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A HOMEBREW MULTIBANDSMALL SPACE ANTENNA10M-12M-15M-18M-40M-80MAll In One Package!Jerry Wright– NK2CNovember 12, 2020
DESIGN CONSIDERATIONS SMALL FOOTPRINT FAIRLY UNOBTRUSIVE REQUIRE FEW HIGH SUPPORTING TREES ORMASTS MULTIPLE BANDS, 10M THRU 80M SINGLE FEEDLINE USABLE WITH AN ONBOARD TRANSCEIVER TUNER MODERATE COST ( 150, Not Incl. Coax)RADIO AMATEURS OF GREATER SYRACUSE
SETTLED ON VERTICALVARIATIONS REQUIRE A GROUND RADIAL SYSTEM REQUIRE SOME SORT OF MULTI-BAND APPROACHRADIALFIELD¼ WAVEVERTICAL20M2 BANDVERTICALS10/15 & 12/17INVERTEDL40M2 BANDINVERTED L 80MPLAN IS TO FEED MULTIPLE VERTICALS AT ONE POINTJUST LIKE FEEDING THE COMMON FAN DIPOLERADIO AMATEURS OF GREATER SYRACUSE
RADIAL FIELD – OH DEAR!! RADIAL FIELDS HAVE ALWAYS STOPPED ME FROMPLAYING WITH VERTICALS BUT IT IS REALLY VERY SIMPLE, JUST TAKES TIME WHAT I DID: PURCHASED A RADIAL PLATE ON EBAY BUILT A COAX FEED BOX USING 4”X4”X2” WATERPROOFJUNCTION BOX DRILLED AN 18” DEEP HOLE WITH A 1-7/8” DIA. DIRTAUGER CEMENTED A 3 FT, 1-1/4” SCHED 40 GALVANIZED PIPE,18” DEEP – USE A LEVEL! CLAMPED ON THE PLATE AND INSTALLED 25 X 20FTTHHN WIRES CLIPPED TO THE GROUND WITH REBARWIRE CLIPSRADIO AMATEURS OF GREATER SYRACUSE
GROUND PLATE INSTALLATIONRADIAL PLATE - 42 (incl ship)JUNCTIONBOXRADIAL PLATE WITH SOME OF THE RADIAL WIRESTEMPORARILY CLAMPED TO TOP OF GROUND PIPERADIO AMATEURS OF GREATER SYRACUSE
ANTENNA PLAN - SCHEMATIC20M MAST 40M80M12M/17M10M/15M RADIO AMATEURS OF GREATER SYRACUSE20M MAST IS AL CAMOMATL, BUT COULD BE PVCPIPE W/WIRE, OR FENCETOP RAILELEMENTS ARE MOUNTEDON PVC STAND-OFFSFROM 20M ELEMENTELEMENTS CAN BE THHNWIRE OR ANYCONDUCTIVE MATL.I USED 1/8” AL WELDROD SECTIONS JOINEDWITH CLIPS THAT I“SOLDER CAST” ANDENCASED IN HEATSHRINK TUBING.BLOCKING COILS SHOWNARE WOUND TO SPECIFICµH VALUESMAXIMUM CURRENT ISAT THE BASE .
HOW TO RESONATE 2 BANDSON ONE ELEMENT COILS CAN BE USED TWO WAYS ON AN ANTENNAELEMENT THEY CAN BE USED TO SHORTEN A SINGLE BANDELEMENT. LOTS OF DETAIL ON THIS APPROACHCAN BE FOUND AT WWW.K7MEM.COM OR THEY CAN BE USED ON A TWO BAND ELEMENTTO ALLOW RESONANCE ON A HIGHER FREQUENCYBY BLOCKING RF AT THE RESONANT LENGTH. THELOWER FREQUENCY IS NOT BLOCKED AND CANTHEN RESONATE USING THE FULL ELEMENT WITHAN EXTENSION (STINGER) EXAMPLEFEED40M ELEMENTCOILRADIO AMATEURS OF GREATER SYRACUSE80M STINGER
CALCULATING THE INDUCTANCEOF A BLOCKING COIL TO EFFECTIVELY BLOCK, WE NEED A REACTANCEOF 3500Ω. PICK A DESIGN TARGET FREQUENCY INDUCTIVE REACTANCE CALCULATORS CAN BEFOUND ONLINE: – ONE SUCH SITE IS: CTANCE-CALCULATOR.ASPX. IN THIS CASE YOU ENTER THE DESIREDFREQUENCY AND A GUESSED INDUCTANCE ANDYOU WILL GET A CALCULATED REACTANCE.IUSED 7.150 MHZ AND 90 µH WHICH GIVES AREACTANCE OF 4048Ω.RADIO AMATEURS OF GREATER SYRACUSE
ANTENNA DESIGN TARGETS THE MAIN ANTENNA SUPPORT WILL BE A MASTRESONANT ON 20 M AT 14.2 MHZ THE 10/15M ELEMENT WILL TARGET 28.7 & 21.2MHZ. THIS WILL REQUIRE A 19µH COIL THE 12/17M ELEMENT WILL TARGET 24.93 & 18.11MHZ. THIS WILL REQUIRE A 22µH COIL THE 40/80 ELEMENT WILL TARGET 7.15 & 3.55MHZ. THIS WILL REQUIRE A 90µH COILRADIO AMATEURS OF GREATER SYRACUSE
CALCULATING THE COIL TURNSFOR A GIVEN INDUCTANCE I DECIDED TO USE 1” PVC AS A COIL FORM WHICHHAS AN OUTER DIAMETER OF 1.315” I CHOSE 16AWG ENAMELED WIRE (.052” DIA.)FOR THE WINDING. THERE ARE CALCULATORS WHICH WILL DEFINEHOW MANY TURNS ARE NEEDED FOR 90 µH OFINDUCTANCE. e-calculator.aspx. HERE YOU ENTER THE GUESSED TURNS, COILDIAMETER AND WINDING LENGTH RELATED TOGUESSED TURNS (TURNS X DIA.), AND YOU WILLGET A CALCULATED INDUCTANCE.RADIO AMATEURS OF GREATER SYRACUSE
COIL BUILD CRITERIA NEEDED 40/80 METERS: 90µH TARGET 1.5” OD, 4.8” L, 94 TURNS 10/15 METERS: 19µH 1.5” OD, 1.50” L, 27 TURNS 12/17 METERS: 22µH 1.50” OD, 1.65” L, 30 TURNS I FOUND THAT I NEEDED A FEW EXTRATURNSWOUND ON FORM& TESTEDCOATED WITHLIQUID TAPERADIO AMATEURS OF GREATER SYRACUSEWRAPPEDWITH TAPE
CONSTRUCTION DETAILS 20M MAST AND SUPPORT FOR OTHERELEMENTS20M AL MAST INSULATED FROM GROUND BY ATTACHING TOA PVC PIPE WITH STAINLESS HOSE CLAMPS.PVC PIPE THEN DROPS OVER THEGALVANIZED GROUND PIPE. OTHER ELEMENTS ARE SUPPORTED ON 12”PVC STANDOFFS, HOSE CLAMPED TO MASTPVC SUPPORT24” LENGTHS ARE CUTWITH 2’ DIA. HOLE SAWNOTCHES ARE BANDSAWED FOR CLAMP BANDSRADIO AMATEURS OF GREATER SYRACUSE
CONSTRUCTION VIEWS22 µH COILELEMENT STANDOFFSRADIO AMATEURS OF GREATER SYRACUSE
CONSTRUCTION VIEWS20M MAST LASHED TOPVC PIPE INSULATIORAT RADIAL PLATE12/17M ELEMENT TOP& STANDOFFRADIO AMATEURS OF GREATER SYRACUSE
CONSTRUCTION VIEWS90µH COIL/STINGERELEMENT SOLDER CAST JOINTSRADIO AMATEURS OF GREATER SYRACUSE
INITIAL TUNING APPROACH INITIAL ELEMENT GUESSES ARE CALCULATED USINGTHE STANDARD DIPOLE CALCULATION:L(ft) 468/f (MHz) DIVIDED BY TWO SO: 40M 32.75 FT (80M STINGER GUESSED AT 10FT) 20M 16.5 FT (USED 17.3 FT, HARD TO LENGTHENMAST) 12M 9.6FT (17M STINGER GUESSED AT 2FT) 10M 8.20 FT (15M STINGER GUESSED AT 2FT) ELEMENTS WERE CUT 1ST, COIL ADDED ANDSUSPENDED OVER GROUND SYSTEM ON AFIBERGLASS POLE WITH A PULLEY. BASE ELEMENTS WERE TUNED TO MINIMIZE SWRNEAR DESIRED RESONANT FREQUENCY START WITH THE 20M MASTRADIO AMATEURS OF GREATER SYRACUSE
FINAL TUNING APPROACH FINAL TUNING IS AN ITERATIVE PROCESS DONEWITH FULL ANTENNA ASSEMBLED THE ELEMENTSINTERACT! FORTUNATELY THE ANTENNA IS LIGHT AND CAN BELIFTED ON AND OFF THE GROUND SYSTEM EASILY. TUNING THE STINGERS IS VERY TOUCHY AND ACHANGE IN STINGER LENGTH MAY AFFECT THE BASEELEMENT. TRIM JUDICIOUSLY!!! FINAL STINGER LENGTHS WERE: 80M ̴ 8’ 17M 2” 15M 2”RADIO AMATEURS OF GREATER SYRACUSE
SWR CURVES20 METERS32.521.511414.114.214.3RADIO AMATEURS OF GREATER SYRACUSE14.4
SWR CURVES10 METERS32.521.5127.52828.529RADIO AMATEURS OF GREATER SYRACUSE29.530
SWR CURVES15 METERS32.521.5120.92121.121.221.3RADIO AMATEURS OF GREATER SYRACUSE21.421.5
SWR CURVES12 METERS32.521.5124.8924.94RADIO AMATEURS OF GREATER SYRACUSE24.99
SWR CURVES17 METERS2.521.510.5018.0518.118.15RADIO AMATEURS OF GREATER SYRACUSE18.2
SWR CURVES NEXT WAS THE 40M/80M ELEMENT SURPRISE! I COULD NOT GET A MEANINGFULDIP LOWER THAN 5.5/1 ANYWHERE!!! I LEARNED THAT ANTENNAS IN A YARD TALKTO EACH OTHER. I HAVE A 40 M EFHW VERTICAL 25 FT AWAY,PERHAPS OVER A PORTION OF THE NEWRADIAL FIELD. TURNS OUT, A YARD FULL OF ANTENNAS ISONE BIG ANTENNA! SO WE WENT TO A 30M/80M ELEMENT!!! 30M ELEMENT WAS CUT 23 FT TO INDUCTORRADIO AMATEURS OF GREATER SYRACUSE
SWR CURVES30 METERS32.521.5110.0810.110.1210.14RADIO AMATEURS OF GREATER SYRACUSE10.16
SWR CURVES80 METERS3.532.521.52/1 BANDWITH 60 KHZ3/1 BANDWIDTH 90 KHZ10.503.53.523.543.56RADIO AMATEURS OF GREATER SYRACUSE3.583.6
RESONANCE IS FINEBUT DOES IT GET OUT? I USED REVERSE BEACON NETWORK TOSEE HOW THE ANTENNA PROPOGATESON EACH BAND WWW.REVERSEBEACON.NET SENT OUT 26 WPM CQ BLASTS FORABOUT 2 MINUTES THEN CHECKED WHO HAS HEARD ME PLOTTED RESULTS USING GRIDSQUARES AND : http://lcbsweden.com/wwwsm7lcb/maps/qso map/index.htmRADIO AMATEURS OF GREATER SYRACUSE
80 METERS PROPAGATION MAPEuropeTHIS IS NOT AN NVIS ANTENNARADIO AMATEURS OF GREATER SYRACUSE
30 METERS PROPAGATION MAPEuropeRADIO AMATEURS OF GREATER SYRACUSE
20 METERS PROPAGATION MAPEuropeRADIO AMATEURS OF GREATER SYRACUSE
17 METERS PROPAGATION MAPEuropeRADIO AMATEURS OF GREATER SYRACUSE
15 METERS PROPAGATION MAPEuropeRADIO AMATEURS OF GREATER SYRACUSE
80M CW – 3AMRADIO AMATEURS OF GREATER SYRACUSE
80M CW – 12NRADIO AMATEURS OF GREATER SYRACUSE
30M CW – 3AMRADIO AMATEURS OF GREATER SYRACUSE
30M CW 12NRADIO AMATEURS OF GREATER SYRACUSE
20M CW – 12NRADIO AMATEURS OF GREATER SYRACUSE
FINAL COMMENTS ANTENNAS TALK TO EACH OTHER THIS IS REALLY 4 SEPARATE ANTENNAS BUILDING A RADIAL FIELD GIVES LOTS OF OPTIONS 2 BAND 40M/80M 22 FT VERTICAL 20 FT HORIZONTAL 33 FT VERTICAL 10 FT HORIZONTAL 2 BAND 15M/20M 22 FT VERTICAL 6 FT HORIZONTAL ANTENNAS CAN BE HUNG OFF THE SIDE OF TOWERS ORYOU CAN UTILIZE A TOWER FOR THE FIRST ELEMENTAND THEN RUN A WIRE OUT FROM THERE. CAN UTILIZE WIRES WITH NON-CONDUCTIVE MASTS YOU GET THE IDEARADIO AMATEURS OF GREATER SYRACUSE
QUESTIONS?RADIO AMATEURS OF GREATER SYRACUSE
20m mast 40m matl, but could be pvc 10 m/ 15 m from m 80m 20m mast is al camo pipe w/wire, or fence top rail elements are mounted on pvc stand-offs 20m element elements can be thhn wire or any conductive matl. i used 1/8” al weld rod sections joined with clip
