All About the Discone : Antenna of Mysterious Origin and Superb Broadband Performance Learn about the development, history and some applications of a .

Steve Stearns, K6OIK

he frequency bandwidths as extensions of it.1 The discone antenna ent on the discone antenna. Kandoian’s novel “ demanded by high-definition (Figure 1) is one such extension, in which the or inventive element was apparently that the T television have considerable biconical dipole is asymmetric, one cone’s antenna could be encased in a radome, making range…” With these prescient words, Philip angle being 90°, which gives a flat disk of ra- it suitable for aircraft, not that it used a cone or S. Carter of RCA opened a 1939 paper that dius equal to the cone length. Two years later, disk per se, those ideas being obvious in view compared a variety of antennas for the emerg- in 1943, Armig Kandoian at the Federal Tele- of Schelkunoff’s prior work. The patent was ing field of “high-definition” television. Carter phone and Corporation applied for a pat- granted in 1945, whereupon Kandoian and his showed conclusively that conical antennas colleagues, Sichak, Felsenheld, and Nail, at held distinct advantages over dipoles and fold- 1Notes appear on page 43. the newly renamed Federal Telecommunica- ed dipoles when it comes to broadband perfor- mance. Today, conical antennas are making a comeback for broadband applications such as digital television and UWB (ultra-wideband) or impulse radio. Stacked arrays of bowties and biconical dipoles are gradually displacing traditional mainstay antennas such as Yagis and log-periodics for the rooftop reception of digital television (DTV). One conical antenna, long popular among scanner hobbyists, the discone, has been described in previous ar- ticles in magazines and books. The story has never been told fully, however. This article explains the history and theory of the discone, corrects some common misunder- Figure 1 — This standings, and presents an EZNEC model for a illustration shows a 0.6-octave discone that readers may copy and home-made discone for 2.4-GHz WiFi use. See scale to their favorite frequency bands. www.spaziolink.com/wi-fi. Conical antennas, and the discone in par- ticular, have an obscure but fascinating history. Sergei Alexander Schelkunoff, at Bell Labs, was a titan of antenna theory in the early to mid 20th Century. In 1941, Schelkunoff pub- lished a major paper in the Proceedings of the IRE, which, among other things, analyzed the symmetric biconical dipole and showed that many other antennas can be analyzed

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Jan/Feb 2007 37 tion Laboratories, a subsidiary of ITT, began side of the cone), and the radius of the ground for a cone depending on design impedance publicizing the antenna in a series of articles plane disk. SWR depends addition- and bandwidth. More exact formulas for when in various journals from 1946 to 1953. ally on the line’s characteristic impedance. A the disk radius is finite are in the engineering In 1952, Schelkunoff published the book discone is not a frequency independent an- literature. We’ll use an EZNEC model when Advanced Antenna Theory, which gave a tenna, although this is a common misconcep- analyzing such cases. comprehensive analysis of the asymmetric tion. Rather, a discone behaves more like a fat In his 1941 paper, Schelkunoff showed biconical dipole in which the angles and dipole. Its feed point resistance and reactance that the feed point impedance of many lengths of both cones are arbitrary. The dis- vary with frequency, although not through the antennas, including the conical monopole cone appeared on page 93 as a special case. extremes of a dipole. over a , can be represented as Engineering studies of the discone followed Discones are used for broadband op- terminated transmission lines one-quarter shortly thereafter by Nail at the Federal Tele- eration at frequencies above their first reso- wave shorter than the length of the antenna: communication Laboratories and by Crowley nance. Manufacturer’s data for two popular π  and Marsh at Ohio State University. Many VHF/UHF discones, the AOR DA3000 and Zm + jZ0 tan  k −  variations on the basic discone have appeared RadioShack 20-043 are shown in Figures 2  ZZin = 0 since, having such features as multiple cones, 2 and 3 as graphs of return loss versus fre- π  multiple disks, meander lines for the cone, quency. The vertical scale of the AOR curve Z0 + jZm tan  k −  and mechanical tuning devices. is 10 dB/division; the scale of the RadioShack 2  (Eq 1) Radio Amateurs, meanwhile, had noticed curve is unspecified. The key feature is that For a conical monopole of angle θ, mea- this interesting antenna. A construction article the curves are scalloped. The SWR cycles sured from axis, the characteristic impedance appeared in CQ in 1949. More construction between high and low as frequency is varied. Z0 is given by: articles appeared since then, and are noted at Receiving is possible on any frequency, but the end of this article. Given such interest, it transmitting is best done in the SWR valleys. η θ  is surprising that amateur antenna modelers A good design will keep the SWR peaks be- Z0 = ln cot   have largely overlooked this antenna. This low a design limit and position the valleys to 2π  2  (Eq 2) article corrects that oversight by presenting an coincide with desired transmit frequencies. The terminating impedance Zm = Rm + jXm EZNEC model for a discone that readers may There are, broadly speaking, two methods is the radiation impedance referenced to the copy, modify, or scale to their favorite bands. for analyzing antennas that don’t require con- current maximum on the antenna. Schelku- Conical antennas consisting of a single struction and measurement. The first method noff gave general formulas for the real and cone fed at its apex against an infinite ground is mathematical analysis, and the second is imaginary parts of Zm for all cone angles, plane are often called “monocones” or less numerical antenna modeling. The former was but he also gave the formulas for small cone often “unipoles.” If the infinite ground plane is the only method available before comput- angles in Equation 3 below, where k is the replaced by one that is finite and circular, the ers were invented. Antennas were analyzed wavenumber 2π/λ and η is the characteristic antenna is called a “discone.” A discone can mathematically by “normal mode theory” or impedance of free space equal to µoc, the also be thought of as an asymmetric biconical by solving integral equations. In this article, speed of light times the magnetic perme- dipole in which one cone’s angle is 90° (mea- we’ll use a formula developed by Schelkunoff ability of free space, or 376.73 Ω. (It would sured from its axis), so it opens to become a flat for the feed point impedance of a finite cone be exactly 120π Ω if light would cooperate disk. The impedance of a discone depends on over an infinite ground plane, derived from and travel at exactly 300 million meters per frequency and three geometric variables: the spherical mode theory. The formula allows us second.) Other symbols in the formulas are cone’s angle, slant length (measured along the to quickly determine the best length and angle Euler’s constant, C = 0.5772156649… and

η  1 1  R= C +ln2 k − Ci2 k  + sin2k Si4 k − 2Si2 k   + cos2k C+ ln k  + Ci4 k  − 2Ci2 k   m  ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) 4π  2 2  (Eq 3) η  1 1  X = Si 2k − sin 2k C+ ln k  − Ci 4 k   − cos 2k Si 4 k  m  ( ) ( ) ( ) ( ) ( ) ( ) 4π  2 2 

Figure 3 — Return loss of RadioShack 20-043 discone antenna.

Figure 2 — Return loss of AOR DA3000 discone antenna.

38 Jan/Feb 2007 Figure 4 — Computed SWR (at 50 and 75 Ω) of two 100-foot Figure 5 — Nominal monocone and discone impedance versus cones. cone angle.

the sine and cosine-integral functions Si(x) and Ci(x), which we won’t explain here. Schelkunoff’s asymptotic formula isn’t numerically accurate for discones having large cone angles or finite disk radii. The formula, however, does reveal general trends and interesting design trades. More accurate formulas for general discones and biconical dipoles or “bicones” were developed by Hahn and Fikioris, and most recently by Samaddar and Mokole.2 For broadband operation, the best cone angle depends on band-

width. Given a frequency band from f1 to f2, the optimum cone angle decreases as the ratio f2/f1 increases. For a nominal 50-Ω antenna, as the design bandwidth increases from one to five octaves, the optimum cone angle decreases from 47° to 39°, and the peak SWR creeps up. In addition, as the feed point design impedance increases, the optimum cone angle decreases. An interesting implication pursued in some designs is that the cone should be curved instead of flat sided. Our Figure 6 — Predicted SWR of three antennas optimized for UHF interest here is flat-sided cones. TV.

Figure 7 — Wire table of an EZNEC discone model.

Jan/Feb 2007 39 Figure 4 shows SWR curves calculated length is adjusted to put the SWR valleys on to 329 MHz or a wavelength of 91 cm. The from Schelkunoff’s formula for two 100-foot the desired transmit frequencies. Alternatively, disk radius plus cone slant length should cones over infinite ground planes. The cone an SWR valley can be shifted to a transmit fre- equal half of this number or 46 cm. Now, you angle and length have been optimized for five- quency by using a mechanical tuning scheme could allocate this length equally to the disk octave operation at both 50 and 75 Ω. Now, we such as those of McNamara or Rappaport. radius and cone slant length, making them can use an antenna modeling program to get When constructing a discone, the cone both 23 cm. This may not be the best way better accuracy with less effort. Nonetheless, I and ground plane can be made from rods or to divide the length, however. Nail suggests found the best cone angles for each feed point sheet metal as illustrated in Figure 1. When that for a 50-Ω design, the ratio of radius to impedance in a five-octave band with a single using rods, at least eight should be used. The cone length should be: command to Microsoft Excel’s solver tool AOR DA3000 uses 16, while the Diamond and 60 seconds of patience. Doing the same D-130J and RadioShack 20-043 use eight. R =0.72 × sinθ optimization in EZNEC would have taken You can adjust the impedance by bending L days if EZNEC had an optimizer — which it the rods in or out. This is an advantage of (Eq 5) doesn’t, unfortunately. rod construction. which gives R/L = 0.36 or the ratio R:L = 26:74 An approximate formula for the best cone for a cone angle of θ = 30°. An antenna model- Example angle for a given feed point design impedance ing program can be used to confirm this ratio is obtained from the characteristic impedance As an example, we’ll consider a discone or to find a better ratio for a different design formula above. for receiving UHF TV channels 14 through impedance. You can vary the proportions: 53. The frequency range is 470 MHz to −Z 10:90, 20:80, 30:70, 40:60, 50:50 and so on, −1 0  710 MHz. We set the discone’s first resonance θ = 2tan exp  and compute an SWR sweep for each com- 60  at a frequency below 470 MHz because, as bination to find what ratio gives the smallest (Eq 4) shown in Figure 4, the SWR shoots up below peak SWR over the band of interest. Figure 5 illustrates the relation between θ the first resonance. Making the antenna too Let’s consider the UHF TV antenna and Z0 given by this approximation. The pre- small incurs a big penalty. example. To keep things simple, we’ll let dicted angle is good for design bandwidths A rule of thumb is to set the first resonant the disk be an infinite ground plane and up to two octaves but should be reduced if frequency at 0.7 times the lowest operating use Schelkunoff’s asymptotic formula; in the design bandwidth is greater. frequency. In this example, that comes out practice, we’d use EZNEC and include disk There are a lot of different ideas about the proper shape of a discone. Typing “discone” into Google Images reveals a variety of shapes. A common error appears to be mak- ing the disk too small and the cone too long. Using a computer, one can jointly optimize a cone’s angle, slant length, and disk radius. In- creasing the disk radius while simultaneously decreasing the cone’s slant length is akin to Figure 8 — sliding a feed point along an off-center-fed Geometry of EZNEC (OCF) dipole. This interpretation becomes discone model. exact if we regard the discone as an OCF biconical dipole with one cone’s angle being 90°. Computer modeling reveals the best geometry for a given design impedance and band of operation, as will be shown below. The procedure for designing a discone for transmitting has one extra step. The slant

Figure 9 — SWR sweeps at (A) 50 Ω, and (B) 75 Ω; the marker is at 460 MHz.

40 Jan/Feb 2007 radius as a variable. The goal is to find the using EZNEC’s radial tool to complete the explicitly optimized for 50 Ω, the dimensions cone angle and slant length that together model. Wire 1 is the prototype wire for the are fairly good for that impedance too. This is minimize the maximum SWR between 470 disk. Wires 2 through 16 were created by not mere coincidence but a consequence using MHz and 710 MHz. We’ll find design dimen- EZNEC. Similarly, Wire 17 is the prototype Nail’s recommended disk size, which is for a sions for 50 and 75 Ω discones and a 300 Ω wire for the cone, and Wires 18 through 32 50-Ω design, rather than a 75-Ω design. biconical dipole. A biconical dipole has a were created by EZNEC. It’s convenient to EZNEC’s 500-segment restriction limits balanced feed point. When designing televi- think of cone and disk wires as being grouped the bandwidth for which it can be used. sion antennas having balanced feed points, into 16 pairs, with 31 segments allocated to A minimal NEC model would have eight it is customary to make the feed point 300 Ω each pair. Segment lengths are made nearly wires for the cone and eight wires for the because this permits using both 300-Ω bal- equal by allocating 25% of the segments to disk. If the length of each wire is a quarter anced twin lead and 75-Ω coaxial line with the disk and 75% to the cone. Disk wires, wavelength or λ1/4 at the lowest frequency a 4:1 current balun. therefore, have 8 segments, and cone wires f , then the total length of all 16 wires is 8 λ . Numerical optimization quickly finds the 1 1 have 23 segments. This gives segment lengths The segment length should be no greater than best lengths and cone angles. The optimum of 11 mm for the disk and 11.7 mm for the λ /20 where f is the highest frequency. The lengths are 29, 27, and 24 cm, with cone 2 2 cone wires. The apex of the cone was offset number of segments, obtained by dividing angles of 32°, 27°, and 19° respectively for by 11 mm from the plane of the disk to make the segment length into the total length, is 50 and 75-Ω discones and a 300-Ω bicone. room for a single-segment source wire, which 80 λ /λ . Because EZNEC can handle at most Notice that the lengths are greater than those 1 2 is Wire 33. The total number of segments 500 segments, the frequency ratio cannot ex- given by the rule of thumb. The reason is in the model is 497, and the segment size is ceed f /f = 500/80 = 6.25, or 2.6 octaves. So, that the design bandwidth is narrow enough 2 1 under λ/25 up to 1 GHz, which is well above very broadband design should be done with a that lengthening the antenna moves an SWR the upper band limit of 710 MHz. modeling program that can handle more than valley down to fit the band. A more revealing Figure 9 shows the SWR predicted by 500 segments, at least 80 f /f segments. explanation will be given shortly on a Smith 2 1 EZNEC for 50 and 75-Ω reference imped- It’s always a good idea to check whether Chart. Figure 6 shows the predicted results. ances. The graphs’ vertical scales are nonlin- a simple impedance matching network can For a 75-Ω design impedance, the best ear in SWR but linear in reflection coefficient improve the match over the band. The first step combination of cone angle and length were magnitude. Allowing for graph distortion when designing a matching network is to plot found to be 27° and 27 cm. The predicted created by the nonlinear scale, the 75-Ω SWR the antenna impedance data on a Smith Chart. SWR is the darker curve in Figure 6. The curve on the right can be compared to that for We’ll use the impedance data that EZNEC maximum SWR between 470 and 710 MHz the 75-Ω conical monopole shown in Figure computed. EZNEC’s frequency sweep fea- is predicted to be 1.82. 6 (darker curve) which was computed from ture allows the option of creating output data At this point we are ready to consider the Schelkunoff’s asymptotic formula. The two files for MicroSmith or winSMITH. It’s best effect of a finite disk radius. We’ll check the curves are highly similar in both shape and to choose MicroSmith to avoid winSMITH’s theoretical predictions by using an EZNEC value. It’s clear that the dimensions obtained limit to 15 frequencies. EZNEC puts complex antenna model that includes a finite disk by optimizing Schelkunoff’s formula are reflection coefficient (scattering parameter having Nail’s recommended radius. quite good, but there’s still room for improve- S11) data in a .GAM text file. It should be R = L × 0.72 × sin θ (Eq 6) ment. At this point one might choose to either opened with Microsoft Word, where it can be R = 27 × 0.72 × sin 27° = 27 × 0.72 × 0.4540 build and test the antenna with the current manipulated into a standard format for what- = 8.8 cm dimensions or refine the EZNEC model. ever EDA program you use, such as ARRL It is noted that the model performs well Radio Designer, Ansoft Serenade SV (featured The discone model’s wire table and geom- as a 50-Ω antenna as shown in the left curve in January 2001 QST), Agilent ADS, AWR etry are shown in Figures 7 and 8. The model of Figure 9A. The computed SWR is 1.54 Microwave Office, RFSim99, or even good old was created easily by defining two wires as and 1.58 at the band edges and achieves a SPICE. I have found that Ansoft Serenade SV prototypes for the disk and cone, and then minimum of 1.30 at 610 MHz. Although not has the best capabilities for the money.

Figure 11 —SWR of unmatched discone (referenced to 75 Ω). Figure 10 — Discone impedance on 75 Ω Smith Chart; UHF TV band highlighted with a darker band.

Jan/Feb 2007 41 Figure 12 — An open stub impedance-matching network for 75 Ω.

Figure 13 — The match performance of an open stub is shown on a 75 Ω Smith Chart.

Figure 9B confirms that the EZNEC data con- version was done correctly. The data is plot- Figure 14 — The matching stub reduces the maximum SWR from ted for the one-decade band from 100 MHz 1.28 to 1.12 on the UHF TV band. to 1,000 MHz. The 0.6-octave UHF TV band, from 470 MHz to 710 MHz, is highlighted with a darker line. This is the region where Table 1 we want to match the impedance. An EZNEC .GAM Date Table Converted to .FLP Format for Analysis by Serenade The secret to understanding the behavior of this medium bandwidth discone is to note antdata 100MHz 1000MHz 91 50 S that discone impedance curves aren’t uniform EZNEC data for UHF TV discone antenna created on 2/28/2006. concentric spirals on a Smith Chart, like a di- 100MHz 0.9957904 -34.86269 pole would be. Instead, the impedance curves 110MHz 0.9935989 -38.95737 have a small loop in the middle of every large 120MHz 0.9905544 -43.24265 loop. By varying the cone angle and disk radi- • us, a small loop can be moved to the center of • the Smith Chart. Then, by merely scaling the • dimensions, nearly an octave of bandwidth 980MHz 0.4676752 42.40280 can be slid into the small loop. This yields 990MHz 0.4689465 41.08628 a moderately broadband low-SWR antenna, 1000MHz 0.4697061 39.79027 such as our example discone. These steps can be done in reverse order: first put the UHF TV band in a small loop The .GAM file is formatted to Ansoft’s that EZNEC used when making the output and then move the loop to the center of the .FLP format within Microsoft Word in a few data. Finally, save the file as a text file with Smith Chart by inserting an impedance simple steps. First, delete the header line, the .FLP name extension to a Serenade project matching network at the discone’s feed point. leaving only the data lines. Next, use the folder. The file should look like Table 1 With more work, however, the steps can be text-to-table converter in Word to put the data Once the .FLP file has been saved, we done in the original order, and the impedance into a four column table. Cut the contents of open Serenade SV and define a one-port that matching network eliminated. columns two and three and paste to columns references the file to represent the discone The simplest impedance matching net- three and four, leaving column two empty. antenna. Run a frequency sweep, then use work for the discone model is the 75 Ω open Type the frequency unit “MHz” as the first the report editor in Serenade SV to graph stub shown Figure 12. The stub was designed entry in Column two, and paste it into all cells the antenna impedance on a Smith Chart by to match the antenna to 75 Ω and is made of down the column. Next, do a table-to-text asking for a polar plot of S11 and specify Z 75-Ω transmission line. The stub is inserted conversion, specifying a “space” character or Y coordinates, or both. in a 75-Ω feed line at the proper distance from as the delimiter. Finally, remove the space The discone model’s impedance is pre- the feed point. The stub’s electrical length and between the frequency number and its unit by sented in Figures 10 and 11. Both figures position from the feed point (20.5° and 12.6° a global replacement of “[space]M” with “M.” assume a 75 Ω reference impedance. Figure at 600 MHz) translate to physical lengths of The data lines are now finished. Just add two 10 shows the complex impedance curve on 29 mm and 17 mm times the velocity factor header lines before the data lines, making sure the Smith Chart. For antennas, which are of the transmission line. The network can be to specify “50 S” on the first line to indicate passive loads, the curve bends clockwise constructed by using a 75-Ω coaxial T con- that the data is scattering parameter data ref- as frequency increases. Figure 11 shows nector. Because a physical stub terminates erenced to 50 Ω. This is the same convention the resulting SWR, whose agreement with in a fringing capacitance rather than an ideal

42 Jan/Feb 2007 infinite-impedance open circuit, a real stub portions are included here with permission. Kandoian, A. G., “Three New must be made shorter to achieve the predicted and Their Applications,” Waves and Elec- Notes trons, Vol 1, no. 2, , Feb. 1946, pp 70W-75W, performance. Rather than calculate the fring- 1 The Institute of Radio Engineers (1912-1963) a separate section within Proceedings of the ing capacitance, it’s easy to trim the stub by merged with the older American Institute of IRE, Vol 34. Reprinted in Electrical Commu- measurement during construction. Electrical Engineers (1884-1963) to form the nication, Vol 23, no. 1, Mar 1946, pp 27-34. The impedance matching performance Institute of Electrical and Electronics Engi- Kandoian, A. G., W. Sichak, and G. A. Felsen- of the stub matching network is shown in neers (IEEE) in 1963. The IRE was instru- held, “High Gain with Discone Antennas,” mental in the creation of the Federal Radio Proceedings of the National Electronics Figures 13 and 14. Figure 14 shows before Commission in 1927, which became the and after SWR curves. The matching network Conference, Vol 3, Chicago, Nov. 1947, pp FCC in 1934. 318-328. Reprinted with additional figures in 2 reduces the maximum SWR in the UHF TV Mathematically skilled readers will find the pa- Electrical Communication, Vol 25, no. 2, June band from 1.28 to 1.12. pers by Hahn and Fikioris and by Samaddar 1948, pp 139-147. Although most amateurs think of low and Mokole contain rigorous extensions of Smith, P. D. P., “The Conical Dipole of Wide SWR as important for transmitting, it is also Schelkunoff’s original analysis. Angle,” Journal of Applied Physics, Vol 19, important for receiving digital modulations Steve Stearns, K6OIK, started in Amateur no. 1, Jan 1948, pp 11-23. such as DTV signals. The game here is not Radio while in high school at the height of Tai, C. T., “On the Theory of Biconical Anten- the Heathkit era. He holds an FCC Amateur nas,” Journal of Applied Physics, Vol 19, no. about power transmission. Rather, it is about 12, Dec 1948, pp 1155-1160. avoiding waveform distortion caused by Extra license and a commercial General Radiotelephone Operator license with Radar Tai, C. T., “Application of a Variational Principle to frequency selectivity of the communications Biconical Antennas,” Journal of Applied Phys- endorsement. He previously held Novice, ics, Vol 20, no. 11, Nov 1949, pp 1076-1084. channel. Wideband digital signals hate reflec- st tions, regardless of source. Reflections from Technician, and 1 Class Radiotelephone Leitner, A. and R. D. Spence, “Effect of a Cir- multipath propagation and transmission line licenses. He studied electrical engineering at cular Groundplane on Antenna Radiation,” California State University Fullerton, the Uni- Journal of Applied Physics, Vol 21, no. 10, discontinuities are equally bad. The question Oct 1950, pp 1001-1006. of where reflected power goes is, ultimately, versity of Southern California, and Stanford University, specializing in electromagnetics, Schelkunoff, S. A., “General Theory of Sym- unimportant because communication is about metric Biconical Antennas,” Journal of getting information through, not power. communication engineering and signal pro- Applied Physics, Vol 22, no. 11, Nov 1951, Power transmission is merely a means to a cessing. Steve works at Northrop Grumman’s pp 1330-1332. greater end, not the end in itself. Reflections Electromagnetic Systems Laboratory in San Schelkunoff, S. A., Advanced Antenna Theory, Jose, California, where he developed smart Section 2.21, Wiley, 1952. Refer to Figure should be avoided. 1.18 on p 93. Discones and bicones are better antennas antenna and digital demodulation technology for eliminating interference and is currently Schelkunoff, S. A. and H.T. Friis, Antennas: for receiving HDTV signals than bow-tie or Theory and Practice, Wiley, 1952. flat triangle antennas although the latter are developing ways to design and fabricate meta- Brown, G. H. and D.M. Woodward, “Experimen- better than log periodics and Yagis when materials to control electromagnetic phenom- tally Determined Radiation Characteristics phase distortion is considered. A bicone is ena. He has over 50 professional publications of Conical and Triangular Antennas,” RCA and eight US patents and numerous foreign Review, Vol 13, no. 4, pp 425-452, Dec. easier to design than a discone because you 1952. build two identical cones. The question of patents. Steve is an ARRL Life member, has served as an assistant director of ARRL Pacific Nail, J. J., “Designing Discone Antennas,” Elec- disk size disappears. That’s one fewer vari- tronics, Vol 26, Aug 1953, pp 167-169. ables to get right. Other things to consider Division, and is currently the vice-president Crowley, T. H. and W. Marsh, Discone Type are pattern and . Antennas should of Foothills Amateur Radio Society serving Antennas, technical report 510-13, Ohio be mounted with the correct polarization Silicon Valley. Steve has received numerous State Research Foundation, 30 June 1954. awards for professional and community Wait, J. R., “Electromagnetic Radiation from Con- — vertical for VHF/UHF communication ical Structures,” Chapter 12 in Antenna Theo- signals and horizontal for receiving FM and volunteer activities. He can be reached at [email protected] or [email protected]. ry, Part 1, R. E. Collin and F. J. Zucker (eds.), television broadcast signals. When mounted McGraw-Hill, 1969, ISBN 0070117993. horizontally, the azimuthal gain pattern is like Bibliography Lakshminarayana, Y., Y. R. Kubba, and M. E. that of a horizontal dipole — a figure eight for Engineering literature: Madhusudan, “A Wide Band Discone Anten- low frequencies and increasingly multi-lobed Howe, G. W. O., “The Nature of Electromag- na,” Indian Journal of. Electro-Technology, netic Waves Employed in Radio-Telegraphy Vol 15, no. 2, Mar/Apr 1971, pp 57-59. as frequency increases. At high frequencies, and the Mode of Their Propagation,” The Kadakia, D. R. and J. G. Fikioris, “Monopole a discone’s main lobe lies in the half-space Electrician, 19 Sep 1913, pp 965-969. Antenna Above a Hemisphere,” IEEE Trans- on the cone side of the disk. As frequency Howe, G. W. O., “The Capacity of an Inverted actions on Antennas and Propagation, increases from low to high, the main lobe Cone and the Distribution of its Charge,” Vol 19, no. 5, Sep 1971, pp 687-690. shifts from the plane of the disk toward the Proceedings of the Physical Society of Lon- Spanos, W. M., Broadband Discone Anten- direction of the cone, and minor lobes emerge don, Vol 29, 1917, pp 339-344. na having Auxiliary Cone, US patent no. Shelkunoff, S. A., “Transmission Theory of 3,618,107, 2 Nov 1971. on both sides of the disk. Spherical Waves,” AIEE Transactions, Vol Hahn, R. F. and J. G. Fikioris, “Impedance 57, 1938, pp 744-750. and of Antennas above Acknowledgments: Carter, P. S., “Simple Television Antennas,” Flat Discs,” IEEE Transactions on Antennas I am grateful to my colleagues at Northrop presented at National Convention of IRE, and Propagation, Vol 21, no. 1, Jan 1973, Grumman’s Electromagnetic Systems Labo- San Francisco, Jun 1939. Published in RCA pp 97-100. ratory who were students of the late John Review, Vol 9, Oct 1939, pp 168-185. Woodman, K. F., “Dielectric-Clad Discone,” Schelkunoff, S. A., “Theory of Antennas of Ar- Electronics Letters, Vol 13, no. 9, 28 Apr Daniel Kraus, W8JK, of Ohio State Univer- bitrary Size and Shape,” Proceedings of the 1977, pp 264-265. sity. In particular, I wish to thank Dr A. G. IRE, Vol 29, Sep 1941, pp 493-521; correc- Smith, C. E., C. M. Butler, and K. R. Umashan- Jennetti, KF6FO, Keith Snyder, KI6BDR, tions published in Nov 1941, p 603, and Jan kar, “Characteristics of a Wire Biconical and Jim Peterson, K6EI, for comments and 1943, p 38. Reprinted without corrections in Antenna,” Microwave Journal, Vol 22, no. 9, ideas that contributed to this article. Proceedings of the IEEE, Vol 72, no. 9, Sep Sep 1979, pp 37-40. Parts of this article appeared in the 1984, pp 1165-1190. Refer to Figure 2A with Stutzman, W. L. and G. A. Thiele, Antenna θ 1 or θ 2 equal to π/2. Theory and Design, Section 6.2, Wiley, 1981, newsletter of the Foothills Amateur Radio Kandoian, A. G., Broad Band Antenna, U.S. ISBN 047104458X. Society, an ARRL affiliated club. Those patent no. 2,368,663, 6 Feb 1945. McNamara, D. A., D. E. Baker and L. Botha,

Jan/Feb 2007 43 “Some Design Considerations for Biconical Marsan, L. A. and E. A. Urbanik, Compact Low cone Antenna,” QST, Jul 1975, pp 11-14, 56; Antennas,” IEEE AP-S Int’l Symp. Digest, RCS Ultra-Wide Bandwidth Conical Mono- Feedback, QST, Sep 1975, p 88. Vol 22, Jun 1984, pp 173-176. pole Antenna, US patent no. 7,006,047, 28 Geiser, D., WA2ANU, “An Inexpensive Multiband Rappaport, T. S., Tunable Discone Antenna, Feb 2006. VHF Antenna,” QST, Dec 1978, pp 28-29. US patent no. 4,851,859, 25 Jul 1989. Amateur Radio literature: Geiser, D., WA2ANU, “More on Discone Anten- Austin, B. A. and A. P. C. Fourie, “Characteris- Boyer, J. M., W6UYH, “Discone — 40 to 500 Mc nas,” QST, May 1979, p 44. tics of the Wire Used for Skywire,” CQ, Jul 1949, pp 11-15 & 69-71. White, T. E., K3WBH, “A Discone Antenna for EMC Measurements,” IEEE Transactions on Reprinted in CQ Anthology, Cowan Publish- 10 and 6 Meters and Lo-Band Public Service Electromagnetic Compatibility, Vol 33, no. 3, ing, 1958. Monitoring,” CQ, Jun 1980, pp 74-75. Aug 1991, pp 179-187. Seybold, M., W2RYI, “The Low-Frequency Dis- Orr, W. I., W6SAI, “A 160-Meter Discone Champion, J. R., et al, Portable Rapidly cone,” CQ, July 1950, pp 13-16, 60. Reprinted Antenna,” Ham Radio, Jul 1987, pp 57-58. Erectable Discone Antenna, US patent no. in CQ Anthology, Cowan Publishing, 1958. Miller, D., NZ9E, “A ‘Universal’ VHF/UHF 5,608,416, 4 Mar 1997. Orr, W. I., W6SAI, (ed.), Radio Handbook, 14th Antenna,” QST, Dec 1994, p 75. Samaddar, S. N. and E. L. Mokole, “Biconical ed, “The Low-Frequency Discone,” Editors Krupp, D. A., W8NWF, “Two HF Discone Antennas with Unequal Cone Angles,” IEEE and Engineers, 1956, pp 369-370 in. Antennas,” The ARRL Antenna Compendi- Transactions on Antennas and Propagation, Pappenfus, E. W., WB6LOH, “The Conical um Vol 5, ARRL, 1996, ISBN 0872595625, Vol 46, no. 2, Feb 1998, pp 181-193. : Four-to-One Frequency pp 121-127. Meitzler, W., W. Turney, and L. T. Malek, “Biconical Coverage with a Vertical,” QST, Nov 1966, Todd, M., VK6JMA, “The Discone,” The Inter- Antenna Scans 4.8 to 5.8 GHz,” Microwaves & pp 21-24. national Antenna Collection, G. Brown (ed.), RF, Vol 44, no. 8, Aug 2005, pp 53-61. Wintzer, M., PAØMWI/DJ4GA, “Dipole Passe? RSGB and ARRL, 2003, ISBN 1872309933, Apostolos, J. T., Collapsible Wide Band Width Some Experiments on Discone Arrange- pp 218-219. Discone Antenna, US patent no. 6,967,626, ments,” QST, Oct 1974, pp 15-21. Patterson, R., K5DZE, “A VHF/UHF Discone 22 Nov 2005. Belrose, J. S., VE2CV/VE3DRC, “The HF Dis- Antenna,” QST, May 2003, pp 40-41.

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