Editor
`R. Dean Straw, N6BV
`
`Contributing Editors
`Gerald L. Hall, K1 TD
`Brian Beezley, K6STI
`
`Production
`Shelly Bloom, WB1 ENT
`Sue Fagan
`Steffie Nelson, KA 1 IFB
`David Pingree, N1 NAS
`Dianna Roy
`Joe Shea
`
`180
`
`THE COVER
`Left photo: SKOUX, in Stockholm, Sweden: A 100-ft tower with 5-el
`20-meter beam, a VHF/UHF tower and a 60-ft tower with a log-periodic
`beam for 1 O, 12, 15, 17 and 20 meters. Photo courtesy Henryk Kotowski,
`SMOJHF.
`Right photo: The WOUN antenna farm, La Salle, Colorado. A 160-foot
`rotating tower (left side of photo) provides plenty of room for the four
`beams: 4-el 40-m at 160 ft, 7-el 15-m at 120 ft, another 4-el 40-m at 80 ft
`and anoth er 7-el 15-m at 40 ft. The 85-ft tower holds a 4-el 40-m beam
`at 85 ft. For good measure, the telephone pole at the far right holds an
`8-el 15-m beam at 58 ft. Photo courtesy John Brosnahan, WIJUN.
`Cover design: Sue Fagan
`
`Published by
`
`. • The American Radio Relay League
`
`Newington, CT 06111
`
`Page 1 of 8
`
`Samsung Exhibit 1028
`
`

`

`Copyrlg,hl © 1!194 by
`
`T l1e Ameflela'1 ~Fldio Ral y l.Elagu
`
`Gopyn'glll t;-eooroa undflt 1./111 P1m-AI1iencan
`C:Oll venlJort
`
`I omatlcrnal Cap~r ghrsecured
`
`This Mr~ is pubCJcation ~o. i $ of 11'1a Radio
`An'1at011r'i; !Jhrary, publlshed by Ille League.
`All rigf'llB r<iservad. No parl of 11115 vork ma)'
`be reproduced in any form ,ijxCGpL by vrillan
`p rml!i&Jon or lhe pul'ill her, All rlghua DI
`tmr leitiort ate reserved
`
`Printed In USA
`
`Qued<111 re.i>BrVado:; 'rxiof! los dem I~
`
`lbrary a Corpgr!55 Cat og Card Nu·n !Mir:
`f>S-6966
`
`17111 dl1[011
`sacond Prinl11ig, r 9.94
`
`I l~B ~; 0 0726 -47a.4
`
`ii
`
`Page 2 of 8
`
`

`

`....
`
`Contents
`
`1
`2
`3
`4
`5
`6
`7
`8
`9
`10
`11
`12
`13
`14
`15
`
`Safety First
`Antenna Fundamentals
`The Effects of the Earth
`Selecting Your Antenna System
`Loop Antennas
`Antennas for Limited Space
`Multiband Antennas
`Multielement Arrays
`Broadband Antennas
`Log Periodic Arrays
`HF Yagi Arrays
`Quad Arrays
`Long Wire and Traveling Wave Antennas
`Direction Finding Antennas
`Portable Antennas
`
`Iv
`
`Page 3 of 8
`
`

`

`-
`
`16
`17
`18
`19
`20
`21
`22
`23
`24
`25
`27
`28
`A-1
`719
`
`Mobile and Maritime Antennas
`Repeater Antenna Systems
`VHF and UHF Antenna Systems
`Antenna Systems for Space Communications
`Antenna Materials and Accessories
`Antenna Products Suppliers
`Antenna Supports
`Radio Wave Propagation
`Transmission Lines
`Coupling the Transmitter to the Line
`Transmission-Line and Antenna Measurements
`Smith Chart Calculations
`Appendix
`Index
`
`v
`
`Page 4 of 8
`
`

`

`Broadband Toroidal Baluns
`Air-wound balun transformers are somewhat bulky when
`wound coil balun transformers. Two such baluns are described
`designed for operation in the 1.8- to 30-MHz range. A more
`here.
`compact broadband transformer . can be realized by using
`In Fig 25A, a 1: 1 ratio balanced to unbalanced line
`toroidal ferrite core material as the foundation for bifilar-
`transformer is shown. This transformer is useful in converting
`
`J1
`
`R
`UNBALANCED
`
`T2
`
`b
`
`J5
`
`4R
`BALANCED
`
`J6
`
`R
`UNBALANCED
`
`4:1 RATIO
`
`Fig 25-Schematic and pictorial
`representations of the balun
`transformers. The windings are
`labeled a, b and c to show the
`relationship between the pictorial
`and schematic Illustrations.
`J1, J4-S0-239-type coax
`connectors or similar.
`J2, J3, JS, J6-Steatite feed(cid:173)
`through bushings.
`T1, T2-Wound on CF-123 toroid
`cores (see text).
`
`R ~ UNBALANCED
`
`~:RO'°") CORE
`
`R- BALANCED
`
`,,,...---.--u
`
`0
`
`R- UNBALANCED
`
`R
`BALANCED
`
`T1
`
`a
`
`b
`
`c
`
`a
`
`b
`
`c
`
`1:1 BALANCED TO UNBALANCED
`
`4 :1 BALANCED TO UNBALANCED
`
`(A)
`
`(8)
`
`25-16
`
`Chapter 25
`
`Page 5 of 8
`
`

`

`-
`
`a 52-0 balanced line condition to one that is 52 0, unbalanced.
`Similarly, the transformer will work between balanced and
`unbalanced 75-0 impedances. A 4: 1 ratio transformer is
`illustrated in Fig 25B. This balun is useful for converting a
`208-0 balanced condition to one that is 52 0, unbalanced. In
`a like manner, the transformer can be used between a balanced
`300-0 point and a 75-0 unbalanced line. Both balun trans(cid:173)
`formers will handle 1000 watts of RF power and are designed
`to operate from 1.8 through 60 MHz.
`Low-loss high-frequency ferrite core material is used for
`Tl and T2. The cores are made from Q2 material and are
`0.5 inch thick, have an OD of 2.4 inches, and the ID is
`1.4 inches. The permeability rating of the cores is 40.
`Packaged I-kilowatt balun kits, with winding instructions for
`1: 1 or 4: 1 impedance transformation ratios, are available, but
`use a core of slightly different dimensions. Ferrite cores are
`available from several sources. See Chapter 21.
`
`Winding Information
`The transformer shown in Fig 25A has a trifilar winding
`consisting of 10 turns of no. 14 Formvar-insulated copper
`wire. A 10-turn bifilar winding of the same type of wire is
`used for the balun of Fig 25B. If the cores have rough edges,
`they should be carefully sanded until smooth enough to
`prevent damage to the Formvar wire insulation. The windings
`should be spaced around the entire core as shown in Fig 26.
`Insulation can be used between the core material and the
`windings to increase the breakdown voltage of the balun.
`
`Fig 26- Layout of a kilowatt 4:1 toroidal balun trans(cid:173)
`former. Phenolic Insulating board is mounted between the
`transformer and the Mlnibox wall to prevent short(cid:173)
`circuiting. The board Is held In place. with epoxy cement.
`Cement Is also used to secure the transformer to the
`board. For outdoor use, the Mlnlbox cover can be
`Installed, then sealed against the weather by applying
`epoxy cement along the seams of the box.
`
`J2
`
`75/\
`
`J: C2
`
`A 52- to 75-0hm Broadband Transformer
`Shown in Figs 27 through 29 is a simple 52- to 75-0 or
`75- to 52-0 transformer that is suitable for operation in the
`2- to 30-MHz frequency range. A pair of these transformers
`is ideal for using 75-0 CATV Hardline in a 52-0 system. In
`this application, one transformer is used at each end of the
`cable run. At the antenna, one transformer steps the 52-0
`impedance of the antenna up to 75 0, thereby presenting a
`match to the 75-0 cable. At the station end, a transformer
`is used to step the 75-0 line impedance down to 52 0.
`The schematic diagram of the transformer is shown in
`Fig 27, and the winding details are given in Fig 28. Cl and
`C2 are compensating capacitors; the values shown were
`determined through swept return-loss measurements using a
`spectrum analyzer and a tracking generator. The transformer
`consists of a trifilar winding of no. 14 enameled copper wire
`wound over an FT-200-61 (QI material) or equivalent core.
`As shown in Fig 28, one winding has only half the number
`of turns of the other two. Care must be taken when connecting
`the loose ends so the proper phasing of the turns is
`maintained. Improper phasing will become apparent when
`power is applied to the transformer.
`If the core has sharp edges it is a good idea to either sand
`
`Fig 27-Schematlc diagram of the 52- to 75-0 transformer
`described In the text. C1 and C2 are compensating
`capacitors.
`C1-100 pF silver mica.
`C2- 10 pF, silver mica.
`J1, J2-Coaxial connectors, builder's choice.
`T1-Transformer, 6 trlfilar turns, no. 14 enameled copper
`wire on an FT-200-61 (Q1 material, µ.1 = 125) core.
`The upper winding has one-half the number of turns of
`the other two.
`
`Coupling the Transmitter to the Line
`
`25-17
`
`Page 6 of 8
`
`

`

`75 .{\.
`
`10pF/SM
`
`C1
`100 pF/SM
`
`Fig 28- Pictorial drawing of the 52· to 75-n transformer
`showing details of the windings.
`
`the edges until they are relatively smooth or wrap the core
`with tape. The one shown in the photograph was wrapped
`with ordinary vinyl electrical tape, although glass-cloth
`insulating tape would be better. The idea is to prevent chafing
`of the wire insulation.
`
`Construction
`The easiest way to construct the transformer is to wind
`the three lengths of wire on the core at the same time.
`Different color wires will aid in identifying the ends of the
`windings. After all three windings are securely in place, the
`appropriate winding may be unwound three turns as shown
`in the diagram. This wire is the 75-fl connection point.
`Connections at the 52-0 end are a bit tricky, but if the
`information in Fig 28 is followed carefully no problems should
`be encountered. Use the shortest connections possible, as long
`leads will degrade the high-frequency performance.
`The balun is housed in a homemade aluminum enclosure
`measuring 3 Yi x 3 % x I~ inches. Any commercial cabinet
`of similar dimensions will work fine. In the unit shown in the
`photograph, several "blobs" of silicone seal {RTV) were used
`to hold the core in position. Alternatively, a piece of phenolic
`insulating material may be used between the core and the
`aluminum enclosure. Silicone seal is used to protect the inside
`of the unit from moisture. All joints and screw heads should
`receive a generous coating of RTV.
`
`Checkout
`Checkout of the completed transformer or transformers
`is quite simple. If a 75-fl dummy antenna is available connect
`it to the 75-fl terminal of the transformer. Connect a
`transmitter and SWR indicator (52 fl) to the 52-0 terminal
`of the transformer. Apply power (on each of the HF bands)
`and measure the SWR looking into the transformer. Readings
`should be well under 1.3 to 1 on each of the bands. If a 75-fl
`load is not available and two transformers have been
`
`25-18
`
`Chapter 25
`
`Fig 29-The 52- to 75-n transformers. The units are
`Identical.
`
`constructed, they may be checked out simultaneously as
`follows. Connect the 75-0 terminals of both transformers
`together, either directly through a coaxial adapter or through
`a length of 75-0 cable. Attach a 52-fl load to one of the 52-fl
`terminals and connect a transmitter and SWR indicator
`(52 fl) to the remaining 52-fl terminal. Apply power as outlined
`above and record the measurements. Readings should be
`under 1.3 to 1.
`The transformers in the photo were checked in the ARRL
`laboratory under various mismatched conditions at the
`1500-watt power level. No spurious signals (indicative of core
`saturation) could be found while viewing the MF, HF and
`VHF frequency range with a spectrum analyzer. A key-down,
`1500-watt signal produced no noticeable core heating and only
`a slight increase in the temperature of the windings.
`
`Using the Baluns
`For indoor use, the transformers can be assembled open
`style, without benefit of a protective enclosure. For outdoor
`installations, such as at the antenna feed point, the balun
`should be encapsulated in epoxy resin or mounted in a suitable
`weatherproof enclosure. A Minibox, sealed against moisture,
`works nicely.
`
`Balun Terminations
`A word about baluns in Transmatches may be in order.
`Broadband transformers of the type found in many Trans(cid:173)
`matches are not suitable for use at high impedances.
`Disastrous results can be had when using these transformers
`with loads higher than, say, 300 fl during high-power
`operation. The effectiveness of the transformer is questionable
`as well. At high peak RF voltages (high-Z load conditions such
`as 600-fl feeders or an end-fed random-length antenna), the
`core can saturate and the RF voltage can cause arcs between
`turns or between the winding and the core material. If a
`balanced-to-unbalanced transformation must be effected, try
`to keep the load impedance at 300 fl or less. An airwound
`1: 1 balun with a trifilar winding is recommended over a
`transformer with ferrite or powdered-iron core material.
`The principles on which baluns operate should make it
`obvious that the termination must be essentially a pure
`resistance in order for the proper impedance transformation
`to take place. If the termination is not resistive, the input
`impedance of each bifilar winding will depend on its electrical
`
`Page 7 of 8
`
`

`

`characteristics and the input impedance of the main trans(cid:173)
`mission line; in other words, the impedance will vary just as
`it does with any transmission line, and the transformation
`ratio likewise will vary over wide limits.
`Baluns alone are convenient as matching devices when
`the above condition can be met, since they require no
`adjustment. When used with a matching network as described
`earlier, however, the impedance-transformation ratio of a
`balun becomes of only secondary importance, and loads
`containing reactance may be tolerated so long as the losses
`in the balun itself do not become excessive.
`
`BIBLIOGRAPHY
`Source material and more extended discussion of topics
`covered in this chapter can be found in the references given
`
`below and in the textbooks listed at the end of Chapter 2.
`D. K. Belcher, "RF Matching Techniques, Design and
`Example," QST, Oct 1972, p 24.
`W. Bruene, "Introducing the Series-Parallel Network," QST,
`Jun 1986, p 21.
`T. Dorbuck, "Matching-Network Design," QST, Mar 1979,
`p 26.
`G. Grammer, "Simplified Design of Impedance-Matching
`Networks," in three parts, QST, Mar, Apr and May 1957.
`M. W. Maxwell, "Another Look at Reflections," QST, Apr,
`Jun, Aug, and Oct 1973; Apr and Dec 1974, and Aug 1976.
`B. Pattison, "A Graphical Look at the L Network," QST,
`Mar 1979, p 24.
`E. Wingfield, "New and Improved Formulas for the Design
`of Pi and Pi-L Networks," QST, Aug 1983, p 23.
`
`Coupling the Transmitter to the Line
`
`25-19
`
`Page 8 of 8
`
`