Multi-Band Vertical Antenna

1. Field of the Invention

The present invention relates generally to an antenna, and more particularly, pertains to a high frequency vertical antenna.

2. Description of the Prior Art

Those concerned with antennas have long recognized the need for a high frequency vertical antenna including automatic band switching. The present invention fulfills this need.

The traditional prior art vertical antennas have relied on anti-resonant inductor-capacitor circuit traps placed at or near the quarter-wave current antinode points to decouple varying lengths of the available radiating structure on those bands where the total height of the vertical antenna was greater than an electrical quarter wavelength. The approach provided that the overall height of the radiating structure was typically less than a quarter wavelength at the lowest frequency of operation and the exact height was largely determined by the inductance-capacitance ratio of the traps. The usual method to provide eighty meter resonance in vertical antennas was to utilize a high inductance coil at the top of the structure which simultaneously served as a forty meter decoupling trap and as a loading for eighty meter resonance. In most designs, additional loading in the form of capacity hats was used to limit the overall height of the structure to something less than one-eighth wavelength on the lowest frequency. The physical height of the active radiating sections was usually less than a quarter wavelength because of the inductive reactance of the several decoupling traps at frequencies below the frequencies which the decoupling traps were tuned.

The prior art vertical antennas have had a number of limitations. First, the active antenna height on all but the highest frequency band was necessarily less than one quarter wavelength resulting in a radiation resistance which progressively decreased from a high impedance on the highest frequency of operation to a few ohms on the lowest frequency of operation. Second, the use of numerous traps and other loading devices increased the system Q and unnecessarily restricted the bandwidth, especially on the mid-range HF (high frequency) frequencies where the active radiator height could be less than that required for unloaded resonance operation. Third, from a mechanical viewpoint, the use of numerous traps and loading devices in the upper sections of the vertical antenna made for a relatively unstable and heavy structure which required heavy and expensive construction for a freestanding wind survival rate. Fourth, a further difficulty had to do with the ease of adjustments for resonance at the desired frequencies in the low HF frequencies. Inasmuch as adjustment in the past for these frequencies had to be made in the upper sections of the antenna, the entire vertical antenna had to be removed from its mounting and brought to ground level for the slightest readjustment. This was a particularly inconvenient feature of operation as the effective operating bandwidth of the vertical antenna was generally less than twenty percent of the authorized band spectrum. Finally, the prior art vertical antennas could not easily or conveniently be extended to provide additional resonance on the one hundred and sixty meter band, as the additional height required greatly complicated the physical construction of the vertical antenna. Therefore, the prior art commercially available multi-band vertical antennas have not provided a simultaneous one hundred and sixty meter capability.

The present invention provides a vertical antenna that overcomes all the disadvantages of the prior art vertical antennas.

The general purpose of this invention is to provide a high frequency vertical antenna which is resonant on six amateur radio HF bands.

According to one embodiment of the present invention, there is provided a high frequency vertical antenna for use on the amateur radio high frequency spectrum segments having an eighty meter capacitor section and including an adjustable resonator connected across the capacitor section, a forty meter capacitor section connected to the eighty meter capacitor section and including an adjustable resonator connected across the capacitor section, a fifteen meter trap section connected to the forty meter capacitor section and an upper vertical radiating section connected to the fifteen meter trap section whereby the overall antenna height is resonated on eighty and forty meters, the vertical antenna resonates as a quarter wavelength on twenty meters, the vertical antenna resonates as a quarter wavelength on fifteen meters because of decoupling of the upper vertical radiating section of the antenna by the fifteen meter trap section, and the vertical antenna resonates as a three-quarters wavelength on ten meters.

A one hundred and sixty meter tuner can be added to the base of the vertical antenna for simultaneous resonance on all six HF amateur bands of one hundred and sixty meters through ten meters of the high frequency spectrum.

One significant aspect and feature of the present invention is a vertical antenna which is omnidirectional including completely automatic band switching, and can operate on all HF amateur frequencies of one hundred and sixty meters through ten meters.

Having briefly described one embodiment of the present invention, it is a principal object hereof to provide a vertical antenna for operation on the high frequency amateur radio frequencies of one hundred and sixty meters through ten meters. The frequency segments are one hundred sixty meters, eighty-seventyfive meters, forty meters, twenty meters, fifteen meters, and ten meters. While the present invention has been disclosed for use on the six amateur radio frequency segments of the high frequency spectrum, the specification is not to be construed as limiting as the principles of operation can be extended to any frequencies of operation as predetermined.

An object of the present invention is a vertical antenna which operates on all of the amateur radio HF spectrum assignments as set forth by the Federal Communications Commission and requires no manual band switching when changing frequencies. The band switching is automatic and electrical in the literal and figurative sense in that the entire height of the vertical antenna radiates on all frequencies except for fifteen meters where the upper portion of the antenna is automatic and electrically trapped out for quarter wavelength operation on fifteen meters. The automatic and electrical band switching eliminates the need for manual band switching from the physical antenna itself or from a remote point.

Another object of the present invention is to provide a vertical antenna with fewer traps or tuned circuits than the prior art vertical antennas thus simplifying the vertical antenna with resultant economies in time and construction materials. By utilizing resonator capacitor sections, fewer traps are required.

A further object of the present invention is to provide a vertical antenna having greater efficiencies because of the active radiating sections on the upper high frequency spectrum segments. Consequently, the bandwidth is increased on the upper high frequency spectrum segments because of the lower Q of the longer radiating sections for each of the spectrum segments, particularly the forty meters through ten meter bands.

An additional object of the present invention is to provide a vertical antenna which provides readily accessible in-place adjustment on the forty and eighty meter bands where the Q is the highest and where the bandwidth is typically much less than the entire band by moving a coil clamp along the vertical length of the eighty meter and forty meter resonator capacitor sections.

A still additional object of the present invention is to provide a vertical antenna which has small wind loading because the frequency control circuits are mounted in and on the lower half of the vertical antenna. The upper half of the antenna only needs to support its own weight thereby being much lighter and requiring smaller diameter metal tubing.

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood, by reference to the following detailed description when considered in connection with the accompanying drawings, in which like reference numerals designate like parts throughout the figures thereof and wherein:

FIG. 1 illustrates a plan view of a vertical antenna, the present invention;

FIG. 1A illustrates a section of the present invention taken on the line 1A--1A of FIG. 1 looking in the direction of the arrows;

FIG. 1B illustrates a section of the present invention taken on the line 1B--1B of FIG. 1 looking in the direction of the arrows;

FIG. 1C illustrates a section of the present invention taken on the line 1C--1C of FIG. 1 looking in the direction of the arrows;

FIG. 2 illustrates a plan view of a one hundred and sixty meter tuning unit mounted at the base of the vertical antenna.

FIG. 1, which illustrates a vertical plan view of a vertical antenna 10, the present invention, shows a metal hollow tubular mounting post 12 having a solid tubular fiberglass insulator 14 of a diameter to telescope internally into the mounting post 12, and secured thereto with a nut and bolt assembly 16. An eighty-seventyfive meter resonator capacitor metal section 18 having a lower hollow tubular portion of a diameter telescopes over the solid insulator 14, and is secured thereto with a nut and bolt assembly 20. An eighty meter resonator coil 22 clamps between a top portion of the eighty meter resonator capacitor section 18 to a position immediately below an insulator assembly 24 as later described in FIG. 1A. Coil clamps 22a and 22b surround the top portion of the eighty meter resonator capacitor section 18, position immediately below the insulator assembly 24 respectively, and are secured thereto with nut and bolt assemblies in addition to securing the respective ends of the coil 22 as later described in FIG. 1A. A self-tapping screw 22c secures the top coil clamp 22a to the top portion of the eighty meter resonator capacitor section 18. A forty meter resonator capacitor metal section 26 having a lower hollow tubular lower portion of a diameter to telescope over the eighty meter resonator capacitor section above the insulator assembly 24, and secures thereto with a self-tapping screw 28. A forty meter resonator coil 30 clamps between a top portion of the forty meter resonator capacitor section 26 to a position immediately below an insulator assembly 32 as later described. Coil clamps 30a and 30b surround the top portion of the forty meter resonator capacitor section and position immediately below the insulation assembly 32 respectively, and are secured thereto with nut and bolt assemblies in addition to securing the respective ends of the coil 30. A self-tapping screw 30c secures the top coil clamp 30a to the top portion of the forty meter resonator capacitor section 26. A lower end of a first metal section of hollow tubing 34 is of a diameter to telescope over the top portion of the forty meter resonator capacitor section 26 above the insulator assembly 32, and secures thereto with a self-tapping screw 35. A fifteen meter trap section 36 having a lower hollow tubular portion and including a lower slotted end 38 is of a diameter to telescope over the top of the hollow tubing 34, and is secured thereto with a hose clamp 39.

A fifteen meter trap 40 having a coil 42 wound on a coil form 42a between two self-tapping screws 42b and 42c secures over an upper portion of the fifteen meter trap section 36 with a self-tapping screw 42d as later described. A second hollow metal section of tubing 44 having an upper slotted end 46 is of a diameter to telescope into the top of the fifteen meter trap section 36, and secures thereto with a self-tapping screw 48. A third hollow metal section of tubing 50 is of a diameter to telescope into the second hollow tubing 44, and secures within the slotted end 46 within a hose clamp 52. A fourth hollow metal section of tubing 54 is of a diameter to telescope into said third hollow section of tubing 50, and secures therein with a self-tapping screw 56. A fifth hollow metal section of tubing 58 is of a diameter to telescope into the fourth section of tubing 54, and secures therein with a self-tapping screw 60. An impedance matching coil 62 connects between the nut and bolt assembly 20 in the bottom of the eighty meter resonator capacitor section 18, and the nut and bolt assembly 16 in the top of the hollow tubular mounting post 12. A matching section length of seventy-five ohm coaxial cable transmission line 64 connects in parallel across the impedance matching coil, and terminates in a suitable coaxial plug such as a PL-259. An electrical ground connects to the nut and bolt assembly 16, and the metal hollow tubular mounting post 12. The metal portions of the vertical antenna 10 can be aluminum tubing of predetermined diameter by way of example and for purposes of illustration while the insulators can be fiberglass, polyethylene, etc. by way of example and for purposes of illustration as later described.

FIG. 1A, which illustrates a section of the vertical antenna taken on the line 1A--1A of FIG. 1 looking in the directions of the arrows, shows an internal metal tube 68 spaced by spacers 70a and 70b as illustrated in the figure from the eighty meter resonator capacitor metal section 18. An insulation sleeve 72, such as fiberglass by way of example and for purposes of illustration only, is accommodated between the eighty meter resonator capacitor section 18 and the internal tube 68. A first metal shim tube 74 of a predetermined diameter telescopes over the internal tube 68 and into the fiberglass sleeve 72. A second metal shim tube 76 of a predetermined diameter telescopes over the first metal shim tube 74 and abuts up against the top of the fiberglass sleeve 72. A third metal shim tube 78 of a predetermined diameter telescopes over the second metal shim tube 76 and abuts up against the top of the fiberglass sleeve 72. An insulation sleeve 80 such as polyethylene by way of example and for purposes of illustration only, extends and surrounds the fiberglass sleeve 72, and extends to a point just above the fiberglass sleeve 72 and to a point just below the top of the eighty meter resonator capacitor metal section 18. The top coil clamp 22a clamps around the third metal shim tube 78 and is electrically affixed thereto with the self-tapping sheet metal screw 22c which passes through the metal tubes 78, 76, 74 and 68 in order. The bottom metal coil clamp 22b being identical to the top coil clamp 22a clamps around the eighty meter resonator capacitor metal section 18 as later described in detail. The coil 22 of sixteen turns of aluminum tie wire by way of example and for purposes of illustration only on a four inch diameter connects between the top coil clamp and the bottom coil clamp 22a and 22b respectively. The coil clamp 22b includes overlapping flanges 22b.1 and 22b.2 illustrated in imaginary line having bolt holes 22b.3 and 22b.4 illustrated as overlapping to accept a nut and bolt assembly for clamping action. Additionally, an extending flange 22b.5 extends perpendicular to the overlapping flange 22b.1, and is provided with a hole to accept bolt 22b.6, the end of the coil wire 22b.7, a flat washer 22 b.8, a lock washer 22b.9, and a nut 22b.10.

FIG. 1B, which illustrates a section of the vertical antenna taken on the line 1B--1B of FIG. 1 looking in the direction of the arrows, shows an internal metal tube 82 spaced by spacers 84a and 84b from the forty meter resonator capacitor metal section 26. An insulation sleeve 86 such as fiberglass by way of example and for purposes of illustration only is accommodated between the internal tube 82 and the forty meter resonator capacitor metal section 26. A first metal shim tube 88 telescopes over the internal metal tube 82 and abuts up against the top of the fiberglass sleeve 86. An insulation sleeve 90 such as polyethylene by way of example and for purposes of illustration only, extends and surrounds the fiberglass sleeve 86, and extends to a point just above the fiberglass sleeve 86 and to a point just below the top of the forty meter resonator capacitor metal section 26. The top coil clamp 30a clamps around the first metal shim tube 88 and is electrically secured thereto with the self-tapping screw 30c which passes through the metal tubes 82 and 88 in order. The bottom metal coil clamp 30b clamps around the forty meter resonator capacitor metal section 26. The coil 30 of eleven turns of aluminum tie wire by way of example and for purposes of illustration only, on a four inch diameter connects between the top and bottom coil clamps 30a and 30b respectively.

FIG. 1C, which illustrates a section of the vertical antenna taken on the line 1C--1C of FIG. 1 looking in the directions of the arrows, shows an internal metal tube 92 spaced by spacers 94a and 94b from the fifteen meter trap metal section 36. An insulation sleeve 96 such as fiberglass is accommodated between the fifteen meter trap section 36 and the internal tube 92. A first metal shim tube 98 telescopes over the internal tube 92 and abuts up against the top of the insulation sleeve 96. The fifteen meter trap 40 includes the coil 42 wound on the coil form 42a of suitable insulation which telescopes over the fifteen meter trap section 36, and secures thereto with self-tapping screws 42b and 42d through the metal shim tube 98 and the internal tube 92. Self-tapping screw 42c secures to metal section tube 36 through a metal shim ring 37 which telescopes over the tube section 36. An end cap 100 accommodates additional space between the coil form 42a and the metal shim tube 98. An insulation spacer 102 accommodates additional space between the coil form 42a and the metal section tube 36. The coil 42 consists of three turns of number twelve copper wire wound on the two inch diameter form 42a, and connects to the top and bottom screw 42b and 42c respectively.

FIG. 2 which illustrates another embodiment of the vertical antenna shows a vertical plan view of a one hundred and sixty meter capacitor metal section 104 shows the internal metal tube 106 spaced from the one hundred and sixty meter capacitor section 104 by an insulation tube 108 such as polyethylene. An end cap 110 such as plastic covers the top of the tubes 104, 106 and 108 respectively. Two short metal shim rings 112a and 112b support a plastic coil form 114 which telescopes and slides over the one hundred and sixty meter capacitor section tube 104. An upper coil clamp 116 clamps around the top portion of the plastic coil form 114, and a middle coil clamp 118 clamps around the lower portion of the plastic coil form 114. A wire coil 120 of twenty-two turns of number fourteen close wound on the two inch diameter coil form connects between the upper coil clamp and the middle coil clamp as previously described. The coil 120 can be coated with ABS cement to retain proper coil spacing on the coil form 114. A self-tapping sheet metal screw extends through the upper coil clamp 116, the plastic coil form 114, the short metal tube or ring 112a, and the point of the self-tapping screw frictionally protrudes into the one hundred and sixty meter capacitor section tube 104. A lower coil clamp 124 clamps around the extending portion of the internal tube 106 below the polyethylene sleeve 108. A coil 126 of tie wire of ten turns on a four inch diameter connects between the middle and lower coil clamps 118 and 124 respectively. A bracket 126 with two pairs of U-bolt assemblies 126a-126d respectively fastens the one hundred and sixty meter capacitor section 104 to the eighty meter resonator capacitor section 18.

The mounting post 12 of FIG. 1 is set into a suitable hole, approximately in the range of twenty-one inches deep, so that the upper end of the insulator 14 clears the ground by five or six inches. The earth is packed tightly around the mounting post and concrete can be utilized for additional strength.

A number eight one and three-quarter inch bolt 16 is passed through the braid lug of the coaxial cable impedance matching transmission line 64, through a flat washer, through the lower loop of the impedance matching coil 62, through another opposing flat washer, through the hole in the mounting post 12 and the insulator 14, and secured with a flat washer, a lock washer, and a number eight nut. The eighty meter resonator coil 22 has two clamps, one large 22b and one small 22a. Remove a bolt assembly from the large clamp 22b and spread the large clamp 22b slightly. The top of eighty meter resonator capacitor section 18 is first passed through the large clamp 22b, the eighty meter resonator coil 22, and then through the small clamp 22a. The larger clamp 22b is below the insulation 24. The screw hole in the small clamp 22a of eighty meter resonator coil 22 is aligned with the lower screw hole in the top of section 18, and secured with a number ten-twentyfour self-tapping screw 22c through the small clamp 22a into the eighty meter resonator capacitor section 18. The one-quarter inch by one inch bolt is replaced in the large clamp 22b, the large clamp 22b is slid down the eighty meter resonator capacitor section 18 to a predetermined position, and subsequently, the large clamp 22b is tightened. The forty meter resonator coil 30 is installed on the forty meter resonator capacitor section 26 in a like manner and tightened at a predetermined position.

The lower end of first metal section 34 telescopes onto the top of forty meter resonator capacitor section 26. The screw holes are aligned in the sections 34 and 26, and secured with a number ten-twentyfour self-tapping screw 35. The large stainless steel hose clamp 39 is positioned over the slotted end 38 of the fifteen meter trap section 36, and the two sections 36 and 34 telescope together. The distance between the trap coil 40 of the fifteen meter trap section 36 and the top of forty meter resonator coil 30 is adjusted to the range of five feet-eight inches, and the clamp 39 is tightened. The bottom of second metal section 44 telescopes into the top of fifteen meter trap section 36, and the screw holes are aligned and secured with a number ten-twentyfour self-tapping screw 48. The fourth metal section 54 telescopes into the third metal section 50, and the screw holes are aligned and secured with a number ten-twentyfour self-tapping screw 56. The fifth metal section 58 telescopes into the fourth metal section 54, and the screw holes are aligned and secured with a number six-thirtytwo self-tapping screw 60. The small stainless steel hose clamp 52 is positioned over the top slot end 46 of the second metal section 44. The bottom of the third metal section 50 telescopes into the top of the second metal section 44, the distance from the top of the trap decoupling coil 40 to the top of the fifth metal section 58 is adjusted to the range of thirteen feet-two inches, and the hose clamp 52 is tightened. The bottom of the eighty meter resonator capacitor section 18 is positioned over the top of the mounting post 12, and the screw holes aligned. A number eight by one and three-quarters inch bolt 20 is passed through the center lug of the coaxial cable impedance matching transmission line 64, through a flat washer, through the upper loop of the impedance matching coil 62, through another opposing flat washer, through the sections 18 and 14 and is secured with a flat washer, a lock washer, and a number eight nut. The assembly of sections 26-58 is raised and positioned atop by telescoping the bottom of the forty meter resonator capacitor section 26 over the top of the eighty meter resonator capacitor section 18, aligning the screw holes, and securing with a number ten-twentyfour self-tapping screw 28.

The vertical antenna 10 produces a very low standing wave ratio (SWR) readings over the twenty, fifteen, and ten meter bands, and the eighty-seventyfive and forty meter resonator circuits are predetermined and set for resonances of approximately 3700 and 7100 Khz. Inasmuch as some variation can be expected, the following procedure is utilized to adjust the vertical antenna 10 for minimum SWR at any desired point in each of the five bands of the HF spectrum. SWR readings can be taken at the transmitter end of the coaxial cable transmission feedline, or at the junction of the coaxial cable transmission feedline which is fifty-two ohm and the seventy-five ohm impedance matching transmission line 64 for greater accuracy.

The frequency of minimum SWR on fifteen meters is predetermined. To raise the frequency, the sliding sections 34 and 36 are telescoped closer together or to lower frequency, the sections 34 and 36 are slid further apart. The frequency of minimum SWR on twenty meters is predetermined. To raise or lower the frequency, the total length of sections 44 through 58 is adjusted by varying the amount of overlap between sections 44 and 50 a few inches. The frequency of minimum SWR on ten meters is predetermined. The twenty meter adjustment also determines the ten meter resonant frequency, but resonance on both bands is so broad that slight adjustments for the sake of improved SWR on one band does not significantly affect SWR on the other. The frequency of minimum SWR on forty meters is predetermined. Adjustment is made by loosening the lower clamp 30b of the forty meter resonator coil 30, and compressing or expanding the spacing between coil turns to lower or raise the frequency respectively. One half-inch of travel will move the frequency of minimum SWR by approximately seventy Khz. When the proper setting has been determined, the lower clamp 30b is tightened in place. The frequency of minimum SWR on eighty or seventy-five meters is predetermined. Adjustment is made in a like manner by repositioning the lower clamp 22b on the eighty-seventyfive meter resonator coil 22. When the proper setting has been determined and the lower clamp 22b is tightened, the impedance matching coil 62 is adjusted at the base of the vertical antenna 10 by spreading the turns farther apart or squeezing them closer together until the SWR drops to a minimum value. One adjustment of the impedance matching coil should suffice for operation over the entire 3500-4000 Khz range, provided that the necessary adjustments are made to the eighty-seventyfive meter resonator coil 22. In general, the forty and eighty-seventyfive meter adjustments will not significantly affect adjustments previously made for twenty, fifteen, and ten meters. However, if the eighty-seventyfive meter tuning is readjusted for operation at a much higher or lower frequency, it may be necessary to readjust the forty meter tuning in order to maintain SWR of less than 2:1 at both band edges.

The one hundred sixty meter tuning unit 104 of FIG. 2 utilizes a combination of fixed and variable inductance in a high-capacitance parallel-tuned circuit to generate the inductive reactance required to resonate the vertical antenna 10 in the 1800-1850 Khz range. At higher frequencies of the HF spectrum, the one hundred and sixty meter tuning unit 104 produces decreasing values of capacitance reactance which virtually have no effect on twenty, fifteen and ten meter operation, and which exert only a slight detuning effect on eighty and forty meter operation. The hundred and sixty meter tuning unit 104 provides for simultaneous resonance in each of the six HF amateur bands of the HF spectrum.

The one hundred and sixty meter unit is installed as illustrated in the FIG. 2. The resonance frequency is adjusted by loosening the set screw 122 approximately one third turn counterclockwise and sliding coil assembly 114 upwards along the tubular capacitor thus pulling the turns of the air wound inductor slightly apart. The resonant frequency is lowered in an opposite like manner. Set screw 122 is retightened at the proper setting. On obtaining a setting for one hundred and sixty meter operation, it may be necessary to readjust the eighty and forty meter resonator circuits as previously described.

The vertical antenna 10 is constructed of commercially available components including aluminum tubing of 5/8, 3/4, 7/8, 1 and 11/8 inch outer diameters of predetermined lengths, aluminum tie wire, polyethylene tubing, ABS cement, fiberglass sleeves and insulators, and the like components. The aluminum tubing can be 0.058 wall 6061--T6 leading to an antenna weight in the range of ten and one-half pounds. The height of the antenna is 26 feet. The eighty meter resonator capacitor section 18 is five and one-half feet; the forty meter resonator capacitor section is twenty inches; the first section 34 is one inch by thirty-three inches; the second section is three-quarters by four feet, top slotted; the third section is five-eighths by four feet with a screw hole in the top; the fourth section is one-half by four feet, with a large screw hole in the bottom and a small screw hole in the top, and; the fifth section is three-eighths by three feet with a screw hole in the bottom and the top closed.

The vertical antenna is capable of handling transmitter input power of 2000 watts SSB or 1000 watts CW on forty-ten meters, 1500 watts PEP or 500 watts CW on eighty-seventyfive meters. Fifty ohm coaxial cable transmission line connects to the impedance matching section 64. The VSWR at resonance is 1:5:1 or less with a VSWR 2:1 or less for forty through ten meters and 60-100 Khz on eighty meters.

Various modifications can be made to the vertical antenna of the present invention without departing from the apparent scope thereof.