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holl_ands | Home > Multi-Bay Bowtie Antennas > UHF 4-Bay Bowties with Reflector > Browse:Ch22 FF4 4-Bay Bowtie + DARNEW UHF Free-Form 4-Bay + FlatScreenReflUHF Free-Form 4-Bay + DblAnglReflUHF FF4 SingleAngleRefl - DeepSidelobesUHF M4 (10x9.5) Super-4-Bay+DARUHF M4 (9.5x9.0)+DAR Flat vs Swept BowsM4 (9.5x9.0)+DAR Flat v Swept BowsM4 (9.5x9) + Various FLAT Refl. WidthsM4 (9.5x9.0) + 40x34 FLAT Refl at 5-inUHF M4 (9.5x9.0) 4-Bay+FLAT Grid at 5.5"UHF M4 (9.5x9.0) 4-Bay+FLAT Grid at 16"M4 (9.5x9) + Various Number of RRs - OPTUHF KosmicSuperQuad+DAR FlatvsSwept BowsUHF Actual CM4221 Flat Bows & ReflectorUHF CM4221a.ez.nec Flat Bows & ReflectorUHF CM4221HD (Hacked) - 16 ReflRodsUHF CM-4221HD - 10-in WhiskersUHF CM4221HD (Hacked) + Director RodsCM4221HD (Hacked) + Stub FilterAntennacraft U-4000 - 9 Reflector RodsA-D Old DB-4 4-Bay Bowtie with Reflector
UHF FF4 SingleAngleRefl - DeepSidelobes UHF Free-Form 4-Bay (FF4) with Single Angle Reflector providing Deep Sidelobes on lower Frequencies was analyzed using 4nec2. I haven't (yet) figured out how to use nikiml's Optimizer to minimize Gain on one Azimuthal Angle while ALSO maximizing Gain in the Forward direction (if it is even possible), so the fol. might not be an "Optimum" solution. I MANUALLY tried a bunch of things for FF4 with Double and Single Angle Reflectors. I ended up with the fol. TWO designs which have VERY DEEP SIDELOBES on 470 MHz (at 45-deg away from Forward), which decreases in depth on the higher frequencies. Raw Gain also drops off on the higher frequencies. The key was to decrease the Reflector Sweep to only 2-inches. ================================== a) The first alternative started with FF4+VSAR, where ALL Variables were Optimized, including the Reflector Bend Depth (i.e. Angle) and THEN manually varying the Bend Depth for best Sidelobe on 470 MHz: Gain in the Null is -16.9 dB and 30-deg away from the Null the Gain is 12.6 dB, for a TOTAL Suppression of 29.8 dB. However there is significant Loss on higher UHF Channels, accompanied by a reduction in Sidelobe Depth. ==================================== b) The second alternative started with the 2-in Bend Depth determined above and then Re-Optimized the remaining Variables to Maximize Gain throughout the UHF Band.  This resulted in Deep Sidelobe Nulls all across the UHF Band. UHF Raw Gain = 14.2 to 17.3 dBi, F/B & F/R Ratio Min. = 15.7 dB and SWR (300-ohms) under 2.3. It is possible that a more exhaustive search could uncover a somewhat "better" alignment... PS: For some unknown reason, I was unable to generate Hi-VHF Band Performance using either 4nec2 or nikiml's EVAL function....but it's probably similar to alternative (a) due to similarity of Dimensions. ADJUSTING REFLECTOR BEND DEPTH TO MOVE FREQUENCY OF MAX NULL DEPTH[/COLOR][/B] The Bend Depth in the above FF4+VSAR can be adjusted to move the Max Null Depth to the desired Channel Frequency, as shown in the fol. table.  If even deeper Nulls are needed in the upper frequency band, the FF4 would need to be Re-Optimized with this in mind: Reflector Bend Depth is the difference between the X-Coord locations at the Center and the Outer Edges. FF4+VSAR: SIDELOBE NULL RAW GAIN & ANGLE AWAY FROM MAX BEAM, For Various Reflector BEND DEPTHS:   FREQ: 470      530     590     650     698     758     806 MHz BEND: 1.0-in  -16.7   -10.4   -3.9    -0.6     1.8     1.8     4.6  dBi        45-deg  40-deg  35-deg  35-deg  30-deg  25-deg  20-deg 1.5-in  -10.6   -20.5   -7.1    -2.7     0.8     0.6     4.0  dBi        45-deg  40-deg  35-deg  30-deg  30-deg  25-deg  20-deg 2.0-in  -7.0    -21.2   -7.1    -2.7     1.5    -1.6     4.0  dBi        40-deg  40-deg  35-deg  30-deg  30-deg  25-deg  25-deg 2.5-in  -4.4    -13.3   -18.9   -10.7   -0.7    -2.2     2.2  dBi        45-deg  40-deg  35-deg  30-deg  25-deg  25-deg  20-deg 3.0-in  -2.3    -8.4    -16.4   -18.4   -2.9    -3.7    -0.9  dBi        45-deg  40-deg  35-deg  30-deg  25-deg  25-deg  20-deg 3.5-in  -0.6    -5.3    -10.3   -16.3   -5.2    -5.3    -0.7  dBi        45-deg  40-deg  35-deg  30-deg  25-deg  25-deg  20-deg 4.0-in  -0.8    -3.0    -6.6    -10.1   -7.2    -6.8    -2.6  dBi        45-deg  40-deg  35-deg  30-deg  25-deg  25-deg  20-deg EDIT (17Jul2015): Added Second Alternative, with Good Frequency Response and Deep Sidelobe Nulls all across UHF Band (470-698 MHz). EDIT (20Jul2015): Added Null Depth Gain vs Reflector Bend Depth Chart. Date(s): 25 Jun 2015. Album by holl_ands. 1 - 36 of 36 Total. 3013 Visits.
enlarge 191KB, 752x1024 1 UHF FF4 SingleAngleRefl - DeepSidelobes 3D View enlarge 307KB, 829x1024 2 UHF FF4 SingleAngleRefl - DeepSidelobes Front View [1 large square = 5 inches] enlarge 149KB, 447x1024 3 UHF FF4 SingleAngleRefl - DeepSidelobes Top View [1 large square = 2.5 inches] enlarge 182KB, 1024x741 4 UHF FF4 SingleAngleRefl - DeepSidelobes UHF Raw Gain = 14.7 to 15.5 to 12.0 dBi UHF F/B & F/R Ratio Minimum = 8.3 dB enlarge 193KB, 1024x741 5 UHF FF4 SingleAngleRefl - DeepSidelobes UHF SWR (300-ohms) is Under 2.4 enlarge 228KB, 1024x741 6 UHF FF4 SingleAngleRefl - DeepSidelobes UHF Impedance enlarge 304KB, 1024x1024 7 UHF FF4 SingleAngleRefl - DeepSidelobes Azimuthal Pattern at 470 MHz enlarge 300KB, 1024x1024 8 UHF FF4 SingleAngleRefl - DeepSidelobes Azimuthal Pattern at 530 MHz enlarge 305KB, 1024x1024 9 UHF FF4 SingleAngleRefl - DeepSidelobes Azimuthal Pattern at 590 MHz enlarge 302KB, 1024x1024 10 UHF FF4 SingleAngleRefl - DeepSidelobes Azimuthal Pattern at 650 MHz enlarge 301KB, 1024x1024 11 UHF FF4 SingleAngleRefl - DeepSidelobes Azimuthal Pattern at 698 MHz enlarge 301KB, 1024x1024 12 UHF FF4 SingleAngleRefl - DeepSidelobes Azimuthal Pattern at 758 MHz enlarge 289KB, 1024x1024 13 UHF FF4 SingleAngleRefl - DeepSidelobes Azimuthal Pattern at 806 MHz enlarge 102KB, 791x1024 14 UHF FF4 SingleAngleRefl - DeepSidelobes 4nec2 File Includes Summary of Dimensions enlarge 123KB, 421x1024 15 UHF FF4 SingleAngleRefl - DeepSidelobes Side View [1 large square = 5 inches] enlarge 176KB, 1024x741 16 UHF FF4 SingleAngleRefl - DeepSidelobes Hi-VHF Raw Gain = 8.7 to 8.6 dBi Hi-VHF F/B & F/R Ratio Minimum = 10.5 dB enlarge 191KB, 1024x741 17 UHF FF4 SingleAngleRefl - DeepSidelobes Hi-VHF SWR (300-ohms) = 24.4 to 16.5 enlarge 216KB, 1024x741 18 UHF FF4 SingleAngleRefl - DeepSidelobes Hi-VHF Impedance enlarge 305KB, 1024x1024 19 UHF FF4 SingleAngleRefl - DeepSidelobes Azimuthal Pattern at 174 MHz enlarge 304KB, 1024x1024 20 UHF FF4 SingleAngleRefl - DeepSidelobes Azimuthal Pattern at 198 MHz enlarge 304KB, 1024x1024 21 UHF FF4 SingleAngleRefl - DeepSidelobes Azimuthal Pattern at 216 MHz enlarge 196KB, 708x1024 22 UHF FF4 SingleAngleRefl - BetterSidelobes 3D View enlarge 331KB, 932x1024 23 UHF FF4 SingleAngleRefl - BetterSidelobes Front View [1 large square = 5 inches] enlarge 141KB, 426x1024 24 UHF FF4 SingleAngleRefl - BetterSidelobes Top View [1 large square = 2.5 inches] enlarge 181KB, 1024x741 25 UHF FF4 SingleAngleRefl - BetterSidelobes UHF Raw Gain = 14.2 to 17.3 dBi UHF F/B & F/R Ratio Min. = 15.7 dB enlarge 184KB, 1024x741 26 UHF FF4 SingleAngleRefl - BetterSidelobes UHF SWR (300-ohms) Under 2.3 enlarge 232KB, 1024x741 27 UHF FF4 SingleAngleRefl - BetterSidelobes UHF Impedance enlarge 299KB, 1024x1024 28 UHF FF4 SingleAngleRefl - BetterSidelobes Azimuthal Pattern at 470 MHz enlarge 297KB, 1024x1024 29 UHF FF4 SingleAngleRefl - BetterSidelobes Azimuthal Pattern at 530 MHz enlarge 299KB, 1024x1024 30 UHF FF4 SingleAngleRefl - BetterSidelobes Azimuthal Pattern at 590 MHz enlarge 301KB, 1024x1024 31 UHF FF4 SingleAngleRefl - BetterSidelobes Azimuthal Pattern at 650 MHz enlarge 301KB, 1024x1024 32 UHF FF4 SingleAngleRefl - BetterSidelobes Azimuthal Pattern at 698 MHz enlarge 300KB, 1024x1024 33 UHF FF4 SingleAngleRefl - BetterSidelobes Azimuthal Pattern at 806 MHz enlarge 102KB, 791x1024 34 UHF FF4 SingleAngleRefl - BetterSidelobes 4nec2 File Includes Summary of Dimensions enlarge 28KB, 791x1024 35 UHF FF4 SingleAngleRefl - BetterSidelobes EVAL Summary of Performance enlarge 113KB, 376x1024 36 UHF FF4 SingleAngleRefl - BetterSidelobes Side View [1 large square = 5 inches]
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