UHF Free-Form 4-Bay (FF4) Bowtie Antennas with various sized Variable Double Angle Reflectors (VDAR) analyzed using 4nec2. Essentially ALL dimensions were Optimized using nikiml's Python Scripts, including the Angle of the Reflector's outer "wings".
Pictures of finished FF4's: http://www.avsforum.com/forum/25-hdtv-technical/2483921-northeast-connecticut-mansfield-trees-trees-trees.html#post44801233
a) FF4 + Reflector = 40"x36" (unfolded), same as mclapp's M4 for backfits & comparison purposes, but Reflector is Swept Forward 4.375-in vice 2.5-in. Elements and Feedline are AWG10.
When I changed to AWG8 (w/o reoptimizing), FF4 Gain = 14.3 to 15.3 to 14.8 to 15.6 dBi, with Gain on 470 MHz increasing 0.3 dB, but only 0.1 dB on other freqs. Compare to M4 (10.0"x9.5") Gain = 13.8 to 15.8 to 15.0 dBi and M4 (9.5"x9.0") Gain = 13.3 to 16.0 dBi. So FF4 Gain increased as much as 1 dB on 470 MHz, with higher Gain on low to mid-band channels and about the same on the higher channels, with somewhat lower F/B & F/R Ratios (probably needs a larger Reflector) and same High Gain in Hi-VHF Band:
UHF FF4 Raw Gain = 15.1 dBi +/- 0.4 dB, dropping to 14.0 dBi on 470 MHz, F/B & F/R Ratio Min = 14.8 dB [GOOD] and SWR (300-ohms) under 1.8. Hi-VHF Raw Gain = 8.1 dBi, F/B & F/R Ratio Min = 19 dB [EXCL] and SWR = 16.8 to 15.7 [Excessive].
SUMMARY OF DIMENSIONS FROM 4nec2 FILE (In inches, rounded to nearest 1/8-in): Rbow=0.051 ' Radius of Bowtie Elements (AWG10, not critical) Rfeed=0.051 ' Radius of Feedlines (cAWG10, not critical) Hop=1.0 ' X-Coord Separation of Feedlines at Crossover ZBowII=12.0 ' From Center of INNER Bowtie to Center of INNER Bowtie, Optimizer found 11.99499 ZBowOI=11.0 ' From Center of INNER Bowtie to Center of OUTER Bowtie, Optimizer found 10.91547 BowLeni=11.5 ' INNER Bow Whisker Length (lose some in bend), Optimizer found 11.59459 BowLeno=12.0 ' OUTER Bow Whisker Length (lose some in bend), Optimizer found 11.95864 BSi=1.5 ' INNER Bow Forward Sweep distance at tip of the Whisker, Optimizer found 1.557153 BSo=5.75 ' OUTER Bow Forward Sweep distance at tip of the Whisker, Optimizer found 5.78872 TineSepi=7.375 ' INNER Bow Tine Separation, Optimizer found 7.344971 TineSepo=6.5 ' OUTER Bow Tine Separation, Optimizer found 6.513835 FS=1.75 ' Separation between two FEEDLINE wires, Optimizer found 1.773704 ZCross=2.625 ' From Center of Feedline Cross-Over to Center of OUTER Bowtie, Optimizer found 2.68731
################################################################## b) FF4 + TALLER Reflector = 48"x36" unfolded), Reflector is Swept Forward 3.375-in vice 2.5-in. Elements and Feedline are AWG10. Outer Bowties are now much smaller, at SAME Angle as Inner. Raw Gain increased 0.3 dB on 470 MHz, 1.6 dB more on 698 MHz and eliminated the mid-Band Gain Dip found in the above AWG10 40x36-in Reflector.
UHF Raw Gain = 14.6 (470 MHz) to 16.2 (674 MHz) peaking at 17.1 dBi (698 MHz), UHF F/B & F/R Ratio Min = 14.8 dB [GOOD] and SWR (300-ohms) under 2.1. Hi-VHF Raw Gain = 10.8 to 8.3 dBi, F/B & F/R Ratio Min = 10.9 dB [FAIR] and SWR (300-ohms) = 34 to 23 (Excessive).
SUMMARY OF DIMENSIONS FROM 4nec2 FILE (In inches, rounded to nearest 1/8-in): Rbow=0.051 ' Radius of Bowtie Wires (AWG10, not critical) Rfeed=0.051 ' Radius of Feedline Wires (AWG10, not critical) Hop=1.0 ' Wire Separation at the Feedline Crossover ZBowII=12.0 ' From Center of INNER bowtie to Center of INNER Bowtie, Optimizer found 11.99729 ZBowOI=10.675 ' From Center of INNER Bowtie to Center of OUTER Bowtie, Optimizer found 10.67465 BowLeni=12.875 ' INNER Bow Whisker Length (lose some in bend), Optimizer found 12.86343 BowLeno=8.125 ' OUTER Bow Whisker Length (lose some in bend), Optimizer found 8.124315 BSi=3.5 ' INNER Bow Forward Sweep distance at tip of the Whisker, Optimizer found 3.496068 BSo=2.25 ' OUTER Bow Forward Sweep distance at tip of the Whisker, Optimizer found 2.273594 TineSepi=6.75 ' INNER Bow Tine Separation, Optimizer found 6.813349 TineSepo=3.875 ' OUTER Bow Tine Separation, Optimizer found 3.875966 FS=2.875 ' Separation between two FEEDLINE wires, Optimizer found 2.82885 ZCross=2.375 ' From Center of Feedline Cross-Over to Center of OUTER Bowtie, Optimizer found 2.406892
################################################################## c) FF4 with a TALLER and WIDER Reflector alternative is T.B.D.
EDIT (23Mar2016): Added Dimensioned Drawing for Bowtie portion of FF4+VDAR(48x36) version (b) and replaced associated 4nec2 File with embedded CMD--OPT and CMD--EVAL Commands (vice original *.bat text File).
Date(s): 2 Nov 2013. Album by holl_ands. 1 - 54 of 54 Total. 11483 Visits.
enlarge 174KB, 681x1024 1 UHF Free-Form 4-Bay + DblAnglRefl - OPT Double Angle Reflector = 40-in H x 36-in W 3D View
enlarge 300KB, 865x1024 2 UHF Free-Form 4-Bay + DblAnglRefl - OPT Double Angle Reflector = 40-in H x 36-in W Front View [1 large square = 5-inches] Probably needs a TALLER Reflector.
enlarge 143KB, 422x1024 3 UHF Free-Form 4-Bay + DblAnglRefl - OPT Double Angle Reflector = 40-in H x 36-in W Top View [1 large square = 2.5-inches]
enlarge 103KB, 323x1024 4 UHF Free-Form 4-Bay + DblAnglRefl - OPT Double Angle Reflector = 40-in H x 36-in W Side View [1 large square = 5-inches]
enlarge 86KB, 791x1024 5 UHF Free-Form 4-Bay + DblAnglRefl - OPT Double Angle Reflector = 40-in H x 36-in W 4nec2 File
enlarge 22KB, 791x1024 6 UHF Free-Form 4-Bay + DblAnglRefl - OPT Double Angle Reflector = 40-in H x 36-in W Contents of Python Control *.bat File
enlarge 194KB, 1152x686 7 UHF Free-Form 4-Bay + DblAnglRefl - OPT Double Angle Reflector = 40-in H x 36-in W UHF Raw Gain = 15.1 dBi +/- 0.4 dB, dropping to 14.1 dBi on 470 MHz
enlarge 190KB, 1152x686 8 UHF Free-Form 4-Bay + DblAnglRefl - OPT Double Angle Reflector = 40-in H x 36-in W UHF SWR (300-ohms) Under 1.8
Note MIN at 470 MHz, unlike most 4-Bay's
enlarge 242KB, 1152x686 9 UHF Free-Form 4-Bay + DblAnglRefl - OPT Double Angle Reflector = 40-in H x 36-in W UHF Impedance
enlarge 299KB, 1024x1024 10 UHF Free-Form 4-Bay + DblAnglRefl - OPT Double Angle Reflector = 40-in H x 36-in W Azimuthal Pattern at 470 MHz
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enlarge 178KB, 1152x686 22 UHF Free-Form 4-Bay + DblAnglRefl - OPT Double Angle Reflector = 40-in H x 36-in W Hi-VHF Raw Gain = 8.1 dBi Hi-VHF F/B & F/R Ratio Min = 19 dB
enlarge 205KB, 1152x686 23 UHF Free-Form 4-Bay + DblAnglRefl - OPT Double Angle Reflector = 40-in H x 36-in W Hi-VHF SWR (300-ohm) = 16.8 to 15.7
enlarge 235KB, 1152x686 24 UHF Free-Form 4-Bay + DblAnglRefl - OPT Double Angle Reflector = 40-in H x 36-in W Hi-VHF Impedance
enlarge 301KB, 1024x1024 25 UHF Free-Form 4-Bay + DblAnglRefl - OPT Double Angle Reflector = 40-in H x 36-in W Azimuthal Pattern at 174 MHz
enlarge 303KB, 1024x1024 26 UHF Free-Form 4-Bay + DblAnglRefl - OPT Double Angle Reflector = 40-in H x 36-in W Azimuthal Pattern at 198 MHz
enlarge 306KB, 1024x1024 27 UHF Free-Form 4-Bay + DblAnglRefl - OPT Double Angle Reflector = 40-in H x 36-in W Azimuthal Pattern at 216 MHz
enlarge 156KB, 574x1024 28 UHF Free-Form 4-Bay + DblAnglRefl - OPT Double Angle Reflector = 48-in H x 36-in W 3D View
enlarge 289KB, 746x1024 29 UHF Free-Form 4-Bay + DblAnglRefl - OPT Double Angle Reflector = 48-in H x 36-in W Front View [1 large square = 5-inches] Probably needs a WIDER Reflector.
enlarge 120KB, 343x1024 30 UHF Free-Form 4-Bay + DblAnglRefl - OPT Double Angle Reflector = 48-in H x 36-in W Top View [1 large square = 2.5-inches]
enlarge 96KB, 791x1024 31 UHF Free-Form 4-Bay + DblAnglRefl - OPT Double Angle Reflector = 48-in H x 36-in W 4nec2 File
enlarge 209KB, 768x1024 32 UHF Free-Form 4-Bay [Just the Bowties] FLAT View [Prior to Bowtie Forward Sweep] [1 large square = 5-inches] "[1 large square = 2.5-inches]" "The top measure line that both the Z..." View Comments...
enlarge 95KB, 286x1024 33 UHF Free-Form 4-Bay + DblAnglRefl - OPT Double Angle Reflector = 48-in H x 36-in W Side View [1 large square = 5-inches]
enlarge 194KB, 1152x691 34 UHF Free-Form 4-Bay + DblAnglRefl - OPT Double Angle Reflector = 48-in H x 36-in W UHF Raw Gain = 14.6 (470 MHz) to 16.2 (674 MHz) peaking at 17.1 dBi (698 MHz). UHF F/B & F/R Ratio Min = 14.8 dB.
enlarge 189KB, 1152x691 35 UHF Free-Form 4-Bay + DblAnglRefl - OPT Double Angle Reflector = 48-in H x 36-in W UHF SWR (300-ohm) Under 2.1
enlarge 247KB, 1152x691 36 UHF Free-Form 4-Bay + DblAnglRefl - OPT Double Angle Reflector = 48-in H x 36-in W UHF Impedance
enlarge 298KB, 1024x1024 37 UHF Free-Form 4-Bay + DblAnglRefl - OPT Double Angle Reflector = 48-in H x 36-in W Azimuthal Pattern at 470 MHz
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enlarge 298KB, 1024x1024 47 UHF Free-Form 4-Bay + DblAnglRefl - OPT Double Angle Reflector = 48-in H x 36-in W Elevation Pattern at 698 MHz
enlarge 293KB, 1024x1024 48 UHF Free-Form 4-Bay + DblAnglRefl - OPT Double Angle Reflector = 48-in H x 36-in W Elevation Pattern at 806 MHz
enlarge 182KB, 1152x691 49 UHF Free-Form 4-Bay + DblAnglRefl - OPT Double Angle Reflector = 48-in H x 36-in W Hi-VHF Raw Gain = 10.8 to 8.3 dBi Hi-VHF F/B & F/R Ratio Min = 10.9 dB
enlarge 215KB, 1152x691 50 UHF Free-Form 4-Bay + DblAnglRefl - OPT Double Angle Reflector = 48-in H x 36-in W Hi-VHF SWR (300-ohms) = 34 to 23 is EXCESSIVE
enlarge 241KB, 1152x691 51 UHF Free-Form 4-Bay + DblAnglRefl - OPT Double Angle Reflector = 48-in H x 36-in W Hi-VHF Impedance
enlarge 306KB, 1024x1024 52 UHF Free-Form 4-Bay + DblAnglRefl - OPT Double Angle Reflector = 48-in H x 36-in W Azimuthal Pattern at 174 MHz
enlarge 300KB, 1024x1024 53 UHF Free-Form 4-Bay + DblAnglRefl - OPT Double Angle Reflector = 48-in H x 36-in W Azimuthal Pattern at 198 MHz
enlarge 298KB, 1024x1024 54 UHF Free-Form 4-Bay + DblAnglRefl - OPT Double Angle Reflector = 48-in H x 36-in W Azimuthal Pattern at 216 MHz