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The Astroplane Avanti antenna was invented by Louis J. And Herbert R. Martino Blaese at the end of the
sixties and patented in 1971 under registration number 3587109.
At that time CB was very fashionable, the equipment operators employed used 23 channels, and a height
limitation was imposed so that the antenna could not exceed 20 feet above the maximum height of the
building that existed on the property. This limitation was the Achilles heel of the vertical antennas Avanti
sold that were 1/4 and 5/8 wavelength, and usually fed at the base. The reason was simple. The Avanti
Astroplane antenna emits from the top, the other antennas cited do it nearer the base. This result was
whenthe Avanti Astroplane, and the other verticals were mounted at the maximum permitted height of 20
feet, the Astroplane had more coverage to radiate from a greater height.
The Avanti in Figure 1 left shows three sections of 1/4 wavelength. At 27 MHz the wavelength is 11 meters,
so that 3/4 wave require 8.27 meters, or 27 feet, and this exceeds the maximum height of 20 feet allowed
when muntedon a building.
Figure 1. Original concept
The solution that Martino found was to cut the physical length of the element about 1/8 wavelength. The
result was the antenna would have two lower sections of 1/4 wavelength, and an upper 1/8, as shown in
Figure 1 right , reaching a height of 6.82 meters. With the shortening, due to the shape of the antenna and
the type of material used, the Astroplane would perfectly meet the standard maximum height of 20 feet
above a structure.
To shorten the antenna Martino employed a well known system called top loading, see Figures 2 and 3. The
upper load electrically lengthened the allowed upper element of 1/8 wavelength to 1/4 wavelength. This
means that although this element physically measured 1/8 wavelength, because of the top loading, the
upper section had a electrical equivalent of 1/4 wavelength. How much longer? It depends on the
dimensions of the top load. In this case the load elements of the crossed Capacitor Hat are constructed of
1/8 wavelength radials, and resulted in the 1/8 element achieving an electrical length of 1/4 wave. See
Figure 4.
Figure 2. T higher load on the antenna used Titanic
Figure 3. Higher load types for antennas
Figure 4 shows two antennas Avanti to 2 meters. On the left a simple antenna uncharged upper right has
placed a mirror, using this analogy to show how the top tube length is extended. This is about the effect of
the cross (top load) Astroplane Avanti antenna for purposes of radio waves form a mirror which extends
above.
Figure 4. Analogy of elongation of an antenna by higher load.
The antenna patented in 1971 is shown in Figure 5, consists of an upper 1/8 wavelength, at the end of which
a load is placed on cross-shaped elements 4 made up of 1/16 of length wave.
The middle part of the antenna elements consists of two 1/4 wavelength that is separated height diminishes
progressively as to join a ring 1/16 wavelength in diameter.
The upper 1/8 wave joins one of the means of 1/4 wavelength.
Additionally a support mast, which is part of the antenna should be placed on the feeding point, together with
the junction between the upper and middle section. It is at this point that connects the shield (mesh) of the
coax that feeds power to the antenna. The center of the coax is connected to the end means not connected
to the upper element.
Figure 5. Avanti patented antenna
The dimensions of the antenna to be marketed is shown in Figure 6.
Figure 6. Avanti antenna measures factory Astroplane
We plotted using software Avanti 4nec2 antenna with the dimensions proposed the manufacturer's manual
was obtained frequency response shown in Figure 7.
Figure 7. frequency response of the antenna manufactured Avanti Astroplane
Note that the best response is obtained around 24.8 MHz with an approximate bandwidth VSWR 2, 24.75 to
26.25 MHz, ie about 1.5 MHz
It should be noted that while the digital model we have implemented measures of the items listed in the
owner's manual, the truth is that in reality the dimensions are slightly lower for the fact that connecting each
of them loses a bit of its length.
Under this outcome, indeed unsatisfactory, because the frequency is centered outside our band of interest
(27.4 MHz) have undertaken to optimize the dimensions.
The frequency response of the optimized dimensions shown in Figure 8.
Figure 8. Frequency response of elements with dimensions optimized
It shows a response centered at 27.5 MHz with a bandwidth of VSWR of 1.5 at 1 MHz With a VSWR of 2 the
bandwidth is about 1.5 MHz
The owner's manual says that the antenna has full coverage in the 40 CB channels and so our Avanti
Astroplane 1VSWR optmizada to 1.5, covers 26.8 to 27.9 MHz
Can you change the bandwidth?
The answer is YES.
You can change the bandwidth of the Avanti Astroplane. The antenna Avanti Astroplane respond in a
frequency range higher in proportion to alarge element holding the cross, which I call top element.
If the top element is bigger then continued imposition of the antenna to resonance, the cross should be
smaller.
Remember that the cross is simply a mirror to complete the electrical quarter wave should be the top item.
SI extiede reaching the upper quarter wave, then the cross disappears.
And this is where I would further simplification, if you suppress the cross, by the elongation of the top up to
1/4 wave antenna J then we have a 1/2 wave with a circular element in the base.
Setting the Avanti Astroplane:
We found that by adjusting the size of the cross is set the resonance frequency, as expected.
Some colleagues have raised, but did not try it, this can also be achieved by telescoping the upper element
to change its size and therefore its resonant frequency without changing the size of the cross.
Furthermore, when adjusting the resonance frequency indicated by the process also changes the
impedance, so that the adjustment should be completed by opening or closing the elements of the middle
section. This is achieved very easily if there is the insulating spacer of the middle section upwards or
downwards. See Figure 6, there the insulator is called "fiberglass rod".
You need to clarify something, there are two parameters that deal if you decide to build this antenna, one is
the impedance and the other is the resonance.
An antenna is resonant when its dimensions are related to multiples or fractions of a wavelength. When this
occurs, the antenna is able to capture most signals when their size is such that it is in resonance.
The antennas operate more efficiently then the extent that their size is related to the wavelength, either by
multiples or submultiples.
Now, Avanti and generally any antenna may be in resonance, but its impedance be incorrect. If this occurs
will see that the antenna responds well in a frequency range including the stationary tend to lower the
resonance frequency, but will not fall enough. This is the case with colleagues who encounter cases where
the antenna could not lose eg 2.0 VSWR.
In the case of the antenna Avanti, if adjusting the length of the cross elements or upper element, you get a
"dip" (minimum) of stationary center frequency around which want to cover the range, then tries to adjust
the separation of the two media elements by adjusting upwards or downwards the insulating spacer
element, this also affects the impedance and resonant frequency, but then can return to the adjustment of
the upper cross member or to recover the desired frequency.
Irradiation patterns
Figure 9 shows the vertical radiation pattern of the antenna Avanti Astroplane in free space. Figure 10 shows
the same graph, as filed by the inventor to apply for a patent.
Figure 9. Antenna radiation pattern Avanti vertical Astroplane
The simulation shows a peak gain of 1.53 dBi in the direction of 10 degrees above the horizon (80 degrees in
the graph of figure 9) in the release space.
Figure 10.Patrón Avanti Vertical Antenna Astroplane irradiation (Patent)
Figure 11 shows the vertical pattern in the presence of an actual ground, note the maximum irradiation angle
of 0 degrees to the horizontal and a gain of 12.7 dBi.
Under the "owner's manual" for this antenna, the AV101 model, indicates you have a gain of 4.46 dBi. But
remember that means dBi gain with respect to isotropic irradiator, a nonexistent antenna (theoretical) used
to mathematically determine the antenna gain.
A half-wave dipole antenna is 2.15 dBi, what is known as 0 dBd. So Astroplane Avanti antenna is 4.46 - 2.15
= 2.31 dBd. Or what is the same, has a gain Astroplane Avanti actual manufacturer under 2.31 dB over a
dipole.
Figure 11. Avanti Astroplane on royal land
But Figure 11 shows a simulation result gain of 7.12 dBi digital, ie is a gain of 7.12-2.15 = 4.97 dBd. This
coincides with the proposal of the manufacturer.
The power supply (Connecting you coaxial cable to the antenna)
In the patented design Martino (see patent reference) is fed into the power element short. See figure 12.
Figure 12. Feeding power
As seen in Figure 12, are installed at two metal sheets screwed to one another, embrace the antenna tubes.
As shown in Figure 13 brass clamp (orange in the figure) is welded at the center of the connector PL. This
bracket is C-shaped, ie it is a cylinder having a groove on one side, so when the rubber blocks which are
pressed by the pressing sheet metal is brass clamp, binds strongly to aluminum stub.
Figure 13. Detail of the power supply
An Avanti for 2 meters
Using the measures provided by the calculation program located in the antenna section of this page (see
Figure 14) was constructed Astroplane Avanti antenna for 2 meters, centered at 146 MHz The finished
antenna shown in Figures 15, 16 and 17.
Figure 14. Avanti antenna for 2 meters "Avanti antennas calculator"
This program was developed using Microsoft Silverlight technology to be implemented directly in the browser
without downloading. For this reason, requires installed in your browser component free Microsoft
"Silverlight". If you do not know if you have it installed or not, simply go to the calculator page, if necessary
instalr the Microsoft, an icon that will guide DIRECTLY from the Microsoft server.
Figure 15. Avanti antenna for 2 meters
Figure 16. Antenna installed at 2 meters above the ground
Figure 17. Power supply in the prototype of 2 meters
The input impedance
Astroplane Avanti antenna has an input impedance of about 60 ohms, as shown in Figure 18 for the case in
modeling 4nec2 27 MHz.
Figure 18. Real part of the impedance of an antenna Avanti Astroplane
The avanti "antenna deaf?"
As I stated above, avanti has two operation modes, one in which the impedance of the antenna feed point is
close to 50 ohms (which can be achieved by opening or closing means of the antenna elements "dress the
dancer "), ie in which the VSWR is low and the other, in which the antenna is in resonance or not (that is
achieved with the size of the cross or" top load ")
The avanti not necessarily be in resonance for low VSWR!, And ANY this antenna is in resonance when its
dimensions are related to multiples or fractions of the wavelength, only in these conditions produces
maximum power transfer waves traversing the antenna to the receiver.
Put another way, our thesis is that an antenna is more efficient, or "hears" inasmuch as it is in resonance. Ie
repeat, in so far as its dimensions are related to a multiple or submultiple of a wavelength. And remember
that the wavelength in the aluminum or copper is not the same as in air, something called speed factor, ie
because the wave travels slower in other material, in relation to its speed in air. But also remember that all
elements tip ending in a phenomenon manifests shortening for radio waves in relation to the wavelength,
which is known as edge effect.
So 300 divided by the frequency in MHz is a wavelength in air, but not necessarily in an aluminum tube or a
copper wire.
Furthermore, some colleagues do not take into account that the diameter of the elements has a direct
relationship with the end result, because the physical dimensions change in the antenna, all this analysis is
given diameters referred to by the inventor of the antenna, which shown in Figure 6. Therefore, a
recommendation: If you manufacture an antenna for another frequency Avanti (other than the band of 11
meters) take into account the transfer tube diameters in the proportion stored in the pattern shown in Figure
6 for the 11 meter band.
A few days ago Ti2MAB joked, Mario and T4VZ Victor in regard to good theory, could be transmitted using an
antenna in which the bed rests, "the metal bed" as we say the Ticos, if using a suitable coupling that
transforms the impedance of "cot" to 50 ohms. But that does not mean it would be an efficient transmission
system. But watch out, it could also be argued that "the cots do not work as antennas that are very poor,"
actually, oddly humorous, if fitted properly and similar measures are resonant, its efficiency would certainly
enviable :)
Therefore, it seems unfair that some colleagues, with many experience but little knowledge, avanti claim
that the antenna is deaf.
I have to confess that I built Avanti antenna to test the calculator avanti antennas described above, gave me
such good results, it is my job to regularly communicated on 2 meters, and do not consider ANYTHING DEAF.
Lightning Safety
Astroplane Avanti antenna is an antenna that has all the grounded structure, and which offers a considerable
advantage in terms of security on other antennas that operate in isolation, such as the antenna ground
plane, "umbrella" or "leg de gallo ", in which the vertical element, the most exposed to the thunderstorm, is
isolated from ground and is directly connected to your computer, in your home ..
One final note: Is the Avanti Astroplane the best antenna?
The answer is a resounding no, the best antenna there.
It exists because the term "best" is very subjective, what makes you believe in an antenna as "the best" is
not necessarily what everyone would. I mean the term has many meanings. One who is interested in the dx
can search the best directional antenna, but maybe another directivity considered as a disadvantage
because they are interested in the local comunidados, so we attract more omnidierccional antenna.
Even within the same type of antennas, omnidirectional for example, could difererir what features would
make the best antenna, if the beam angle low or high; completely grounded structure, the size, the power
capacity, etc..
Each antenna has its merits, it is only fair to say, for example, in terms of some specific feature compared to
other antenna if your interest is favorable or not. But never generalize. I argue that the Avanti I can
Astroplane, in theory has more gain than the Sirius 827. The Avanti is 2.31 dBd and only 1.5 dBd 827 Sirius.
The manufacturers say in their user manuals. But a little search on google so can confirm.
I can also state that both antennas being the same height and at the same point, the antenna is reported
Astroplane Avanti more signal relative to the Sirius 827 (9 units of Avanti, the Syrian 8 Units 827). But in
terms of handling high power as 2 or 3 KW, maybe Sirius is superior.
But why would you buy for more than 100,000 colones lower gain antenna (The Sirius 827) if less than 20,000
to build an Avanti Astroplane (high gain) can not handle 2 KW perhaps, but that does not even account when
operating at 5 or 20 watts that has his team (which is the legal limit of course).
Also consider that when you refer to an antenna, you must provide numbers, many esteemed colleagues
used as the sole argument for some antennas, such as the Sirius 827, the trite argument "Install this super
antenna and now I will" clear , but what about if not convinced? who gives back to you the most and 100,000
colones you paid for the super antenna?
I do not think either that it is factory antenna is better than another type home. The antennas follow
mechanical and electrical principles which can satisfy both the amateur as professional buildings in factories.
Do not fall into the trap of many traders who just want to sell, after all, what is ham radio but
experimentation?
. Collaborations in creating this article
My thanks to Ti5WLR, Wilberth and Ti2UNA, Gerardo for his help and advice in connection with this antenna.
So our thanks to Henry, "Renegade" San Isidro de Grecia, Costa Rica, experimentation and comparative
testing of Avanti Astroplane of 2.31 dBd (described here) with the Sirius antenna 827, which was evident in
the practice, the superiority in signal reported already in theory offers the Avanti Astroplane on that just 1.5
dBd antenna.
Comments and inquiries:
If you want to share your comments, photo or experience with this antenna send an email to
[email protected], we would appreciate it.
References:
1. Google patents website.
2. 26 alpha tango UK site (pdf)
3. Huang Yi / Kevin Boyle. Antennas from theory to practice. Editorial Willey. United Kindom 2008.
4. The ARRL Antenna Book. 19th Edition. ARRL CT, USA. 2000.
5. Edmund Laport. Antennas Engineering. McGraw Hill. Buenos Aires, Argentina.1963.
6.Digital Antenna Modeling 4Nec2.
Files available for download:
1. Model created by Ti5LX ASTROPLANE AVANTI antenna for 4nec2 software (download requires 4nec2).
Permission to use the information contained on this page if you specify the source of it.
United States Patent I 113,587,109
72) Inventors Louis J. Martino (56) References Cited
343 N. Craig Place, Lombard, Ill. 60148; UNITED STATES PATENTS
Herbert R. Blaese, Chicago, Ill.
21 ) Appl. No. 779,942 2,118,396 5? 1938 Davis et al.................... 343/874
22 Filed Nov. 29, 1968 2, 184,729 12/1939 Bailey........ 343/830
45 Patented June 22, 1971 3,103,638 9, 1963 Greuet......................... 333,125 X
73 Assignee said Martino, by said Blaese Primary Examiner-Eli Lieberman
Assistant Examiner-Paul L. Gensler
Attorney-Dressler, Goldsmith, Clement and Gordon
ABSTRACT: A communications antenna which includes a
(54) OMNIDIRECTIONAL COMMUNICATIONS vertical conductive mast and a pair of one-quarter wave length
ANTENNA HAVING CAPACTIVELY LOADED TOP conductors extending downwardly from a first reference level
14 Claims, 8 Drawing Figs. to a second reference level. The conductors are electrically
connected at the second reference level and one of the con
52 U.S.C. ....................................................... 3437792, ductors is electrically connected to the mast at the first
3431830, 3431899 reference level. A one-eighth wavelength conductor extends
51 int. Cl......................................................... H01q9/16 upwardly from the first reference level and is electrically con
50 Field of Search............................................ 343/790 nected to the mast at the first reference level. The one-eighth
-792, 828-831, 890,908, 899, 843, 874; wavelength conductor is capacitively loaded at its top to act as
333/25, 26 a one-quarter wavelength conductor.
is
PATENTED JUN22197 3,587, l OQ
SHEET 1 OF 2
FIG. fa PRIOR ART
WS
as & N
NM no
N O SN
&&
/NVENTORS
2érbert *f; 2 ZC.Y.J E.
Offorties
PATENTED JUN22197 3,587, l09
SHEET 2 OF 2
67%72et?, Alcese
CE
auts-Ee 2.
E2,223
Georvezas
3,587, 109
2
OMNIDIRECTIONAL COMMUNICATIONS ANTENNA jects is frequently encountered substantially reducing the
signal strength of such an antenna.
HAVING CAPACTIVELY LOADED TOP A comparable environmental showing of an antenna 12 of
This invention relates to antennas, and more particularly to this invention in use is pictorially illustrated in FIG. b. There
omnidirectional communications antennas which are espe it can be observed that maximum signal strength is developed
cially useful for citizens band applications. at and near the top of the antenna and with a lower takeoff
Present Federal Communications Commission regulations angle assuring maximum signal power (within legal limits on
limit the height of citizens band antennas to 20 feet above the height) over nearby ground supported objects such as
highest tip of one's property, and require direct line of sight
radiation (with minimal ionosphere reflection). Prior art an 10 buildings, power lines, trees and difficult terrain that would in
tennas for citizens band use generally comprise a one-half terfere with or block performance of ordinary antennas.
wavelength or five-eighth wavelength monopole which is Because the maximum height of certain classes of antennas is
loaded at the bottom. Because of such loading, prior art anten restricted by law and governmental regulation, the provision
nas of that type produce maximum current in the lower por of an antenna having the capacity to provide radiation from its
tion of the antenna, and, therefore, such antennas effectively 15 upper portion is highly advantageous, particularly when the
takeoff angle of the signal is low.
radiate from their lower portions. It has been found that a Referring now to a first embodiment of an antenna of this
citizens band antenna can be made which does not exceed the invention and to FIG. 2, antenna 12 comprises a first conduc
legal height limitation but which effectively radiates from its tor 4. As there illustrated, first conductor 4 is a vertical
upper portion. This is extremely advantageous because it al boom member
leviates the problem of shadow caused by houses and other 20 elongate secondor mast which and an elongate third conduc
conductor 16
is electrically conductive. An
ground supported objects which may be located near such an tor 18 are positioned on opposite sides of conductor 14 and
antenna and which would otherwise tend to block its transmis extend vertically downwardly generally from a first horizontal
sion and reception paths.
Tests on the antenna of one embodiment of the present in 25 plane or level A16 and 18 are equidistantly spaced from level
B. Conductors
to a second parallel horizontal plane or
first
vention have shown, among other things, that its construction conductor 14 and are oppositely positioned. They lie generally
provides a radiation pattern that is lower than the radiation along a surface of revolution about first conductor 14 and
pattern of prior art antennas. This, therefore, reduces scatter flare downwardly and outwardly from level A to level B in
and produces higher gain. In use, the antenna of this invention
yields a signal received at distant points that is stronger than 30 prises alies a fourth loop encircling first conductor 14. Fourth
which
conductive
conductor 20 which as illustrated com
the signal received using prior art antennas under identical conductor 20 mechanically and electrically interconnects
conditions and at the same location. This and other ad
vantages result from the practice of the instant invention. conductors 16 and 18, as by sheet metal screws or nuts and
bolts (not shown).
In accordance with this invention there is provided a com
munications antenna having a variety of uses, but which has 35 meansposition conductors 14,end a 18 and assembly 24 is pro
To
are provided. To that
16,
clamp
20, other fastening
special application for citizens band (CB) use. The antenna of vided at level A. Clamp assembly 24 comprises a pair of
the illustrative embodiments of the invention comprises a ver clamping elements 25 which grip the ends of conductors 16
tical first conductor and a pair of conductor members on op and 18 and which mount U-bolt 26 for anchorage of boom
posite sides of the first conductor and extending between
parallel first and second horizontal levels. The first conductor 40 define an14 thereto. The complementary clamping16, and a
member
end portion 28 for retaining conductor
elements
terminates at the uppermost level and projects downwardly
below the second level, the latter preferably a distance at least second end portion 30 forend portion 30 comprises As shown
in greater detail in FIG. 4,
retaining conductor 18.
insulative
equal to the distance between the levels. The pair of conduc bushing means or bushing segments 34 and a split brass ring
tor members are electrically connected at the lower level, and
one of the conductor members is electrically connected at the 45 ductor 18. is provided for encircling and contacting the con
36. Ring 36
upper level to the first conductor and to a projecting conduc A coaxial transmission means or cable 37 runs up the verti
tor which extends upwardly from that upper level. The pro cal boom to level A and terminates in a coaxial connector 39
jecting conductor has an effective electrical length equal to secured to the clamp assembly. A first transmission feed lead
the length of the conductor members. Transmission or feed 50 38 of cable 37, its braided cover, is electrically connected to
leads are provided at the upper level.
A more detailed explanation of the invention and of its ad clamping element 25ring 36 (hencelead 40third conductor 18
nected to split brass
and the inner
to the
is electrically con
vantages is provided in the following description and is illus at level A). The third conductor 8 is insulated from the first
trated in the accompanying drawings, in which: and second conductors at level A at which the clamp assembly
FIG. Ia is a pictorial elevational view of a conventional 55 24 lies by insulative segments 34. Four bolts and nuts 42 are
prior art antenna in actual use; provided adjacent end portion 30 to compress segments 34 of
FIG. 1b is an elevational view, similar to the view of FIG. 1a, the insulative bushing against each other to cause the split ring
showing in use an antenna according to the principles of the to engage conductor 18 tightly and to provide a secure electri
present invention; cal connection there between and at level A.
FIG. 2 is a front elevational view of an antenna constructed 60 End portion 28 is configured to clamp directly to conductor
in accordance with the principles of the present invention; 16, thereby to electrically connect the first and second con
FIG. 3 is a fragmentary perspective view of a portion of the ductors, 14 and 16, at level A. Four further nuts and bolts 42
antenna of FIG. 2;
FIG. 4 is a fragmentary top plan view of a portion of the an are provided to anchor conductor 16 to the antenna assembly.
tenna illustrated in FIGS. 2 and 3; Because U-bolt 26 firmly anchors and electrically connects
FIG. 5 is a schematic diagram of the antenna of FIG. 2;
65 vertical boom 14 to clamp assembly 24, it will be apparent
FIG. 6 is a schematic diagram of a modified antenna accord that clamp assembly 24 serves as a fifth conductor at level A.
ing to a second embodiment of the present invention; and Mechanically, it is also clear that U-bolt 26 firmly anchors
FIG. 7 is a polar diagram showing the radiation charac clamp assembly 24 and vertical boom 14 at level A so that all
teristics of an antenna of FIG. 2. of conductors 14, 16 and 18 are firmly interconnected
70 mechanically at level or plane A.
A typical prior art antenna is pictorially illustrated in FIG. To aid in providing the aforementioned flare for conductors
1a. In such an ordinary collinear or ground plane antenna 10, 16 and 18, the conductors are secured to the first conductor
radiation is spread near the junction of the radials and the ver 14 by a suitable insulating spreader clamp 22. Spreader clamp
tical member at the base and little radiation is effected at the assembly 22 is preferably of fiberglass but may take any other
top of the antenna. Accordingly, interference from nearby ob 75 form which will serve to insulate conductors 14, 16 and 18
3,587, 109
3 4.
from each other thereat. A suitable spreader clamp assembly tain uses, such a downward tilt may be desirable, it appears
is pictorially illustrated in FIG. 2 and is shown in greater detail that the optimum disposition of conductors 16 and 18 lies
in FIG. 3 to include a clamp band 45 surrounding vertical between the parallel positioning of straight conductors 16 and
boom 14 and a fiberglass bar 41 secured thereto, the ends of 18 and the flared positioning of flared conductors 16 and 18
which bar are mechanically secured as by loop clamps 43 to with respect to the conductor 14, as described in conjunction
the conductors 16 and 18. The length of the bar arms and the with the specific embodiment illustrated in the drawings.
point of interconnection therealong to the conductors will The electrical circuit of the antenna of FIG. 2 is illustrated
determine the amount of flare of conductors 16 and 18 schematically in FIG. 5. Dimensions a and b are each one
between levels A and B. fourth wavelength in electrical length, although, as stated
A sixth conductor 46 projects upwardly from level A and O
above, conductor 46 may be actually shortened by capacitive
clamp assembly 24. In the embodiment of FIGS. 2 and 3, con ly loading the antenna at its top. Of course, with a citizens
ductor 46 comprises a one-fourth wavelength assemblage, a band antenna a shorter portion 47 effectively raises the signal
straight vertically projecting component of which is integrally pattern beyond that obtained with prior art CB antennas. The
formed with second conductor 16. The upwardly extending in 15 coaxial cable connections at level A are illustrated as being at
tegral component 47 is one-eighth wavelength in length (one points c and d.
half the length of conductors 16 and 18) and is topped by It will be noted that conductors 18, 20, 16 and 24 define an
capacitive loading means such as a transverse conductor open conductive loop having opposite side sections compris
means which is illustrated as crossed conductors 48 and 50, ing conductors 16, 18 and a loop segment or loop portion
which in the illustrated embodiment are about one-eighth 20 comprising conductor 20 electrically connecting the ends of
wavelength long. Crossed conductors 48 and 50 are anchored the side sections at level or plane B. In that construction the
as by threaded fastening means to the end of portion 47 to in conductive loop is fed by a first transmission lead or feed
tegrate the antenna assembly and to connect portion 47 and means adjacent the intersections of one side section of the
crossed conductors 48 and 50 to each other electrically and conductive loop, the vertically projecting conductor and the
mechanically. By utilizing a one-eighth wavelength portion 47 25 first conductor, and by a second lead means to the other side
with crossed conductors one-eighth wavelength long, an effec section at plane A. A construction wherein points c and d are
tive one-fourth wavelength projecting antenna portion is ob electrically coupled, but where the circuitry is otherwise
tained above level A. Because principal radiation occurs similar, will produce a similar result, i.e., a closed conductive
between level B and the level of the crossed conductors, if a loop may also be used.
larger band width is desired, portion 47 may be increased in 30 A modified antenna construction is shown in FIG. 6, in
length and crossed conductors 48 and 50 reduced in length or which a "prime' is added to corresponding reference nu
eliminated to give the same effective wavelength, i.e., one merals. In the embodiment of FIG. 6, the sixth conductor 46'
fourth wavelength. is an integral extension of the vertical boom 14" rather than of
The antenna illustrated in FIGS. 2-5 is shown to be verti conductor 16 as illustrated in FIGS. 2-5.
cally oriented which for many uses is the most desirable, for 35 in the embodiment of FIG. 6 the clamp assembly 24' electri
example for CB use. However, it is clear that is may be cally connects conductor 16' to conductor or mast 14' at level
horizontally oriented and may, therefore, be supported by a A. It is preferred that conductor 46', which extends upwardly
horizontal boom member rather than the vertical boom from base clamp 24', be one-eighth wavelength long and be
member or mast 14. In such a construction the horizontal loaded at the top with crossed conductors to form the
planes or levels A and B would then be vertical parallel planes 40 equivalent of a one-fourth wavelength monopole above the
or levels. base clamp 24' as described previously. The coaxial cable
Although in normal use the boom member 14 will be quite connections c' and d" are comparable to those of FIG. 5.
long, it has been found that the takeoff angle of the signal at Dimensions a' and b' are each one-fourth wavelength in elec
maximum strength tilts upwardly more as the first conductor 45 trical length in the embodiment of FIG. 6, as with the embodi
14 decreases in length from one-half of the wavelength on ment of FEG. S.
which the antenna is intended to operate. Stated another way, The antenna of the present invention has been found to be
the first conductor 14 should preferably project beyond level particularly useful in citizens band operation at about 27
B a distance at least equal to about the length of conductors 29.7 megahertz. It is to be understood, however, that the an
16 and 18. When the length of the first conductor 14 is so 50 tenna may be used at other frequencies, for both propagation
dimensioned, the takeoff angle at maximum signal strength is and reception. Maximum signal strength is at the top portion
optimized for such as CB use and the like. It will be apparent, of the antenna, as contrasted with prior art antennas in which
however, that where a steeper takeoff angle at maximum the maximum signal strength is well below the maximum legal
strength is to be desired in other environments, the length of height. As a result, maximum signal power can be transmitted
conductor 14 may be reduced. and received over nearby buildings which would normally
It will be observed that conductors 16 and 18 flare out 55 block and interfere with the transmission and reception of
wardly and downwardly. Their relative diameters and the prior art antennas.
spacing of them from each other and from the mast, as well as Performance tests on the FIGS. 2-5 antenna have shown
the flare, controls the impedance at c, d (FIG. 5). This im that the antenna produces radiation at a low angle and with a
pedance preferably is 50 ohms in accordance with the typical 60 relatively narrow lobe, thereby concentrating the signal at a
construction described and for CB use. However, the diame more useful angle and level resulting in improved higher
ters of the parts, the spacing and the flare may be varied to ob received signal level.
tain either different impedances or the same impedance via Indeed the antenna construction substantially counteracts
variance of diameters, spacing and flare in a manner that will the tendency of prior art antennas to tilt the radiated signals
be understood by those skilled in the art for the antenna to 65 substantially upwardly. A polar diagram showing the radiation
operate most efficiently. characteristics of the antenna of FIG. 2 is shown in FIG. 7.
It has been found, however, that the flare affects not only Performance tests resulting in the diagram of FIG. 7 were
the impedance, but also influences the takeoff angle at max run. For one such test, an antenna scaled down to propor
imum signal strength. The flare of the construction described tionate wavelength dimensions for operation at 146 megahertz
hereinafter provides a takeoff angle that is about the max 70 was prepared. Thus the first conductor or mast 14 was 33.5
imum reasonably allowable for most efficient CB use of this inches in length. The distance between levels A and B was
antenna. When the flare was omitted and the conductors 16 17.75 inches and the conductor 46 (unloaded) was 15.75
and 18 were tested parallel to the first conductor 14 it was inches. Conductors 16 and 18 flared outwardly as described
found that the takeoff angle at maximum signal strength was herein. The pattern was measured at a distance of about 100
as much as 10 to 15° below the horizontal. Although for cer 75 feet from the antenna.
3,587, 109
S 6
It is seen that the beam at maximum strength is tilted up of the conductors 16 and 8 is very slightly under one-quarter
wardly from horizontal only about 5° and that the radiation wave length in length at 29.7 megahertz. The antenna, there
pattern lobes are of an optimum shape. fore, operates most efficiently and effectively at that frequen
In other tests of the same installation, but with shorter mast cy. It has been determined that the antenna described herein,
lengths of 21.5 inches, 24.5 inches and 27.5 inches it was wherein the one-quarter wavelength components are 8 feet
found that the radiation angle at maximum beam strength long, operates efficiently and satisfactorily within the 27
tilted upwardly substantially more. The conclusion to be 29.7 megahertz range demonstrating that the antenna is effec
drawn, therefore, was that a mast having a length below level tive where the quarter wavelength components approximate
B of about one-quarter wavelength, i.e., about the length of one-quarter wavelength in electrical length. This is especially
the conductors 16, 18 gave an optimum takeoff angle. 10
so when the conductor 46 is one-quarter wavelength, for the
A typical antenna now being made and marketed in ac efficiency drops somewhat for a broader band when the con
cordance with the principles of this invention is adapted to be ductor 46 is capacitively loaded, as by the crossed conductors
mounted to a mast 14 which may be a 20-foot steel or alu 48 and 56.
minum mast and which may be 1 % inches in diameter. A 4 5 An antenna constructed in accordance with the specific em
foot section of one-half inch aluminum tubing which is flat at bodiment just described is 12 feet in length (except for the
one end is provided with four 2-foot radial aluminum tube mast which desirably extends at least about 8 feet below level
members each of which is three-eighth inch in diameter. Each B) and weights about 3% pounds. It is omnidirectional and has
is flattened at one end and bored to facilitate securance to the an impedance of 50 ohms, a power gain of about 4 db. over
4-foot section and to project radially therefrom to constitute 20 the isotropic radiator, will operate on powers of several
conductor 46. The 4-foot section comprises conductor com kilowatts, is vertically polarized, is effective on a frequency
ponent or portion 47 and pairs of the 2-foot sections comprise band of 27-29.7 megahertz for such as CB use, and is par
the transverse component or crossed conductors 48, 50. ticularly effective within that entire range when crossed con
A pair of clamping elements 25 of aluminum are provided. ductors 48 and 50 are omitted and conductor 46 comprises a
Two 8-foot sections of one-half inch diameter aluminum tub 25 projecting conductor element 47 about one-quarter
ing are positioned in the end portions 28, 30, one of the two 8 wavelength in length. It will be apparent that antennas of other
foot sections (conductor 16) being proportioned to receive physical sizes proportioned to the wavelength of other
the end of conductor portion 47 at the clamp members and in frequencies may also be constructed in accordance with this
end portion 28. Each of the 8-foot sections is fabricated from invention as well. It has a standing wave ratio (pretuned) of
a pair of 4-foot sections of tubing which sections are secured 30 less than 1.4:1 on 23 CB channels.
to each other at adjacent ends. These 8-foot sections then lt is to be understood that the embodiments of the invention
comprise conductors 16 and 18 and are clamped in end por that have been shown and described are merely illustrative,
tions 28 and 30 constructed as described previously. From and that various substitutions and modifications may be ef
center-to-center, conductors 16 and 18 in end portions 28, 30 fected by those skilled in the art without departing from the
are spaced apart approximately 6 inches. At the time conduc 35 spirit and scope of the novel concept and principles of the in
tors 16 and 18 are clamped in the clamp assembly 24, conduc vention. The principles of the present invention are applicable
tor 46 is secured to the clamp assembly and made electrically to antennas utilized for both the reception and propagation of
integral with conductor 16. electromagnetic energy. Further, the scope of the invention is
Next, two pairs of three-eighth inch aluminum tubing each not intended to be limited by any described frequency range
piece being bent to a 90° arc are secured to each other by 40 or theory of operation.
fasteners and by loop clamps and to the lower ends (level B) What we claim is:
of the 8-foot sections 16 and 18. This then provides a circular ... In a communications antenna having a first vertical con
loop segment electrically connecting the lower ends of con ductor, a pair of spaced apart conducting members suspended
ductors 6, 18 to each other and at a distance of about 30 at their tops from said vertical conductor on opposite sides of
inches center-to-center. Intermediate their lengths, i.e., at the 45
4-foot point, sections 16 and 18 are provided with a spreader said vertical conductor, said conducting members extending
downwardly from a first horizontal level at their tops to a
clamp assembly 22 which includes a fiberglass rod 41 approx second horizontal level at their bottoms, said pair of conduct
imately 13 inches in length and three-eighth inch in diameter. ing members being equal in length, means electrically con
This is secured to mast 14 by a stainless steel loop clamp 39 50 necting the bottoms of said pair of conducting members, a ver
and to each of conductors 16 and 18 by loop clamps 43. From tical conducting element electrically connected to one of said
center-to-center, conductors 16 and 18 are each spaced apart pair of conducting members and extending vertically up
about 12 inches center-to-center on opposite sides of mast 14. wardly from said first horizontal level and to an elevation
Of course, prior to securing the fiber glass rod to the mast, a equal to at least one-half the length of each of said conducting
U-bolt clamp 26 is positioned about the mast at the clamp as 55 members, and transmission leads, one of which is electrically
sembly 24 to mount the antenna to the mast. Thereafter the connected to said vertical conductor at said first level and to
fiber glass rod is secured to the mast. The clamping and pro the top of the conducting member to which said vertical con
portioning provides a significant flare of the conductors 16, ducting element is electrically connected and a second of
18, which as previously described, influences both takeoff which is electrically connected to the other of said conducting
angle and impedance. The takeoff angle and impedance may 60 members at the first horizontal level.
be varied or altered, as described hereinbefore. 2. In the antenna of claim 1 in which said vertical conduct
Of course, as explained, coaxial cable feed connections 38 ing element comprises a vertical component about one-half
and 40 are made to the clamp assembly and to the split brass the length of each of said conducting members and a horizon
ring and the cable 37 itself is suitably taped to the mast. It has tal component having a horizontal extent of about one-half the
been found that when an outer braided conductor forms the 65 length of each of said conducting members.
cover of the coaxial cable, this may serve as the first conduc 3. In a communications antenna; a first conducting element
tor. In such a case, the conductive mast 14 may be omitted projecting in a first direction from a first reference plane
and a nonconductive support substituted therefore. When that towards a second parallel reference plane, a pair of spaced
is done, it is important to make certain that the coaxial cable is apart elongate conducting members each supported at one of
positioned and centered properly with respect to the other 70 their respective ends on said conducting element and spaced
conductor members described. substantially equidistantly from said conducting element, said
By way of summary, conductors 16 and 18 are each about 8 conducting members extending from said first reference plane
feet long, conductor portion 47 is about 4 feet long, conduc at their said one ends to said second generally parallel
tors 48, 50 are each about 4 feet long, and conductor 20 is ap reference plane at their other ends, said pair of conducting
proximately 8 feet in circumference. It is to be noted that each 75 members being substantially equal in length, means electri
7
3,587,109
8
cally connecting the said other ends of said pair of conducting tion, at least one of said side sections being electrically cou
members to each other, a projecting conductor electrically pled to said conducting element at said first plane, said loop
connected at said first reference plane to one of said pair of segment electrically connecting the other ends of said pair of
conducting members and extending in the direction away side sections at said second plane, a projecting conductor
from said second reference plane a distance from said first electrically connected to said one side section and extending
reference plane that is equal to at least about one-half the
length of said conducting members, and transmission lead from said first plane away from said second plane a distance
means, one of which is electrically connected to said conduct equal to at least about one-half the length of each of said side
ing element at said first plane and to the said one end of said sections, and transmission lead means comprising a first lead
one conducting member to which said projecting conductor is 10 electrically coupled to said conducting element, the conduc
electrically connected, and the other of which is electrically second lead connected to the other of said sidefirst plane, and a
tive loop and the projecting conductor in said
sections.
connected to the other of said conducting members.
9. In the communications antenna of claim 8, wherein the
4. In the antenna of claim 3 in which said first conducting conductive loop is an open loop.
element extends beyond said second reference plane a
distance at least equal to about the distance between said first 15 10. In the communications antenna of claim 8, wherein the
and second planes. first conducting element is straight and said conductive loop
5. In the antenna of claim 3 in which said projecting con side sections lie along a surface of revolution generated about
ductor comprises a straight section about one-half the length the axis of said first conducting element.
of said conducting members and capacitive loading means at 11. In the communications antenna of claim 8, wherein said
the free end of said projecting conductor. 20 plane. lead is connected to said other side section at said first
second
6. In the antenna of claim 3 in which said first conducting
element is vertically oriented, and further embodying means 12. In the communications antenna of claim 8, wherein said
for supporting said antenna in a vertical orientation. first conducting element is vertically oriented and comprises
7. In the antenna of claim 6 in which said first conducting an electrically conductive boom member extending below said
element and said means for supporting said antenna in a verti 25 second plane a distance equal to at least about the lengths of
cal position are integrally formed as an electrically conductive said side sections.
elongate vertical boom member. 13. In the communications antenna of claim 8, wherein said
8. In a communications antenna comprising a first elongate side sections are generally concentric about a straight first
conducting element projecting from a first reference plane conducting element and flare outwardly of said first conduct
toward a second parallel reference plane, a conductive loop 30 ing element from said first plane to said second plane.
generally parallel to said elongate conducting element and in 14. In the communications antenna of claim 8, wherein said
cluding opposite side sections disposed on opposite sides of first conducting element is straight and said side sections are
said conducting element and a loop segment, said side sections substantially straight and substantially equidistantly and op
extending between said first plane at one end of each side sec positely spaced from said first conducting element.
tion and said second plane at the other end of each side sec 35
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