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UHF H2 2-Bay Bowties + Various Refl Rods (4 Mar 2015)UHF H2 (10.5"x12.25") 2-Bay Bowtie with 11 Reflector Rods analyzed using 4nec2 after determining
dimensions using nikiml's Python Optimization Scripts.
UHF Raw Gain = 11.7 to 13.8 dBi, F/B & F/R Ratio Min. = 18.8 dB and SWR (300-ohms) Under 2.6.
Hi-VHF Raw Gain = 7.9 to 7.8 to 7.9 dBi, F/B & F/R Ratio = 9.8 to 15.6 dB and SWR (300-ohms) = 75 to 24.
OPTIMIZED DIMENSIONS:
BowLength = 10.5-in = Whisker Length,
BowSpacing = 12.25-in = Separation between Bowties,
TineSep = 6.0-in = Tine Separation Tip-to-Tip,
FeedSep = 2.5-in = Feedline Separation,
Element & Feedline Wire Size = AWG10,
Reflector Rod Wire Size = QICT (Quarter-Inch Copper Tubing) [Could be thinner],
RS = 5.0-in = Reflector Rod Separation behind Hourglass,
RR = 2.25-in = Reflector Rod-to-Rod Separation,
YRod = 17.0-in = Reflector Rod Half-Lengths. |
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 | 2.
UHF H2 2-Bay Bowties + Screen Reflector (9 Feb 2015)UHF H2 2-Bay Bowtie with Screen Grid Reflector Analyzed using 4nec2 after determining OPTIMUM Dimensions
using nikiml's Python Optimization Scrips. Performance is significantly better than ANY other 2-Bay Bowtie.
Two versions are Optimized and Analyzed....the second clearly outperforming the first:
a) H2 (9.5"x12") 2-Bay Bowtie with 24"Hx24"W Screen Reflector (Grid=2"Hx4"W),
with Hi-VHF Gain to REAR on lower Channels:
UHF Raw Gain = 10.3 to 13.6 dBi, F/B & F/R Ratio Min. = 15.4 dB and SWR (300-ohms) under 2.3.
Hi-VHF Raw Gain = -2 to 8 dBi FORWARD and to REAR Raw Gain = 6.9 to 7.3 to 2.5 dBi with
Hi-VHF F/B & F/R = 10 to -5 dB and SWR (300-ohms) = 125 to 60.8.
Dimensions (inches):
BowLen = 9.5 = Bowtie Whisker Half-Length,
ZBowII = 12.0 = Distance between the Centers of the two Bowties,
TineSep = 8.25 = Bowtie Tine Separation,
BowSwp=0.0 = Bowtie Forward Sweep,
FedSep = 1.75 = Separation (in inches) between two FEEDLINE wires,
RS = -4.75 = Separation between Bowties and Reflector.
Screen Reflector = 24-in H x 24-in W, 2"Hx4"W Grid (1"Hx2"W would improve F/B & F/R Ratios).
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b) H2 (10"x15") 2-Bay Bowtie with 36"Hx36"W Screen Reflector (Grid=1"Hx2"W), with significantly
higher UHF Gain and more Hi-VHF Gain aligned FORWARD:
UHF Raw Gain = 12.9 to 14.5 dBi, F/B & F/R Ratio Min = 22.5 dB and SWR (300-ohms) Under 2.8.
Hi-VHF Raw Gain = 8.2 to 8.6 dBi, F/B & F/R Ratio = 9.8 to 15.9 dB and SWR (300-ohms) = 93 to 31 is Excessive.
Dimensions: (inches)
BowLen = 10.0 = Bowtie Whisker Half-Length,
ZBowII = 15.0 = Distance between the Centers of the two Bowties,
TineSep = 10.0 = Bowtie Tine Separation,
BowSwp=0.0 = Bowtie Forward Sweep,
FedSep = 2.75 = Separation (in inches) between two FEEDLINE wires,
RS = -5.0 = Separation between Bowties and Reflector.
Screen Reflector = 36-in H x 36-in W, 1"Hx2"W Grid. |
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M2 (9.5"x9.0") 2-Bay w Var. Reflectors (31Jan2011)Super-Sized M2 (9.5"x9.0") 2-Bay Bowtie antennas with various alternative reflectors analyzed using 4nec2.
Reflector Separation for all simulations is 4.5", measured from centerline of Bowties.
No SWR reoptimization (e.g. readjust Feedline Separation) has been performed, so there may be room for minor improvements.
The single Vertical or Horizontal BBQ Grates were TOO SMALL, giving away several dB of Gain, but might still be useful.
A pair of BBQ Grates (22"x24") provided slightly MORE gain than a Screen Reflector (2"x4" Grid), although SWR increased a bit.
An 18-in diameter "Pizza Pan" Reflector fell in-between the one and two BBQ Grate alternatives.
Note that a somewhat larger 2-Bay would have improved Raw Gain and SWR performance on the lower frequencies
with minor or no impact on higher frequencies.
Screen reflector (24"x24") using 2"H x 4"W grid was compared to various alternatives based on one or two
11"x25" BBQ Grates (Lowes #201757):
a) M2 (9.5"x9.0") 2-Bay, 24"x24" Grid Reflector: UHF Raw Gain = 9.9 to 13.2 dBi with SWR under 2.4.
Hi-VHF (Ch7-13) Raw Gain = 6.9 to 3.1 dBi but SWR is EXCESSIVE.
b) M2 (9.5"x9.0") 2-Bay, One Vert. Polarized 11"x25" BBQ Grate: UHF Raw Gain = 6.8 to 9.8 dBi with SWR under 2.7 thru Ch51.
c) M2 (9.5"x9.0") 2-Bay, Two Vert. Polarized 11"x25" BBQ Grates: UHF Raw Gain = 7.3 to 9.3 dBi with SWR under 2.3 thru Ch51.
d) M2 (9.5"x9.0") 2-Bay, One Horiz. Polarized 11"x25" BBQ Grate: UHF Raw Gain = 8.7 to 11.3 dBi with SWR under 3.0.
e) M2 (9.5"x9.0") 2-Bay, Two Horiz. Polarized 11"x25" BBQ Grates: UHF Raw Gain = 10.6 to 13.3 dBi with SWR under 3.0.
f) M2 (9.5"x9.0") 2-Bay, Two BENT Horiz. Polarized 11"x25" BBQ Grates: UHF Raw Gain = 10.6 to 13.3 dBi with SWR under 3.1.
Hi-VHF (Ch7-13) Raw Gain = 3.7 to 4.5 dBi but SWR is EXCESSIVE.
g) M2 (9.5"x9.0") 2-Bay, 18" Pizza Pan Reflector: UHF Raw Gain = 8.9 to 9.4 dBi with SWR under 2.5. |
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A-D DB-2 with Reflector (30 Jan 2012)Antennas Direct (OLD) DB-2 with Reflector analyzed using EZNEC file posted by Ken Nist,
as modified to run with 4nec2. Eagle-Aspen 2-Bay appears to have same/similar Dimensions:
http://www.hdtvprimer.com/SIMS/ [Note: Nist's long Twinlead was deleted.]
AWG6 BowLength = 6.3-in, Bowtie Spacing = 7.8-in, Tine Separation = 4.0-in. AWG12 Feedline Separation = 1.7-in.
Angled Screen Reflector 12.8"H x 19.1"W, with outer 1-in bent forward and is 4.0-in from center of Bowties (Grid = 1"H x 2.55"W).
UHF Raw Gain = 2.8 dBi on Ch14, 8-11.5 dBi on higher channels. UHF SWR is under 2.5
Whiskers (Length=6.25-in) are TOO SHORT, resulting in a sharp Raw Gain drop off on Ch14.
Hi-VHF Raw Gain is higher towards the REVERSE (4-6.8 dBi) and up to -4 dBi (Negative Gain) FORWARD. Hi-VHF SWR is EXCESSIVE. |
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