Hi-VHF 9-Element Folded Dipole Yagi, including 3 Reflector Rods, MCM Stellar Labs 30-2475, analyzed using 4nec2. Initial Dimensions were provided by user [MikeBear]. Analysis revealed that Antenna per MikeBear's Measurements were very close to OPTIMUM, for the chosen use of Three Reflector Rods....but Repurposing Two RR's as Directors improved Raw Gain on Ch13 by about 1 dB and F/R Ratio improved several dB on Lower Channels.
Several Versions are presented here [For comparison, completely Re-Optimized 9-El FD-Yagi's are Analyzed in another Album]:
a) Per MikeBear Measurements with Upper/Lower Reflector Rods 2-in in FRONT of Middle Reflector Rod:
HiVHF Raw Gain = 8.7 to 10.8 dBi, F/B & F/R Ratio = 10.3 to 21.0 to 19.2 to 19.8 dB [Poor on Low Channels] and SWR (300-ohms) is Under 2.2 (EXCELLENT).
Moving the X and/or Z-Coordinates of the two Upper/Lower Reflector Rods in vicinity of current locations did NOT significantly improve either Gain, SWR or F/R Ratio. Boom Length = 59.375-in + Ends.
==================================== b) Analyzed Upper/Lower Reflector Rods Repurposed as Two Additional Directors: [Requires a Front Boom Extension.]
HiVHF Raw Gain = 8.6 to 12.0 dBi, F/B Ratio = 14.1 dB and SWR (300-ohms) Under 2.2.
Improves Ch13 Gain and F/R Ratio on Lower Channels. SWR is Excellent. New Boom Length = 95.7-in + Ends
c) Upper/Lower Reflector Rods were removed to investigate degradation to F/R Ratio (at expense of Raw Gain). See below Charts for results.
d) ALL three Reflector Rods were removed to investigate degradation to F/R Ratio (at expense of Raw Gain). See below Charts for results.
e) Location of Upper/Lower Reflector Rods relative to Middle Reflector was Re-Optimized, but there was NO overall improvement when Constrained to be BEHIND the Folded Dipole.
==================================== CORRECTION (14 Dec 2015): This 9-El FD Yagi Analysis replaces Earlier Analysis (8-El FD Yagi) that was MISSING Director just 2.5-in in front of Folding Dipole [very hard to see in mfr diagram]. There was only a few tenths of dB change in Performance with much lower SWR.
Date(s): 14 Dec 2015. Album by holl_ands. 1 - 34 of 34 Total. 6616 Visits.
enlarge 245KB, 1152x717 2 HiVHF 9-El FD-Yagi - Stellar Labs 302475 Top View [1 large square = 5 inches]
enlarge 145KB, 1152x429 3 HiVHF 9-El FD-Yagi - Stellar Labs 302475 Side View [1 large square = 5 inches]
enlarge 162KB, 1024x647 4 HiVHF 9-El FD-Yagi - Stellar Labs 302475 HiVHF Raw Gain = 8.7 to 10.8 dBi HiVHF F/B & F/R Ratio = 10.3 to 21.0 to 19.2 to 19.8 dB
enlarge 59KB, 1024x1015 16 HiVHF 9-El FD-Yagi - Stellar Labs 302475 If Repurpose 2 RR's for 2 Directors 3D View
enlarge 170KB, 1152x629 17 HiVHF 9-El FD-Yagi - Stellar Labs 302475 If Repurpose 2 RR's for 2 Directors Top View [1 large square = 12.5 inches]
enlarge 115KB, 1152x428 18 HiVHF 9-El FD-Yagi - Stellar Labs 302475 If Repurpose 2 RR's for 2 Directors Side View [1 large square = 12.5 inches]
enlarge 181KB, 1024x647 19 HiVHF 9-El FD-Yagi - Stellar Labs 302475 If Repurpose 2 RR's for 2 More Directors HiVHF Raw Gain = 8.6 to 12.0 dBi HiVHF F/B Ratio = 14.1 dB
enlarge 200KB, 1024x647 20 HiVHF 9-El FD-Yagi - Stellar Labs 302475 If Repurpose 2 RR's for 2 More Directors HiVHF SWR (300-ohms) Under 2.2
enlarge 232KB, 1024x647 21 HiVHF 9-El FD-Yagi - Stellar Labs 302475 If Repurpose 2 RR's for 2 More Directors HiVHF Impedance
enlarge 316KB, 1024x1024 22 HiVHF 9-El FD-Yagi - Stellar Labs 302475 If Repurpose 2 RR's for 2 More Directors Azimuthal Pattern at 174 MHz
enlarge 318KB, 1024x1024 23 HiVHF 9-El FD-Yagi - Stellar Labs 302475 If Repurpose 2 RR's for 2 More Directors Azimuthal Pattern at 198 MHz
enlarge 317KB, 1024x1024 24 HiVHF 9-El FD-Yagi - Stellar Labs 302475 If Repurpose 2 RR's for 2 More Directors Azimuthal Pattern at 216 MHz
enlarge 316KB, 1024x1024 25 HiVHF 9-El FD-Yagi - Stellar Labs 302475 If Repurpose 2 RR's for 2 More Directors Elevation Pattern at 174 MHz
enlarge 316KB, 1024x1024 26 HiVHF 9-El FD-Yagi - Stellar Labs 302475 If Repurpose 2 RR's for 2 More Directors Elevation Pattern at 198 MHz
enlarge 323KB, 1024x1024 27 HiVHF 9-El FD-Yagi - Stellar Labs 302475 If Repurpose 2 RR's for 2 More Directors Elevation Pattern at 216 MHz
enlarge 30KB, 791x1024 28 HiVHF 9-El FD-Yagi - Stellar Labs 302475 If Repurpose 2 RR's for 2 More Directors 4nec2 File includes Summary of Dimensions
enlarge 26KB, 791x1024 29 HiVHF 9-El FD-Yagi - Stellar Labs 302475 If Repurpose 2 RR's for 2 More Directors EVAL Summary of Performance
enlarge 29KB, 791x1024 30 HiVHF 9-El FD-Yagi - Stellar Labs 302475 If Repurpose 2 RR's for 2 More Directors EVAL *.html Performance Summary File
enlarge 181KB, 1152x688 31 HiVHF 9-El FD-Yagi - Stellar Labs 302475 Front View [1 large square = 5 inches]
enlarge 249KB, 1024x696 32 HiVHF 9-El FD-Yagi - Stellar Labs 302475 Compare Versions: Raw Gain & SWR
enlarge 269KB, 1024x696 33 HiVHF 9-El FD-Yagi - Stellar Labs 302475 Compare Versions: Raw Gain & F/R Ratio
enlarge 123KB, 1152x471 34 HiVHF 9-El FD-Yagi - Stellar Labs 302475 If Repurpose 2 RR's for 2 More Directors Front View [1 large square = 5 inches]
