Vertically Stacked Hi-VHF Circular Loops analyzed using 4nec2.
Three Versions are presented: a) Lossless RF Combiner Mod emulated by Two Independent Sources b) Two Equal-Length 300-ohm (Twin-lead) Transmission Feedlines c) Hollands Vertical Harness interconnects Stacked Antennas
[In Hi-VHF Band, all Dimensions can be rounded to nearest 1/4-inch.]
################################################# a) Lossless RF Combiner Mod emulated by Two Independent Sources: Hi-VHF Raw Gain = 11.2 to 11.3 dBi, F/B & F/R Ratio Min = 15.1 dB & SWR (300-ohms) under 2.9. ACTUAL RF Combiner Loss will reduce calculated Gain by about 0.5 to 1.0+ dB.
Circular Elements = 1/4-inch Copper Tubing (QICT). VS = 50-inches = Vertical Separation (Center-to-Center, in inches). RS = 13.0-inches = Separation between Reflectors and Circular Loops. [At 14.0-in, SWR is under 2.7 (preferred target) with only 0.1 to 0.2 dB decrease in Gain.]
################################################# b) Two Equal-Length 300-ohm (Twin-lead) Transmission Feedlines: Hi-VHF Raw Gain = 10.1 to 10.3 dBi, F/B & F/R Ratio Min = 18.4 dB & SWR under 2.3. Rain, Snow & Ice will significantly increase Loss in the Twinlead.
Circular Elements = 1/4-inch Copper Tubing (QICT). VF = 0.83 = "Typical" Velocity Factor of 0.83, cheap R-S Twinlead measured low as 0.77. OPTIMIZED DIMENSIONS: RS = 13.5-inches = Separation between Reflectors and Circular Loops VS = 33.87-inches = Vertical Separation (Center-to-Center, in inches). Lx = 20.87-inches = OPTIMIZED Extension to Length (in INCHES) of Transmission Line: Lt = 26.31-inches = Lx-11.5+VS/2 = PHYSICAL Length (in INCHES) of Each Transmission Line Le = 0.8052-meters = Lt/(39.36*VF) = ELECTRICAL Length (in METERS!!!) of Each Transmission Lines
################################################# c) Hollands Vertical Harness (HVH) interconnects Stacked Antennas: Hi-VHF Raw Gain = 11.5 to 10.3 dBi, F/B & F/R Min = 16.1 dB & SWR (300-ohms) under 2.3.
Circular Elements & Harness = 1/4-inch Copper Tubing (QICT). Gap = 0.75-inches = Feedpoint Gap in Circular Loops. VS = 50.0-inches = Vertical Separation (Center-to-Center, in inches). OPTIMIZED DIMENSIONS: RS = 13.75-inches = Separation between Reflectors and Circular Loops Xh = -6.31-inches = Harness X-Axis Separation from Plane of Circular-Loops. Yw = 2.21-inches = Y-Axis Width of Harness Separation. Zh = 17.87-inches = Length of Harness Wires between Balun Feedpoint and Diagonal to Circular Loop. Ld = 7.71-inches = Lengths of Diagonal Harness Wires to Gap in Circular Loops.
Lharn = 52.5-inches = 2*Zh+2*Ld+2*(0.67 for wire loop ends) = Harness Wire Total Lengths (2 required).
Date(s): 16 Jul 2014. Album by holl_ands. 1 - 32 of 32 Total. 2374 Visits.
enlarge 155KB, 643x1024 1 V-Stack Hi-VHF Circular Loops RF Combiner Mod Version 3D View
enlarge 281KB, 639x1024 2 V-Stack Hi-VHF Circular Loops RF Combiner Mod Version Front View [1 large square = 5 inches]
enlarge 100KB, 791x1024 3 V-Stack Hi-VHF Circular Loops RF Combiner Mod Version 4nec2 File
enlarge 175KB, 1024x675 4 V-Stack Hi-VHF Circular Loops RF Combiner Mod Version UHF Raw Gain vs VS at 174 MHz VS = Vertical Stacking Distance (Loop Center-to-Center)
enlarge 168KB, 1024x675 5 V-Stack Hi-VHF Circular Loops RF Combiner Mod Version UHF Raw Gain vs VS at 198 MHz VS = Vertical Stacking Distance (Loop Center-to-Center)
enlarge 179KB, 1024x675 6 V-Stack Hi-VHF Circular Loops RF Combiner Mod Version UHF Raw Gain vs VS at 216 MHz VS = Vertical Stacking Distance (Loop Center-to-Center)
enlarge 179KB, 1024x690 7 V-Stack Hi-VHF Circular Loops RF Combiner Mod Version Hi-VHF Raw Gain = 11.2 to 11.3 dBi Hi-VHF F/B & F/R Ratio Minimum = 15.1 dB
enlarge 192KB, 1024x690 8 V-Stack Hi-VHF Circular Loops RF Combiner Mod Version Hi-VHF SWR (300-ohms) Under 2.9
enlarge 228KB, 1024x690 9 V-Stack Hi-VHF Circular Loops RF Combiner Mod Version Hi-VHF Impedance
enlarge 303KB, 1024x1024 10 V-Stack Hi-VHF Circular Loops RF Combiner Mod Version Azimuthal Pattern at 174 MHz
enlarge 303KB, 1024x1024 11 V-Stack Hi-VHF Circular Loops RF Combiner Mod Version Azimuthal Pattern at 198 MHz
enlarge 307KB, 1024x1024 12 V-Stack Hi-VHF Circular Loops RF Combiner Mod Version Azimuthal Pattern at 216 MHz
enlarge 124KB, 683x1024 13 V-Stack Hi-VHF Circular Loops 2xTL (300-ohm Transmission Line) Version 3D View
enlarge 260KB, 712x1024 14 V-Stack Hi-VHF Circular Loops 2xTL (300-ohm Transmission Line) Version Front View [1 large square = 5 inches]
enlarge 180KB, 1024x690 16 V-Stack Hi-VHF Circular Loops 2xTL (300-ohm Transmission Line) Version Hi-VHF Raw Gain = 10.1 to 10.3 dBi Hi-VHF F/B & F/R Ratio Minimum = 18.4 dB
enlarge 187KB, 1024x690 17 V-Stack Hi-VHF Circular Loops 2xTL (300-ohm Transmission Line) Version Hi-VHF SWR (300-ohms) Under 2.3
