Hi-VHF and UHF Tapered Loop with Screen Grid Reflector PLUS Hi-VHF Stick Dipole analyzed using 4nec2, approximating Dimensions for Antennas-Direct C2-V.
DIMENSIONS Per ADTech and user freezer: Inner Loop Diameter 6-1/4", Outer Loop Diameter 8-5/8" with 1/2" Overlap at Feedpoint. Gen-I/II VHF Dipole = 37-7/8-in, Reflector = 20-1/8" H x 11-5/8" W x 4-1/16" "Deep". Feedpoint DETAILS found towards the bottom of fol. webpage: http://www.hdtvprimer.com/ANTENNAS/TemporaryPage.html
ADTech indicated that there are actually THREE DIFFERENT Generations of the C2-V, using different VHF Impedance Matching Approaches [NOT analyzed in below results]: "First and second generation C2Vs used a standard 300/75 ohm matching transformer to match the dipole to the Holland UVSJ's VHF input. Because of the built-in mismatch, the length of the dipoles was increased to bring the return loss back down in the center of the VHF band. Third generation C2Vs that utilize the VHF-1 module utilize a custom PCB matching network that's closer to a 1:1 ratio, allowing the dipole elements to be shortened by 3.25" inches each while still having the best return loss at mid-band. The VHF-1 module includes the UVSJ function internally."
====================================== Four variations were analyzed: UHF C2 with Reflector, Gen-I/II C2-V adding Hi-VHF Dipole, Gen-III/VHF Module C2-V and C2 without Reflector.
a) C2 Tapered Loop with Screen Grid Reflector:
UHF Raw Gain = 9.6 to 10.1 dBi, F/B & F/R Minimum = 14.9 dB and SWR (300-ohms) Under 1.9. [A-D C2 Specs: Gain = 9.7 to 10.2, F/B = 20 dB (typ), 22 dB (max at 698 MHz) and SWR (300-ohms) under 3.0.]
====================================== b) Gen-I/II C2-V Tapered Loop, Screen Grid Reflector + Hi-VHF Dipole, connected to UVSJ via 300:75-ohm Balun:
UHF Raw Gain = 9.4 to 10.1 dBi, F/B & F/R Ratio Minimum = 17.9 dB and SWR (300-ohms) Under 2.4. Hi-VHF Raw Gain = 2.7 to 3.2 dBi, Hi-VHF F/B & F/R Ratio = 0.3 to 0.6 dB and SWR (300-ohms) Under 2.4.
Note the mid-band UHF Loss of about 0.5 dB when adding the VHF Dipole.
Note that despite the VHF Dipole being slightly SHADED by being mounted BEHIND the Reflector, Hi-VHF Gain was 0.9 to 1.2 dB HIGHER than JUST an Optimized Hi-VHF Dipole [see Link below], with 0.25 to 0.5 dB MORE in the Forward Direction, so the Reflector must have been acting to squeeze out more Gain at the expense of Horizontal and Vertical Beamwidths. Also note that the Side NULLS were limited to about -17 to -15 dBi Gain [A-D calculated -16 to -14 dBi], rather than forming very deep Nulls more typical of a Dipole without other surrounding Metal: https://imageevent.com/holl_ands/dipoles/hivhfuhfstickdipolenoreflector
====================================== c) Gen-III/VHF Module C2-V Tapered Loop, Screen Grid Reflector + Hi-VHF Dipole, combined with UHF Coax via Impedance Matching Network:
====================================== d) C2 Tapered Loop with Reflector REMOVED, so Bi-Directional:
UHF Raw Gain = 5.5 to 6.8 dBi and SWR (300-ohms) Under 3.2.
Note that INCREASE in Raw Gain is quite significant as the Thickness (Relem) becomes as thin as Aluminum Foil...with INCREASE to excessive SWR=4.0 at 470 MHz. Al. Foil Relem(STD)=0.000315-in and Relem(HD)=0.00047-in. However, note that assumed Relem=0.0404 (14-Gauge...or perhaps thinner 16-Gauge) is best match to A-D C2 Specs, esp. SWR. In below Charts [#52-57], Alum. Foil is on Far Left and AWG-16 on Far Right.
====================================== EDIT (2Apr2015): Uploaded revised charts based on refined dimension information from ADTech.
EDIT (4Dec2016): Added charts showing how Raw Gain INCREASES as the Thickness (Relem) is reduced.
Date(s): 18Jan2015. Album by holl_ands. 1 - 57 of 57 Total. 9789 Visits.