Ch22 9-Element Flat-Loop-Fed (FLF) Yagi (518-524 MHz) analyzed using 4nec2 [see *.nec.doc file below]. See Dr. Hidetsugu Yagi holding an example: https://www.jpo.go.jp/seido_e/rekishi_e/hidetsugu_yagi.htm It is Optimized for 8 MHz Bandwidth (to ensure no problems on the band edges...and if ReScaled Upwards) centered on Ch22 [518-524 MHz].
Dimensions were determined using nikiml's Python Optimization Scripts. Similar to Folded Dipole, except rotated (with SOURCE towards REAR) so Co-Planar with rest of Yagi. ALL X,Y,Z Dimensions Optimized.
Note that nikiml's EVAL function [for Horizontally Polarized signals, listed in summary below] calculates somewhat higher F/B & F/R Ratios than 4nec2 Chart [for TOTAL Gain = Horizontal + Vertical Gains].
Ch22 9-El FLF-Yagi - 300ohm OPT Ch22 Raw Gain = 13.2 to 13.4 dBi, F/B & F/R Ratio Min. = 40.2 dB and SWR (300-ohms) Under 1.7. Forward Sidelobes are quite good, being suppressed about 22 dB on 521 MHz. Note that there is a Deep NULL in the Elevation Pattern, which could be used to advantage to suppress Ground Bounce using an Antenna Tilter to aim the Antenna somewhat UPWARDS. BOOM LENGTH = 1019-mm, and is UNCONSTRAINED.
Compare to Alternative Designs for similar 9-El Yagis: use pull-down Navigation Menu above:
Ch22 9-El FD-Yagi - 300ohm OPTimized: Ch22 Raw Gain = 12.7 to 12.9 dBi, F/B & F/R Ratio Min. = 26.4 dB and SWR (300-ohms) Under 2.2.
Ch22 9-El FD-Yagi - 300-ohm K7MEM: Ch22 Raw Gain = 13.3 to 13.4 dBi, F/B & F/R Ratio Min. = 14.3 dB and SWR (300-ohms) = Under 1.4. BOOM LENGTH = 1045-mm (41-1/8 inches).
Ch22 9-El FD-Yagi - 75-ohm MTM Scientific: Ch22 Raw Gain = 11.5 to 11.4 dBi, F/B & F/R Ratio Min. = 17.0 dB and SWR (75-ohms) = 3.3 to 5.0 is EXCESSIVE. BOOM LENGTH = 760-mm.
A Yagi has about the SAME Gain whether driven by a Stick Dipole or a conventional Folded Dipole: http://photos.imageevent.com/holl_ands/yagis/k6sti//Hi-VHF%205-El%20K6STI%20SweptDE%20Yagi%20%20-%20Compare%20OrigandRevAandFD%20Gain.jpg Or use Pull-Down Menu above to Navigate to Analysis of my Optimized Hi-VHF 5-El FD-Yagi vs Stick Dipole Yagi Optimized by K6STI.
HOWEVER, when the additional Element in the Flat-Loop-Fed Yagi is rotated to be Co-Planar, it becomes ONE MORE ELEMENT that can add Gain to the Traveling Wave Signal....it ALSO makes the Yagi LONGER, which we've learned also indicates MORE GAIN....so perhaps we should call this a 10-El Yagi, where the second and third Elements happen to be interconnected at their extremities, forming a Loop.
Note that Flat-Loop-Fed (FLF) Yagi's date back as "PRIOR ART" at least as early as 1940's. Justin Johnson (G0KSC) has (FWIW) Copyrighted some "similar" Loop Fed Array (LFA) Yagis, designed to have a VERY LOW IMPEDANCE [under 50-ohms], but until he has an approved PATENT, it's up in the air as to WHAT UNIQUE FEATURE(S) make it an LFA. More info on this subject: http://www.hamradio.me/antennas/loop-fed-array-lfa-planar-yagi-uda.html
BTW: This Random Optimization Search found Circumference = 51.1-cm [wavelength = 586 MHz] which is NOT one-wavelength at 512 MHz CM [57.58-cm] or anywhere else in the desired 518-524 MHz Band.
Dimensions incl. Min-Max Search Range (all in cm) from below 4nec2 Text File [Variable SYmbol Statements]:
' Cumulative Element Spacings (cm): [May round all Dimensions to nearest 0.1-cm] SY S1=0 SY D2=3.482158' 1, 20 SY S2=S1+D2 SY D2F=1.001045' 1, 20 SY S2F=S2+D2F' LFA LOOP FORWARD ELEMENT [LOOP Spacing in Preceeding] SY D3=2.981495' 1, 20 SY S3=S2F+D3 SY D4=13.40711' 2, 20 SY S4=S3+D4 SY D5=16.09583' 2, 20 SY S5=S4+D5 SY D6=7.782681' 2, 20 SY S6=S5+D6 SY D7=19.70989' 2, 20 SY S7=S6+D7 SY D8=18.18249' 2, 20 SY S8=S7+D8 SY D9=19.24685' 2, 20 SY S9=S8+D9 ' ' Element Lengths (cm): SY L1=28.79224' 15, 40 SY L2=24.55138' 15, 40 SY L3=26.15635' 15, 40 SY L4=24.56356' 15, 40 SY L5=21.93556' 15, 40 SY L6=22.78706' 15, 40 SY L7=23.34455' 15, 40 SY L8=23.2712' 15, 40 SY L9=19.78836' 15, 40 ' ' Z-Coord Distance of Yagi above & below Center line: SY Zyag=0.0 ' Z-Coord Distance of FLF Loop ELement above or below Center line: SY Zloop=0.0 SY Relem=0.3175 ' Yagi Passive Element Radius (in cm for 1/4-in O.D.) SY RACT=Relem ' Yagi Active Element Radius (in cm for 1/4-in O.D.)
' Width between Long Elements in Folded Dipole: [ALSO ALLOWS FOR SQUARE/RECTANGULAR LOOP DRIVERS] SY FW=6.35546' 1, 16 SY FD=FW/2 ' Distance between Center of Boom and Folded Dipole Element SY Gap=2.5 ' Feedpoint Gap (in cm for 1-in Gap)
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