The ARRL Antenna CompendiumVolume 1EditorsGerald L. Hall, K1TDPaul Rinaldo, W4RIMaureen Thompson, KA1DYZContributorsThose 31 authors whose materialis published hereinProductionMaureen Thompson, KA1DYZCover DesignSue FaganPublished by theAmerican Radio Relay LeagueNewington, CT USA 06111THE COVER:A fall s u n r i s e s i l h o u e t t e s the antennas of station W 1 A W .(Photo by J e r r y H a l l , K 1 T D )
Copyright1985 byThe American Radio Relay League, International Copyright securedThis work is Publication No. 58 of the RadioAmateur's Library, published by the League.ISBN: 0-87259-019-4
ForewordT h e t o p i c o f a n t e n n a s is o n e o f t h e mostpopular in Amateur Radio literature.The materialthat has been written for amateurs on antennas wouldfill several volumes, and, indeed, s e v e r a l volumesare already available.So popular is the topic thatA R R L Headquarters receives many more antenna manuscripts f o r consideration as feature article material for the journal, QST, than can be published.In the past we have had to turn away good materialbecause of space limitations in the journal.Instead of returning that material to t h eauthors unpublished, why not collect it and publishit in a single volume? With this thought, The ARRLAntenna Compendium was born.Additional materialwas solicited for Volume 1, and you have the resultin your hands.Early in the planning stages, we chose to use theformat of QEX in preparing material for publication.The authors have provided their own camera-ready artwork, and "typesetting" has been done with Apple liecomputers and an NEC-3550 letter-quality printer.This approach was an experiment; we hope you willlike the results.There is a wealth of material between thesecovers, and on a variety of antenna subjects.Ifyou have a serious interest in antenna design orconstruction, you'll likely find something here thatis "right up your a l l e y . "A t this w r i t i n g weanticipate that the Compendium will become quitepopular, and t h a t V o l u m e 2 w i l l be a l o g i c a lfollow-on. We'd appreciate receiving your commentsand suggestions for the next volume.David Sumner, K1ZZExecutive Vice PresidentNewington, CT
ContentsQuad and Loop Antennas8The Sloping Diamond, A Full-Wave Loop for Four Bands the Easy WayDuane R . Sanderson, W0TID11Optimum Gain Boomless QuadHarold T . Mitchell, NJ0ARQ18Bicycle Wheel QuadDave Guimont, WB6LL020Quad Antennas for 80 and 160 MetersWilliam M . Kelsey, N8ET24Gossamer Quad UpdateR . F . Thompson, W30DJ/ZF2CD29The PV4 Quad — A New TwistJohn DeWitt, AI9P41Cubical-Quad Antenna DesignNorris G . Boucher, W3GNRLog Periodic Arrays48A Wide-Band, Low-Z Antenna —Ken Heitner, WB4AKKNew Thoughts on Small Antennas50Development of the W8JF Waveram: A Planar Log-Periodic Quad ArrayJim Fisher, W8JF55A Second-Generation Spiderweb AntennaDick A . M a c k , W6PGLOther Beam Antennas62A Simple Log-Yag Array for 50 MHzJohn J . Meyer, N5JM64Designing X-BeamsBrice Anderson, W9PNE67An HF Phased Array Using Twisted-Wire Hybrid Directional CouplersJames V . Melody, WA2NPJ/KX6JM72LARAE — Line Array of Rotary Antennas in EchelonA . J . F . Clement, W6KPCMultiband Antennas84A Great 10 Through 40 Portable AntennaEdward L . Henry, K0GPD86The G5RV Multiband Antenna . . . Up-to-DateLouis Varney, G5RV
Vertical Antennas92Wiring Up the Old SpruceKris Merschrod, KA2I0G94A Triband Parasitic Vertical Directional ArrayWalter J. Schulz, K30QF101The 5/8-Wavelength Antenna MystiqueDonald K. Reynolds, K7DBAAntennas of Reduced Size108Optimum Design of Short Coil Loaded High-Frequency Mobile AntennasBruce P. Brown, W6TWW116Short Loaded Half-Wave Dipole Design —H. L. Ley, Jr., N3CDRThe Easy WayMiscellaneous Antennas124Dielectric Antennas for the 10-GHz and Higher Amateur BandsDavid Andersen, KK9W127A Crossed-Loop/Goniometer DF Antenna for 160 MetersCharles P. W. Anderson, N4KF133Subsurface Antennas and the AmateurRichard Silberstein, W0YBFAntenna Construction and Installation142A New Approach to the Construction of Large Yagi BeamsArie Bles, VK2AVA144Raising Beam AntennasLawson Young, N4LYGeneral Antenna and Transmission-Line Information148The Horizontal Dipole Over Lossy GroundRobert B. Sandell, W9RXC152Antenna PolarizationGerd Schrick, WB8IPM157Baluns: What They Do and How They Do ItRoy W. Lewallen, W7EL165Available Power, SWR and LoadingDavid T. Geiser, WA2ANU170Mr. Smith's "Other" Chart and Broadband RigsRoger K. Ghormley, W0KK
Quad and Loop Antennas
The Sloping Diamond, AFull-Wave Loop for FourBands the Easy WayDuane R. Sanderson,* W0TID 3735 S. E. Stanley Rd., Tecumseh, KS 66542The full-wave loop antenna has become the subj e c t of increasing interest among antenna experimenters in recent years. Judging by the volume ofquestions and comments I receive on the air, theloop is gaining popularity as an a b o v e - a v e r a g ep e r f o r m e r . A f t e r 34 years as an active licensedamateur in pursuit of "that one great antenna," Ithink I have t r i e d just about all applications ofthe standard quarter and half-wave antenna.My e x p e r i e n c e has shown t h a t f o l d e d - d i p o l eantennas have always performed better for me thanstandard dipoles. The folded dipole is basically afolded full-wave loop. An argument as to which antenna is best is not the point here. I only mentionthis to identify the experimenting trail that led meto an antenna I currently use. I decided my searchfor a better antenna would be in the full-wave loopcategory.the loop. The formula I used for the loop length isthe standard L 1005/f (MHz). I used 142 feet ofn o . 12 g a u g e c o p p e r wire for my loop t h a t Istretched into a vertical delta shape, tying t h ebottom corners to appropriately spaced 4-foot metalfence posts. I could just reach the lower horizontalpart of the delta while standing on the ground. Theappropriate prune-and-tune period took many tripsfrom the rig to the antenna and back again with thebest SWR figure of 1.6:1.Performance was a bit disappointing. Orientation was broadside east and w e s t . Forty-meterdaytime short skip was not as good as on the olddipole, and signal r e p o r t s o f t e n included heavy"QSB" and "fading" comments. Long skip and nighttimeResearch Before ConstructionA review of published a n t e n n a a r t i c l e s , daydreaming and mental pictures was necessary before Ibegan to string wire. Published data on loops statedthat some of their advantages are to provide gainover a dipole, and they are usually quiet even in anoisy environment. More broadbanded than half-wavetypes, they will work on more than one band.These good points are a match for my anteimarequirements. My QTH is in a rural setting withleaky high tension power lines at the front of theproperty. I work both SSB and CW, and wanted anantenna that would work on 40 meters with 15-meterc a p a b i l i t y , and be coaxial line fed. I decided toput up a full-wave loop. Now, what's next?ILoop ShapeD i f f e r e n t handbooks s t a t e t h a t loops can becircular, square, rectangular, delta or diamond. Myuse of this term "diamond" differs from the squarein t h a t t h e two inside d i s t a n c e s of a diamond,between the sets of opposite points, are not equal.It is longer than it is wide.From a construction standpoint, I concluded thedelta was the most practical shape. Only one mast isneeded to support the apex of a vertical delta, andmetal fence posts can be driven into the yard at appropriate places to tie off the two bottom points.It just so happened that I had a 45-foot mastnear the garage with a TV antenna on top. The centerof the 40-meter dipole was attached about one footbelow the TV antenna. The dipole was fed with abalun and a 52-ohrn mini-foam coaxial c a b l e . Ilowered the ends of the dipole and connected theappropriate half-wavelength of wire to them to formFig, 1 —The sloping-diamond loop antenna.
performance was somewhat improved, but not significantly better than the dipole. The delta did notperform well on 20, 15, and 10 meters.A f t e r s e v e r a l weeks of delta operation, Ielected to try another loop shape. Again, the newshape had to work using only one mast for primarysupport, so I pulled the delta into the shape of adiamond and tied the two side points and the lowerpoint to nearby objects. A f t e r pruning and tuning, Ifound the SWR was 1.3:1. 1 was making progress inobtaining a match, at least.Vertical vs HorizontalAt this point my quad loop was a verticaldiamond, broadside to the southeast and northwest.It was fed at the top, using a 1:1 balun and a 52ohm RG-58 mini-foam coaxial cable. The total lengthof the loop wire was approximately 142 f e e t .Daytime reports were fairly good but not spect a c u l a r . However, nighttime reports were significantly better than any wire antenna I have had atthis QTH. The diamond outperformed my half slopers,which are mounted on a 50-foot tower, by at leastone S unit or more.The next few days and evenings were spent on40-meter CW enjoying the short-skip daytime 579reports, and the nighttime 589 to 599 reports fromthe West Coast. The power input was 60 watts.Operation of the loop on 20 CW resulted in ratherpoor performance compared with a 20-meter dipole onthe tower. I concluded my diamond loop to be a good40-meter nighttime long skip and DX antenna.As time progressed, I encountered a few stations in nearby states who were using horizontalquad loops. These stations were consistently loud onthe band in the daytime, and seemed to be morefade-free than others. They seemed to be using ana n t e n n a w i t h h i g h - a n g l e radiation with r e i n forcement from nearby ground reflection, and had theequivalent of a two-element quad pointing straightup.In choosing this antenna for use at my QTH, Irecognized that most of my operating is in the daytime or early evening hours, with late-night DXingan occasional event. This is probably true for themajority of amateurs on 40 meters.I found that, still using the 45-foot TV mastas the top of the diamond, I could pull the loopaway from the vertical plane to nearly horizontal,but with some slope. I placed three metal fenceposts in appropriate locations in the yard as tiepoints for the diamond shape. My horizontal quadbecame a loop sloper with an approximate 30-degreeslope o f f horizontal. See Fig. 1.Once I used the prune-and-tune method on my newantenna, these were the results I obtained.At 7.1MHz no reflected power was measured (1:1 SWR). Thehorizontal-loop impedance was a perfect match to theRG-58 coaxial cable and the broadband characteristics are the best I have ever seen in any of myantenna projects. A check of the SWR on each bandfrom 40 through 10 revealed the following:7.0 MHz7 . 1 MHz1:114.0 MHz1.3:114.1 MHz1.2:11.1:17.2 MHz7.3 MHz1.5:114.2 MHz14.3 MHz1.2:11.2:11.6:121.0 MHz1.8:121.1 MHz1.7:121.2 MHz1.9:121.3 MHz2.0:128.0 MHz1.9:128.1 MHz1.9:128.2 MHz2.3:128.3 MHz2.2:1Does It Work?You bet it does, and it works well on more thanone band. D a y t i m e 40-meter operation is great.Reports received while using 60 watts input areusually 599, and often there are reinforcing comments or questions from the other stations about myantenna. The receiving performance of the slopingdiamond is equally good and demonstrates the quietnature of loops, with low noise and loud signals.Nighttime operation is similar to daytime operationuntil late evening when West Coast stations overtakethe band. At that hour, my half slopers are abouttwo S units better than the loop. This is because oftheir low-angle characteristics. The bonus came whenthe loop was used on 20 meters. The SWR was almostas good as 40 meters, and performance on 20 isgenerally better than my dipole on the tower. Performance on 15 is almost as good as the 3/4-waveslopers on the tower. Performance on 10 has not beenevaluated as of this writing because the band isgenerally dead, a victim of the sunspot cycle.My approach to operating with this antenna isto use a line tuner on 21 and 28 MHz to tune out thesmall amount of reactance present on those bands,and to provide an ideal match to the rig.The ClincherThe sloping diamond was put through a good testa few weeks after it was erected. The world-wide QRPcontest arrived on the calendar and about mid-morning of the first day, I decided to hook my Argonautto the loop and have a go at it. I spent about 2-1/2hours working the 40-, 20-, and 15-meter CW bands. Iworked 50 stations without difficulty. Among my contacts were G4, KH6, KL7, VE, and a good spread ofstations across the U. S. A .This antenna appears to be omnidirectional. Atpresent, I am unable to find holes or blind spots inits performance.Some Construction CommentsA rectangular horizontal loop has four cornersto support, but the use of one mast as the primarysupport keeps things simple. A point on an existingtower, building or other structure can serve equallywell. The mast I use is made of steel conduit,1-3/4-inch diameter at the bottom. Successivelysmaller diameter sections are telescoped together afew inches at each joint with bolts and sheet metalscrews through the overlapping points. I have foundthat sheet metal screws will help maintain a goodelectrical bond between each mast section. The baseof the mast is hinged and set in a small pouredconcrete base f o r s t a b i l i t y . My need f o r masthinging stems from a lot of antenna experimentationat my location and with this setup, I can work aloneto raise or lower the antenna. The mast hinge ismade of two 16-inch pieces of 1-1/2-inch iron pipeset vertically with 10 inches in the concrete and 6inches exposed. The two pipes are about 1-3/4 inchesapart with sufficient space for the mast to setbetween them. All three pipes are then drilled sothat a long bolt can pass through all three, asshown in Fig. 2. The bolt is the hinge or pivot
point. My mast has one top guy on the side oppositethe antenna, and the diamond shape of the antennaforms the equivalent of two other guys.The end product is a 3-guy arrangement, and thestability of the mast is surprisingly good. A housebracket about midway up the mast ties it to theeaves of the roof. This makes the mast rigid andflexproof.SummaryThe unique propagation advantages of a horizontal loop seem to combine, to some degree, withthe propagation advantages of a vertical loop whenthe plane of the loop is sloping. The amount ofground space required for the fence-post anchors isdetermined by the degree to which the constructorpulls the diamond sides apart. My diamond is nearlytwice as long as it is wide. The ARRL Antenna Bookstates that next to a circular loop, a square loopis the most efficient, and rectangular loops orunequal diamonds have some energy cancellation. Myloop is more broadbanded and provides the best matchto 52-ohm coax, when it is shaped as an unequaldiamond. The use of a balun is optional. My use ofbalanced feed stems from my preference for asymmetrical pattern.My experience with this antenna as a slopingloop has produced reports that are considerablybetter than when the loop is hung vertically. Theexception is for late-night long skip where a vertical loop would perform best.My home is surrounded by hilly terrain that is40 feet plus higher than my yard elevation. Amateurs with low lying antenna sites, or at locationssurrounded by tall objects, may find the horizontal or sloping loop to be the best choice. Thosewith large lots may want to try a really big loopand go for an 80-meter loop or one for 160 meters.Soon I will have an 80-meter diamond sloperstrung from a mast on top of one of those hills Imentioned. Listen for me on the bands and help mefind out how well it works!Pig. 2 — A mast hinge i s made of two lengths of1 - 1 / 2 - i n iron pipe s e t in concrete. Their1 - 3 / 4 - i n separation accommodates the s t e e lconduit of the homemade telescoping mast.
Optimum GainBoomless QuadBy Harold T. Mitchell,* N0ARQ 2403 Inca Lane, New Brighton, MN 55112This 2-element beam can be precut for 10, 15,and 20 meters, with provision for 12 and 17 meters.It can also be adjusted for maximum front-to-backratio using mini-stubs.Perhaps you a r e i n t e r e s t e d in a quiet b e a mantenna, superior performance at low heights, singlecoaxial cable feed without an antenna tuner, highquad s t r e n g t h through cross ties, and a one-maninstallation o f a 3-band quad. This a r t i c l e t e l l show those were obtained, plus optimum gain spacingfor each band, and maximum front-to-back ratio adj u s t a b i l i t y . The antenna material cost a total of 75, and a guyed 13-foot roof-top mast was purchasedfor 45.History and BackgroundThe common 2-element 3-band concentric quad waspatented by James C . McCaig of England in 1960.\1 Itused bamboo canes and had an 8-foot boom for 10, 15,and 20 meters. Eighteen years earlier, Clarence C .Moore, W9LZX, had invented the cubical quad antenna to solve corona problems encountered at the 9,500foot altitude site of HCJB in Quito, Ecuador.\i Abeautiful p i c t u r e of f o u r 6 - e l e m e n t HCJB quadsagainst the Andes was shown on the cover of a recentbroadcasting magazine.Y& Quads have withstood thetest of t i m e .The large thin planar elements of either a single or multiband quad have trouble resisting highbending loads. R. Michael Doherty invented a quadwith spreader-reinforced c r o s s a r m s , s t a t i n g in hisp a t e n t , " T h e c h i e f d i s a d v a n t a g e t o cubical quadantennas is their lack of strength and vulnerabilityto high winds and icing conditions.'MIn New Brighton, MN, we are faced with severeweather, plus a r e s t r i c t i v e antenna height o r d i nance. I turned t o the quad for its superior performance when installed at low heights, and pickedup the challenge of designing a strong quad. A t mylocation, the 20-m loop bottom w i r e is only 1/4wavelength above ground, yet the vertical angle ofradiation f o r 20 m e t e r s is s t i l l b e l o w 40 d e grees.VS.I designed this quad with not only performanceand strength in mind, but also simplicity, one-mani n s t a l l a t i o n , and l o w c o s t . P a r a l l e l i n v e n t i o n ,simultaneous development, or redevelopment are notuncommonin history. When almost done with thedetail design based on a local quad, I investigatedthe literature and found the Gem Quad antenna invented by Emerson G. Partridge, VE4RA.\fuZ TheP a r t r i d g e p a t e n t describes a boomless quad withunique fiberglass construction having inherently lowwind r e s i s t a n c e . My design uses Sitka spruce forspreaders. For the ham willing to construct a beamantenna, this design o f f e r s several new advantages,plus a rock bottom price well below that for even abamboo quad (Fig. 1).Why Boomless?Quad wire loops can be square, circular or someintermediate shape, but they have one thing in common: All are planar. In the case of a 3-band concentric quad, the three loops of each element arealso in the same plane. Wind and ice loads produceh i g h b e n d i n g s t r e s s e s in t h e s p r e a d e r s ; highstrength fiberglass tubes, and even vaulting poles,are resorted to.\ Boomless construction and 12 cross ties turnthe quad into a structure with rigidity. Loads canbe shared and mechanical oscillations eliminated. Inaddition, the spreaders are stabilized against sideloads and high bending moments. The boomless quad iss t r o n g t h r o u g h s t r u c t u r a l d e s i g n , and s p r u c espreaders can be used without undue concern. Thequad contains 36 triangles, which are cross-coupledin three dimensions at each vertex.Spiders were designed with 18-degree angles toobtainoptimum gain 0.12-wave spacing f o r eachband.\ A concentric quad only can provide optimumgain for one band, since the boom length determinescommon spacing for all bands.COPffiP.W6.UD-. 8.33'AHTENHA6-7dBd GAINlO 1 TURNING RAS \OS1 11 SQUARE. FETETWIND MVEA5 4 POUMDSMASTSCHEt Ul e H-O PVPEt h r e e s e e m cms&H- P o u n d sFig. 1 — The end view of the roof-mounted15-, and 20-m boomless quad. Each band haswavelength optimum gain spacing.10-,0.12
Precut or Tunable?Table 1 gives precut wire loops and spreaderattachment points for five bands. The emerging 12and 17-meter bands are covered in addition to 10,15, and 20 metersAlfl There are a number of precutloop designs with booms for single band or concentric quads.\11JL2. Precut antennas are convenientbecause construction and tuning steps are eliminated, which may be intimidating or burdensome.However, a considerable performance penalty is paidfor this convenience.R. J. Eckersley, G4FTJ, has stated an excellentcase for antenna tuning, "For working DX it is clearthat good front-to-back ratio is more important thanforward gain — often the limiting factor in copyinga weak signal is interference coming from the opposite d i r e c t i o n . . B i l l Orr, W6SAI, adds weightto the need for quad tuning as he writes, ".thefront-to-back ratio of the array is quite criticalas to stub placement."\14 There are problems withmost tuning stubs as they are relatively long andflimsy affairs, with 34- to 38-inch stub length fora 20-m reflector loop.\l I have added 3 percent to the driver length toobtain precut reflector loops for the boomless quad.This is the accepted relationship that goes back tothe work of Lee Bergren, W0AIW, in 1963.\16r17r18The reflector loop lengths of Table 1 are also usedfor the tuned reflector quad. This permits small12-inch x3-inch mini-stubs rather than long stubsused where driver and reflector loops are initiallyof equal length. A tuned boomless quad is said togive an excellent 25-dB front-to-back ratio on 10and 20 meters, and a very good 20 dB on 15 meters.UaRelays, Baluns, Line Transformers, or Gammas?A boomless quad requires solution of the basicantenna problem — how best to maximize radiatedpower and minimize SWR at the transmitter. Multibandquads have been matched to coaxial feed line byseveral different methods.\2J1A tri-gamma matching system has been devised byJack A. McCullough, W6CHE, and applied to a precut4-element concentric quad with a 30-foot boom.\21 Ihave adapted the tri-gamma match (Fig. 2) to theoptimum-gain boomless quad. A reactance capacitorbalances gammas and the open-wire transmission line,which is the key to the system. The open-wire lineconnects all driver loops and the single coaxialcable from the transmitter.Detail Design and ConstructionThe heart of the boomless quad consists of twoshort steel pipe spider hubs and a pipe axle mast T(Fig. 3). Welded to the hubs are steel angle stockspider arms to support the spreaders. With this huband axle construction, quad elements can be installed one at a time (Fig. 4). The pair of elements then rotate easily in the vertical plane forcomplete cross tying (Fig. 5) prior to bolting tothe hub axle.If a diamond quad is preferred instead of ahorizontal quad, it is only a matter of changinghole locations at the hub axle. For a diamond quad,the signal will be polarized at 45 degrees andcontain both v e r t i c a l and horizontal componentsunless the f e e d point is shifted to an apex. Toobtain a vertically polarized signal, the quad isrotated to obtain feed on a vertical side.CE.NTE.W. OFD R I V E R \ OOPS\oivi1" SPAC\N6 X-2-O" 0 * 0(-Z0 "2.8 MWz.GMNANIArH*50 fINPUTCOA*50-72.JfcI5M-"X -3D"7 5 F (57) "Z-lG MMA3/V* SbPAONG,"TRAusMisstoH l i n e"20 MX 4-0" (."33)tarJlOOpKH-5)1H- MHz. GPMtM3SO( 2 )REACTANCE. C*PAC\TORFig. 2 — The tri-gamma matching system providesimpedance matching and reduces interaction betweenloops. Open-wire transmission line and gamma rodsare 12 AWG solid. Back-to-back alligator clips areused for gamma rod length adjustment during matching. Values in parentheses are for RG-8 coaxialcable and N0ARQ low elevation.Precision assemblies follow from large simplewelding fixtures glued t o g e t h e r f r o m 3/4-inchplywood. Spider accuracy results from a square hubface in contact with the fixture surface (Fig. 6A)and equally spaced 18 degree (5-3/16 inch x 16 inch)ramps to guide the steel angle. Axle T accuracy iso b t a i n e d from a 3/4-inch slot, which l i f t s andaligns the mast pipe for welding to the larger huba x l e p i p e resting in a 1-1/2-inch slot at rightangles (Fig. 6B).FOUR HOLES FOR 3/8" X 1" BOLTSHUB'AXLE. S.SCHEDULE HO P\PESraE. ,TFF\ ANGLE.I ' d e r msl"P\PEXIO»1 r l r L X IUmwt stubODID238" 2 07"\-\Jz. 1.90\%z1.0s -1A"X l-lA"* V " * 1 8 ' 1Fig. 3 — The spider hub and axle mast T are thekey to this boomless quad. Construction allowsseparate installation of each element as well asrotation together in the vertical plane for crosstieing.Sitka spruce was selected for spreader materialfor its strength and low cost. Clear boards withoutknots come from these very tall trees that growalong the coast from Alaska to California. Sitkaspruce is still used f o r propellers and f r a m i n gsmall aircraft. Vertical grain boards are twice asexpensive as flat grain and are unnecessary as theoriginal grain direction is lost when ripped into asquare cross section. Ten 7/8-inch x 7/8-inchspreaders were obtained from two 1-inch x 6-inch x14-foot boards, with several thinner strips l e f to v e r . Each spreader cost 1.76 and weighed 2.4
Fig.theincheach4 — N0ARQ slips the reflector element ontomast T. A 63-inch spruce tie bar supports 12x 3 - i n c h mini-stubs in the bottom center ofreflector loop.Fig. 6 — At A, the spider welding fixture isconstructed on a 2 foot x 2 foot x 3/4-inchplywood base. Evenly spaced 5 3/16-inch x 16-inchramps provide the 18-degree spreader angles. AtB, a hub axle and mast T fixture lifts the 1-8inch mast pipe for welding at right angles to the1-1/2-inch axle pipe.pounds. A sharp saw blade l e f t s l i g h t l y roughsurfaces, which were then primed and painted withlight blue latex house paint to blend with the sky.Sanding or shaping of spreaders is not necessary.Number 12 AWG solid, steel-core copperweld wasused for strength and resistance to stretching. Ifall copper wire were chosen, stranded would be usedfor added resistance to breaking.\22 Spreaders weremeasured according to Table 1 and drilled on thediagonal for the 0.08-inch OD w i r e . It was n i c eworking with solid wood of constant cross sectionrather than thin t a p e r e d b a m b o o o r f i b e r g l a s scylinders. After threading and positioning the wiresat each spreader, wrap wires were added and solderedt o p r e v e n t s h i f t i n g o f t h e s p r e a d e r s on wireloops.\2j S i l i c o n e rubber sealant was applied atd r i l l e d h o l e s t o p r e v e n t water e n t r y and g i v eelectrical insulation.Fig. 5 — N0ART stands on the roof to add 12polyester cross ties by rotating the quad in thevertical p l a n e . Polyester is strong and stretchesvery l i t t l e . It is also highly r e s i s t a n t t o s u n light.Each spreader was designed to butt against itsspider hub and not require adjustment. Spreaderswere fastened to spider arms with glass filamentshipping tape instead of the usual16 stainlesssteel hose clamps (more costly). The shipping tapewas then over-wrapped with black vinyl tape toprotect it from sunlight.It was necessary to plan ahead f o r p l a c i n gvarious gamma-rod spacing insulators on driver loopsbefore closure. To avoid breakage, the copperweldshould be s p l i c e d and s o l d e r e d without sharplybending w i r e s . H e a v y scissors were used to cutout the open-wire line spacers from 1/16-inch Lexan
polycarbonate sheet. Holes can be drilled or punchedin t h i s e x c e l l e n t e l e c t r i c a l insulation, which isalso tough and resiliant. The spacers were laced inplace with nylon cord.\2 This is a very rapid,effective and economical method of building openw i r e l i n e (Fig. 7). It proved especially u s e f u lsince five different spacings were required. As thef i r s t spacer of each reflector loop stub, an egginsulator was used to c a r r y loop tension underload.\2 Turnbuckles are unnecessary in this application, andcan even be undesirable.\22Fig. 8 — A bridle running through a thimble ineach guy wire divides the load between two eye boitsscrewed into the house frame. Two cable clamps areused at each end of the 3/16-inch EHS guy cable. Oneclamp is sufficient for each end of the 3/16-inchbridle cable.Fig. 7 — Coaxial cable input is at the 15-m pointto the tri-gamma matching system. Open-wire linepolycarbonate spacers were laced in place with nylontwine. Variable capacitors used during matching wereremoved, measured, and replaced with silver micafixed capacitors. Coaxial braid and ends were coatedwith silicone rubber sealant to prevent moisturewicking, corrosion and change.Final AssemblyThe boomless quad was assembled on a homebuilt, roof-top mast designed to withstand a 40pound per square foot (100 mi/h) wind load on thesystem.V21 A mast height of 13 feet was chosen as aminimum to be consistent with the 12.8-foot verticalturning radius of the quad. The basic mast was fabricated from two 1-1/2-inch schedule 40 steel pipes.A 10-foot length of pipe weighing 27 pounds was theheaviest item lifted during installation of the quadand mast.A 6-foot sleeve of 2-inch schedule 40 pipe wascentered and fastened with 5/16-inch eyebolts in themiddle of the mast to pin the two 1-1/2-inch pipesections. The main function of the sleeve is to provide additional bending s t r e n g t h in t h a t c r i t i c a llength. The mast, rotator, and tee were preassembled,f o r f i t a n d t h e n f i n i s h e d w i t h R u s t - O l e u rrr1primer and paint before taking sections to the roof forreassembly.Each of three evenly spaced 3/16-inch EHSgalvanized steel guy wires was brought down at a45-degree angle from the eyebolts and terminated ina thimble.\2& A bridle through the thimble (Fig. 8)divided the load of each main cable between two5/16-inch eyebolts screwed into the house frame. Allcable ends were secured wit
41 Cubical-Quad Antenna Design Norris G. Boucher, W3GNR Log Periodi Arrayc s 48 A Wide-Band, Low-Z Antenna — New Thoughts on Small Antennas Ken Heitner, WB4AKK 50 Development of the W8JF Waveram: A Planar Log-Periodic Quad Array Jim Fisher, W8JF 55 A Second-Generation Spiderweb Antenna