length presents at its input terminals an im
pedance which is equal to the characteristic impedance
of the coaxial line itself. In the present case, the illus
trated design, the spacing between the rods 19 and the
40 ohms a?ording a good match for the transmission 65 surface of the tube 2 is such that this impedance is in
line L, and on reference to FIG. 8, it will be noted that
the neighborhood of 20 ohms and this has little effect
the re?ection power loss e?ect is e?icient and remains
from an inductive standpoint on the performance of the
less than 3% in the region of 21.0-2l.450 mc.
antenna when operating on the 7-7.3 rnc. band. It more
When the transmitter R delivers energy to the antenna
at a frequency of 28.0 to 30 mc., the operation is some 70 exact performance is desired, compensation can be made
by a slight shortening of the tube 2 in those installations
what difierent than that hereinbefore described. Under
in which this modi?cation is used. On the 21-2145 mc.
these conditions,'the inner shorted coaxial line portion
of the antenna is computed as one wavelength electrically
and as is well known in the art a shorted coaxial line
band, this cage has little effect since with relation to that
frequency it is an odd number of eighth waves in length
_ which is electrically one wavelength shows a virtual short 75 with resultant yielding of the same'low series resistance.
aocaso'r
7
3
(3n the 28—3() mc. band, the coaxial line formed by the
cage is one half wave long thereby forming a virtual short
inbefore described can be applied to any parasitic or
driven arraycon?guration with the same capability of'
multiple frequency operation in those con?gurations that
obtains in the ?rst described embodiment of the invention
except as restricted by the physical laws governing the
circuit between the ?ange 17 and tube 2 and consequently
having no appreciable deleterious effect when the antenna
is'operating on this band. It is believed to be’ obvious
that the foregoing modi?cation can thus be applied to
suit other wave lengths on antennas'for other than the
short wave bands so long as the addition thereto does
not in any of the manners above discussed interfere with
the operation of the antenna to which it is added on the
7wave length ‘or lengths for which the antenna is designed
to operate.
Referring nextto‘FlG. 10 there is shown the applica
tion of the invention to a balanced, antenna structure
comprising two identical antennastructures of the same
general form as shown in FIG. 1 disposed with theirbase
or input ends adjacent each other and with the two struc
tures located on a common axial line.
Since the struc
tures are identical, a description of one will su?ice for
both. Such balanced antennas are mounted remote from
a conductive plane and may be disposed at any angle rela
tive to such conductive plane.
'
.
performance of arrays at separately considered single
frequencies.
‘
'
‘ 'By way of example, referring to the embodiment of
the invention shown in FIG. 11, the antenna disclosed
in FIG’. 10 is shown employed as the driven element in
a so-called parasitic or .“Yagi” array. Since the driven
element is identical with that, shown in FIG. 10' the same
numerals are applied thereto and repetition of the struc
ture is omitted. At one side of the driven element is a
reflector element 31 comprising a ?rst metal sleeve 32
of the same diameter as the sleeves .22 of the units com
prising the driven element; said sleeve being longer by
approximately 5% than the distance from the distal end
of one of the sleeves 22 to the distal end of the other
sleeve. 22. 'At its mid length, the sleeve 32 carries a
disc like base member 33 and at each end it is provided
with a shorting plug element 34 corresponding to the
ment ZOhaving a shallow conical'end to the point of
shorting plugs 23 in thc'driven element; each of said
shorting plugs having a coaxially disposed opening there
. which a lead 21 affording connection with a transmis: -
through in which a second tube 35 is secured. Within
' Each antenna structure comprises a metal base ele
sion line L’ common to both structures.
Mounted on
the base element and projectingaway from the pointed
the tube 32 the tubes 35 extend to inner ends 36 spaced
from the adjacent faces of the base member 33; said
tubes being held in coaxial alignment by ‘insulators 37
end of the base element is a metal tube 22 corresponding
in location and function to the tube 4 in the ?rst described
and at their other ends the tubes 35 project beyond the
form of the invention; said tube terminating at its distal 30 shorting plugs to equal extents to an overall length that
end in a metal disk 23 serving both as a shorting plug
is likewise about 5% greater than the overall'length be-.
and, as a mount for a second tube 24 mounted in the
tween the distal ends of the tubes 24 in the driven ele
disk and extending in coaxial relation to the tube 22 to
ment. Mounted in the distal ends of each of, the tubes
an inner end 25 spaced from the inner face of the base
35 is an insulator 38 having a. coaxially disposed open
element 20 and further supported in said coaxial relation
ing extending therethrough in which the mid portion of
by an insulator ring 26 surrounding the tube 24 and en‘
a metal rod 35' is mounted; said rods at one end thereof
gaging the inner surface of the tube 22 in the same man
ner as the insulator 9 in the ?rst described form of the
extending- coaxially through the tubes 35 and being se
cured to the base members ‘33. The distal ends of the
lnverntion.
rods 39 terminate at equal distances beyond the insulators
The tube 24 projects beyond the shorting plug 23 and 40 38 and terminate at an overall dimension which is about
at its distal end carries an insulating plug 27 serving as
5% greater than the overall distance between the distal
an outer support for a metal rod 28 disposed coaxially
ends of the rods 28 of the driven element. The electri—
within the tube and having one end conductively con
cal length of the folded coaxial lines formed by the tubes
nected to the base element at 29 and the other or distal
31 and’ 35 and the shorting plugs 34 are each an elec
end disposed beyond the distal end of the tube 24. The
trical quarterwave length at the frequency at which the
insulator plug 27 in addition to supporting the rod 28,
projecting ends of the rods 28 are decoupled in the driven
also servesrto seal the end of the’ tube against the en
trance of moisture which might result in unwanted loss
in the. operation of the antenna. While air insulation
between the interior parts of the coaxial construction is
the most desirable, in those antennas embodying the last
described construction, the use of one or more insulators
between the rod 28 and the interior of the tube 24 to
'm'aintain the desired coaxial relationship as indicated at
31} ‘can be employed if such insulators are of a character
having a dielectric ‘constant su?‘iciently close to that of
air' as previously discussed. In those antennas of the
last described type, adapted for the longer wave lengths
for which horizontal antennas may be conveniently em
ployed without structural support complications, such in
sulators may be necessary.
or power element.
.
The array also includes a director element 40 in which
all parts are similar to the parts comprising the re?ector
element with the exception that the various overalldi
mensions are about 5% shorter than the corresponding
dimensions of the driven element and except that the
electrical length of the internally folded portion of the
' coaxial line is maintained at the said electrical quarter
wave length. Consequently,the parts thereof have been
given the same numbers as in the re?ector element with
the addition of the exponent “a.”
In installation, the driven element, the reflector’ el -
ment and the'director element aremountedin side by
side relation with the driven element disposed between
the reflector element and the director element. Prefer
ably the distance between the axial lines of the reflector
element and the driven element and between the director
The mode offoperation is believed to be obvious from
the detailed description of the operation of the ?rst de
scribed form of the invention with the additional appli
and driven elements shall not exceed one-quarter of the
cation of known principles of the antenna art to opposed (55 wave length of the highest frequency for which the array
horizontal antenna constructions. The overall electrical
is calculated. Between the'axial lines of the driven ele
length of each‘of the two units is one-quarter of the wave‘
ment and the director element should be approximately
length of the longest frequency for which ‘the antenna
two-thirds the distance between the driven element and
is designed and the electrical length of each unit from
the reflector element.
7
V
the base thereof to the distal end of the tube 24 is one 70
The operation of the’ array is the same as in ‘all simi
quarter of the next highest frequency at which the an
larly arranged single frequency arrays, with. the added
tenna is to be resonant. Additionally, such balanced
advantage of being resonant at two or more frequencies
antennas will operate in, all respects on, other frequencies
inv the, same manners as the previously described vertical
with the production of useful patterns.
It is believed to be obvious from knowledge of the
embodiment. Further, the combination of elements here 75 prior art with respect to single frequency radiators that
3,022,507
10
the above described principles of multi-frequency con
struction of radiators will apply equally well to parasitic
arrays of such radiators as shown in FIG. 11 employing
one-half of the radiators illustrated and erecting them
vertically with reference to a ground plane keeping in
mind the fact that the lateral spacing should not exceed
four times a quarter wave length. Also, radiators such
ductor means including a ?rst tubular conductor coaxial
ly spaced from and surrounding said rod and extending
from a proximal endspaced from said base to a distal
end disposed at a lesser distance from said base than the
distal end of said rod, an annular, laterally projecting con
ductive ?ange carried by said ?rst tubular conductor adja
cent said proximal end thereof, a second tubular conduc
tor coaxially surrounding and spaced from said ?rst tubu
lar conductor and having one end thereof conductivcly
as shown in FIG. 1 may be employed in driven arrays
in which a plurality of such radiatorsof identical form
mitting and receiving apparatus and they may be arranged
attached to said ?ange and having the opposite end there
of extending beyond said proximal end of said ?rst tubu
in any desired spacing and con?guration so long as they
lar member and attached to said base member.
are all contained within a circle of a diameter not to ex
2. An antenna for sending and receiving radio signals
adapted for connection to radio transmitting and receiv
are connected by a common transmission line to the trans
ceed sixteen times a quarter wave length at the highest
frequency at which said radiators are resonant.
In FIG. 12, there is shown an antenna such as disclosed
in FIG. 10 associated or disposed at the focal‘point of a
10
ing apparatus and for operation as a vertical radiator op
erating in connection with a conductive plane such as the
.earth plane comprising a conductive base member which
is a feed point for radio sending and receiving apparatus,
and a rigid internally folded, shorted coaxial transmission
lengths are such that an antenna of this character may 20 line carried by said base and projecting therefrom, said
parabolic re?ector 41. This embodiment of the inven
tion is limited to those higher frequencies whose wave
be mounted in a parabolic re?ector and would be used
only on the ultra high and micro wave frequencies. On
coaxial line comprising a conductive rod having a prox
those frequencies, the small size of the radiating element
makes the positioning thereof at the re?ector focal point
a practical possibility. Since, except for size, the com
from said base, and a coaxially disposed conductor means
also mounted on said base and including a ?rst tubular
ponent parts are the same as shown as in FIG. 10, the
same numbers have been applied thereto with the addi
tion of the exponent “b.” The results of this combina
tion with respect to the directive propagation of signal
are the same as heretofore obtained by the use of parabolic
reflectors with the added capability of sending and receiv
ing signals on a plurality of discrete wave lengths derived
from the antenna construction of the present invention.
The above described embodiments of the invention have
been described with particular respect to their capability
of sending and receiving signals on a plurality of discrete
wave lengths which are harmonically related. This de
rives from the example given of an embodiment of the in‘
vention designed speci?cally for use in connection with
amateur short wave radio bands which by international
treaty are so assigned. However, by way of example,
it is found that speci?c antenna is also resonant at fre
quencies which are of no concern to the amateur, viz.,
bands of 11.4 to 11.9 me. and 19.4 to 19.8 me.
These
frequencies are non-harmonic with respect to the amateur
or so-called “ham” bands. The resonance of the de
scribed antenna at these additional frequencies is the re
sult of the above described construction and is calculable
by the application of known transmission line theory
to the novel coaxial construction.
imal end connected to said base and a distal end remote
conductor coaxially spaced from and surrounding said
rod and extending from a proximal end spaced‘from said
base to a distal end disposed at a lesser distance from
said base than the distal end of said rod, an annular, lat
erally projecting conductive flange carried by said ?rst
tubular member adjacent said proximal end thereof, a
second conductive member coaxially surrounding and
spaced from said ?rst tubular member and having one
end thereof conductively attached to said ?ange and ex
tending from said ?ange to said base and attached to
said base member with resultant support of said ?rst
tubular member with the proximal end thereof spaced
from said base member.
3. An antenna for sending and receiving radio‘ signals
adapted for connection to radio transmitting and receiv
ing apparatus and for operation as a vertical radiator op
erating in connection with a conductive plane such as
the earth plane comprising a conductive base member
which is a feed point for radio sending and receiving ap
paratus, and a rigid internally folded, shorted coaxial
transmission line carried by said base and projecting
therefrom, said coaxial line comprising a conductive rod
having a proximal end connected to said base and a distal
end remote from said base, and a coaxially disposed con
ductor means also mounted on said base and including a
tennas for other 50 ?rst tubular conductor coaxially spaced from and sur
frequencies, not necessarily harmonic, can readily be cal
culated by those skilled in the art in the light of the dis—
closed novel principles of construction through the ap
plication of known formulas on electro-magnetic theory,
it being known that by the law of reciprocity that an
antenna will receive signals on any frequency at which it is
rounding said rod and extending from a proximal end
spaced from said base to a distal end disposed at a lesser
distance from said base than the distal end of said rod, an
annular, laterally projecting conductive ?ange carried by
said ?rst tubular member adjacent said proximal end
thereof, a second conductive member coaxially surround
ing and spaced from said ?rst tubular member and hav
ing one end thereof conductivcly attached to said ?ange
and extending from said ?ange to said base member and
resonant in sending such signals. With these considera
tions in mind, it is appreciated that in the light of the
foregoing disclosure, many variations and modi?cations
will suggest themselves to those skilled in the art and 60 attached to said base member with resultant support of
said ?rst tubular member with the proximal end thereof
therefore, the invention is not to be deemed to be limited
spaced from said base member; said ?rst tubular member
to the exact forms hereinbefo-re disclosed by way of ex
further including an external coaxial line at the distal end
ample, but to include as well all such changes and mod
thereof.
i?cations in the parts and in the construction, combina
4. An antenna for sending and receiving radio signals
tion and arrangement of parts as shall come within the
purview of the appended claims.
I claim:
1. An antenna for sending and receiving radio signals
comprising a conductive base member which is a feed
point for radio sending and receiving apparatus, and a
rigid internally folded, shorted coaxial transmission line
carried by said base, said coaxial line comprising an in
ner conductive rod having a proximal end‘connected to
said base and a distal end remote from said base and ex
over any one of a plurality of separate frequencies and
disposed remote from a conductive plane; said antenna
comprising a pair of identical units arranged in opposed
end to end relation along a common axial line above a
conductive plane; each of said units comprising a con
ductive base member which is a feed point, a conductive
rod having a proximal end thereof ?xed to said base mem
ber and projecting therefrom along said axial line to a
distal end remote from said base, a tubular conductive
tending out of said line, and a coaxially disposed con 75 member coaxially surrounding and spaced from said rod
3,022,507
,
i1
7
12
r
and including a proximal end adjacent to and spaced from
said base member and, a distal end disposed at a lesser
distance from saidbase member than the distal end of
gaging the outer surface of said inner member and the
‘inner wall surface of said tubular member; said material
having a dielectric constant which, with reference to air, is
not greater than‘ 1.1:1.
said rod, conductive means‘ comprising an internally
folded, shorted, end ?xed to said ,base' member and sup
porting said'tubnlar'member on said base member in co~
References Cited in the ?le of this patent
axial relation to said rod and with the proximal end of
UNITED STATES PATENTS I
said tubular member spaced from said base member; the
base'members of each of said units being positioned in
2,184,729
Bailey _.._‘_'_ _________ __ Dec. 26, 1939
proximity to each other and being'adaptecl' for common 10 2,205,874 , Buschbeck __._'________ __ June 25, 1940
' connection to radio transmitting and receiving apparatus.
5. The combination with an antennaras claimed in
claim '4 of a parabolic radio wave re?ector surface ar
2,229,865
Morgan -Q. _______ _'_____ Jan. 28, 1941
2,256,608
Braden _____________ -2- Sept. 23, 1941
2,274,389
Von Baeyer et al ______ __ Feb. 24, 1942
' ranged with the focal point thereof substantially coinci
2,275,342
dent with the mid lengthof the axis of the antenna.
15 2,284,434
6. In an antenna for sending and receiving radio sig
r 2,297,512
nals and comprising a coaxial line havinga tubular outer
2,297,513
Lindenblad .. _________ __ May 26, ‘1942
conductirre member and an inner conductive member dis
posed within and coaxially spaced from the inner. walls ,
of said tubular member, said inner conductive member ‘20
and said outer conductive member being connected to
gether at one end to form a feed point for the antenna,
said’ inner conductive member extending outwardly of
said outer member, said inner member and outer member
Von Baeyer ______ __'-..__ Sept. 29, 1942
Von Baeyer _______ __,___ Sept. 29, 1942
2,417,808
Carter __________ _'____._ Mar. 25, 1947
2,462,443
' 2,509,253
Wehner _.'_ ____________ __ Feb. 22,1949
Schriefer ____________ __ May 30, 1950'
2,512,078
Wehner ..____' ____ __'____VJune 20, 1950
2,531,476
,Schriefer ____________ __ Nov. 28, 1950
2,535,298
2,539,680
being radiating elements and said'inner member being 25
2,648,768
maintained in said coaxial relation to said tubular mem
2,802,210
ber comprising rigid, porous, non-conductive material en~
Brown ________ _'_ _____ __ Mar. 3, 1942
Lattin ___'__...;___.._;_"___ Dec. 26, 1950
,
Wehner _____________ __ Jan. 30, 1951
Woodward __________ __ Aug. 11, 1953
,
Berndt ______________ _._ Aug. 6, 1957
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