• Public Gallery  • Help  
• Join Now!  • Log In  • Feature Tour
Select Category
Animals and Pets Arts and Crafts Cars and Transportation Events
Family Friends For Sale Holidays
Miscellaneous Nature and Landscapes Photography Schools and Organizations
Sports and Hobbies Travel and Vacation Weddings Most Recent
Search Public Gallery Albums: (keywords or username)
 Public Gallery | Home > Arts and Crafts Prev 15 | Next 15 
Arts and Crafts
16 - 30 of 577 Total. Shared
UHF Fractal Bowtie - No Reflector
16. UHF Fractal Bowtie - No Reflector  (21 Jan 2013)
UHF 4th Order Sierpinski Arrowhead (Fractal) Bowtie analyzed using 4nec2.

Three feedpoint geometries were analyzed:
1) End-Fed Anti-Symmetric (mirrored on Centerpoint vice Z-Axis) provided best Raw Gain and SWR,
but SWR was excessive on the lower frequencies, limiting the useful bandwidth.
The sharp dive in the (Forward) Gain curve corresponds to when the Azimuthal Pattern changes into a four-leaf clover,
with minimal Forward Gain...also note that Real Part of Impedance, R(ohm), nose dives down to only 25-ohms,
resulting in a very high SWR peak.  These severely limit the usable bandwidth.

2) End-Fed Symmetric (mirrored on Z-Axis) had poor Raw Gain and SWR identical to End-Fed Anti-Symetric.

3) Center-Fed Symmetric had poor Raw Gain as well as poor SWR.

These antennas would need to be Rescaled to match the desired operating band since they were very poor matches
for existing UHF Band.  SOURCE Wire length should them be varied to obtain best SWR.
900 Visits
18 Images
Linked Album
holl_ands
UHF Bowties - NO Reflector
17. UHF Bowties - NO Reflector  (20 Apr 2010)
Five UHF Bowtie variations (with NO Reflectors) analyzed using 4nec2.  ALL except Solid Triangle are AWG10.

Solid Triangle Bowtie:         UHF Raw Gain = 3.4 - 6.3 dBi and SWR (300-ohms) under 2.6 [EXCL].
Six-Whisker Tricon Bowtie: UHF Raw Gain = 3.1 - 5.1 dBi and SWR (300-ohms) under 2.0 [EXCL].
Six-Whisker Bowtie:           UHF Raw Gain = 3.4 - 5.0 dBi and SWR (300-ohms) under 2.4 [EXCL].
Four-Whisker Bowtie:         UHF Raw Gain = 3.2 - 5.3 dBi and SWR (300-ohms) under 3.0 [FAIR].
Enclosed Bowtie:               UHF Raw Gain = 3.8 - 5.4 dBi and SWR (300-ohms) under 3.3 [FAIR].
Indented Bowtie:               UHF Raw Gain = 3.6 - 5.5 dBi and SWR (300-ohms) under 4.2 [POOR].

Highest Raw Gain was provided by optimized Solid Triangle, about 1 dB higher on highest freqs.
Flattest Gain was (tie) 6-Whisker & Enclosed Bowtie, latter had Highest Gain on Low Channels.

Optimum dimensions determined by nikiml's Optimization Scripts were Hypotenuse=9.75-in,
Tip-to-Tip Vertical Separation=12-in and Feedline Separation=1.0-in.  Hi-VHF analysis is also provided.

Six-Whisker had better SWR (300-ohms) than Four-Whisker version.
Tine Separation is measured between upper and lower Whisker Tips.
Quasi-optimum 6-Whisker sizes for ALL AWG10 wire sizes:
All BowLength=10-in, TineSeparation=5-in and Feedline Separation=1.5in.
Total WIDTH is 21.5-in, which is a ONE-Wavelength at 549 MHz (middle of the band).
Contrast this to a Dipole which has minimum SWR of about 75-ohms closer to a HALF-Wavelength.

All models had AGT=1.0 (no Gain correction) with No Warnings or Errors, except for 6-Whisker Bowtie:
4nec2's Automatic Gain Test (AGT) would not go below 0.41 dB (UHF) and 0.29 dB (Hi-VHF).
Subtract these corrections from 6-Whisker 4nec2 Gain results below.
The 6-Whisker Tri-Conn Bowtie did NOT require any AGT corrections.

EDIT (7Sep2011): Added 4-Whisker, Enclosed and Indented Bowties.

EDIT (20Jun2013): Added Solid Triangle Bowtie using 33-Wire Model using nikiml's Optimization Scripts.
See CM4251 Parabolic+2-Bay+Grid-Reflector analysis for alternative 265-Wire Model.

EDIT (18Jul2014): Added 6-Whisker Bowtie with Tri-Conn (Triple Connector) between Whiskers and the Balun Feedpoint.  AGT is much easier to adjust.
2319 Visits
69 Images
Linked Album
holl_ands
Hi-VHF+UHF Stick Dipole - No Reflector
18. Hi-VHF+UHF Stick Dipole - No Reflector  (24 Jul 2014)
Hi-VHF+UHF Stick Dipole (NO Reflector) analyzed using 4nec2.

Two versions were analyzed:
a) Optimized for Hi-VHF Band,
b) Jointly Optimized for Hi-VHF & UHF Bands, using nikiml's Optimization Python Scripts.

###############################################
a) Optimized for Hi-VHF Band: Overall Length = 28.2-inches.

Hi-VHF Raw Gain = 1.8 to 2.0 dBi and SWR (75-ohms) Under 2.8.

###############################################
b) Jointly Optimized for Hi-VHF and UHF Bands: Length = 25.6-inches.

Hi-VHF Raw Gain = 2.0 to 2.2 dBi and SWR (75-ohms) Excessive on Lower Channels.

UHF Raw Gain = 4-5 dBi in lower UHF Band and then rolls off above about 580 MHz.
56 Visits
36 Images
Linked Album
holl_ands
Lo+Hi-VHF 1-Bay Bowtie
19. Lo+Hi-VHF 1-Bay Bowtie  (24 Nov 2012)
Lo-HiVHF (Ch2-13) 1-Bay Bowtie analyzed using 4nec2 after optimizing via nikimil's Python scripts.

Provides more Gain than Stick Dipole or Folded Dipole across BOTH Ch2-6 Lo-VHF and Ch7-13 Hi-VHF Bands.
However, narrow beamwidth on Ch7-13 requires careful aiming.

Optimized size is BIG (15.75-ft Wide by 4.25-ft High), using 1/4-in O.D. Copper (may use larger, incl. 3/8-in Aluminum):
Each of Six Whiskers = 92-inches, Top-Bottom Tine Separation = 51-inches & Feedpoint = 5-inches.
966 Visits
12 Images
Linked Album
holl_ands
V-Stack Hi-VHF Circular Loops
20. V-Stack Hi-VHF Circular Loops  (16 Jul 2014)
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 Minimum = 15.1 dB and 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).
RS = 13.0-inches = Separation between Reflectors and Circular Loops
VS = 50-inches = Vertical Separation (Center-to-Center, in inches).

#################################################
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 and 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 interconnects Stacked Antennas:
Hi-VHF Raw Gain = 11.5 to 10.3 dBi, F/B & F/R Min = 16.1 dB and 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).
129 Visits
32 Images
Linked Album
holl_ands
Hi-VHF Goalkeeper Quad-Trapezoid+Spurs
21. Hi-VHF Goalkeeper Quad-Trapezoid+Spurs  (22 Jul 2014)
Hi-VHF Goalkeeper, a Quasi-Omni [accidental] variation of the Quad-Trapezoid+Spurs
was analyzed using 4nec2.

Provides Bi-Directional Pattern firmly aligned along the X-Axis with 100-110 degrees Beamwidth
and NULLs to the sides.  Although Horizontally Polarized, it also provides both
Right-Hand and Left-Hand Circular Polarization.
39 Visits
12 Images
Linked Album
holl_ands
Hi-VHF Goalkeeper Quad-Trapezoid+Spurs
22. Hi-VHF Goalkeeper Quad-Trapezoid+Spurs  (22 Jul 2014)
Hi-VHF Goalkeeper, a Quasi-Omni [accidental] variation of the Quad-Trapezoid+Spurs
was analyzed using 4nec2.

Provides Bi-Directional Pattern firmly aligned along the X-Axis with 100-110 degrees Beamwidth
and NULLs to the sides.  Although Horizontally Polarized, it also provides both
Right-Hand and Left-Hand Circular Polarization.
50 Visits
12 Images
Linked Album
holl_ands
FM - Goalkeeper Quad-Trapezoid+Spurs
23. FM - Goalkeeper Quad-Trapezoid+Spurs  (22 Jul 2014)
FM - Goalkeeper, a Quasi-Omni [accidental] variation of the Quad-Trapezoid+Spurs
was analyzed using 4nec2.

Provides Bi-Directional Pattern firmly aligned along the X-Axis with 100-110 degrees Beamwidth
and NULLs to the sides.  Although Horizontally Polarized, it also provides both
Right-Hand and Left-Hand Circular Polarization.
65 Visits
12 Images
Linked Album
holl_ands
UHF Double Rhomboid
24. UHF Double Rhomboid  (10 Mar 2010)
UHF Double Rhomboid (18.4 ft long by 8.2 ft wide, AWG12) analyzed using 4nec2.
Although the differences were small, "best" value for Termination Resistors was 300-ohms.
1163 Visits
16 Images
Linked Album
holl_ands
UHF 2x2-Bay (H4) with Building Reflector
25. UHF 2x2-Bay (H4) with Building Reflector  (21 Jul 2014)
UHF 2x2-Bay Bowtie (H4) with Building used as a Reflector analyzed using 4nec2.  Separation from side of Building was assumed to be 4.5-inches.
59 Visits
15 Images
Linked Album
holl_ands
Hi-VHF Circular Loop + Reflector
26. Hi-VHF Circular Loop + Reflector  (15 July 2009)
Hi-VHF Circular Loop with either Loop or Screen Reflector analyzed using 4nec2.

a) With Loop Reflector, Net Gain was 8 dBi on Ch7, dropping to 6 dBi on Ch13 with excellent SWR, except for small increase on Ch7.

Adding Loop Reflector increased Net Gain by 2-4 dB (less at high freqs) with more than 8.7 dB F/B (and F/R) using

Optimum Diameter=22-in for Half-Inch Copper Tubing.  Best F/B (and F/R) is on Ch8-10.

Optimum Diameter=21.5-in for Quarter Inch Copper Tubing (QICT) was nearly as good, with more than 7.3 dB F/B (and F/R).
Smaller Circular Loop Element sizes not analyzed since a Square Loop (Quagi) would be easier to construct.

Loop Reflector dimensions are optimized for full Hi-VHF Band coverage.
Rescaling to optimize Ch7 will have only minor-moderate impact to Ch13 F/B, F/R and SWR.
However, rescaling to optimize Ch11-13 will degrade F/B, F/R and especially SWR on CH7-10.

b) EDIT (16 Sep 2009): Added analysis of alternative Hi-VHF Loop with 28x34-in Screen Reflector.

c) EDIT (5 Oct 2013): Added analysis of alternative Hi-VHF Loop with 40x40-in Screen Reflector to improve F/B & F/R Ratios.

d) EDIT (15 Jul 2014): Added Circular Polarization analysis of alternative Hi-VHF Loop with 28x34-in Screen Reflector.
2383 Visits
43 Images
Linked Album
holl_ands
Compare Loops
27. Compare Loops  (16 Jul 2014)
Charts Comparing Loop Performance.
658 Visits
8 Images
Linked Album
holl_ands
UHF Quad-Trapezoid-Loop
28. UHF Quad-Trapezoid-Loop  (11 Jul 2014)
UHF Quad-Trapezoid-Loop Antenna analyzed using 4nec2, formed by adding outer parts
of Chireix 2-Square to an Hourglass-Loop.  All dimensions determined using nikiml's
Optimization Scripts.

Two versions analyzed: Quad-Trap (NO Reflector) and Quad-Trap (15 RR).

=================================================
a) Quad-Trapezoid-Loop (NO Refl):

UHF Raw Gain = 6.7 to 8.4 to 7.8 dBi and SWR (300-ohms) under 1.8.

=================================================
b) Quad-Trapezoid-Loop + 15 Reflector Rods:

UHF Raw Gain = 10.1 to 11.8 dBi, F/B & F/R Ratio Min =19.2 dB and SWR (300-ohms) under 2.7.

Note the VERY WIDE BANDWIDTH, 60-degrees ALL across the UHF Band and the VERY DEEP
49+ dB Notch directly to the Rear.
3305 Visits
30 Images
Linked Album
holl_ands
V-Stack UHF Hourglass-Loop + 15RR
29. V-Stack UHF Hourglass-Loop + 15RR  (11 Jul 2014)
V-Stack UHF Hourglass-Loop + 15RR
UHF Vertically Stacked Hourglass-Loops with 15 Reflector Rods  analyzed using 4nec2
where nikiml's Python Optimization Scripts were used to Optimize dimensions of the
HVH (Hollands Vertical Harness) and  Separation between Hourglass-Loops.
3057 Visits
18 Images
Linked Album
holl_ands
Gabriella Remes Canadian Original Art
30. Gabriella Remes Canadian Original Art   (July 8, 2014)
Hello my Name is Gabriella Remes. I am a Canadian Local Artist and Paint for my Living. Up for Sale are these Painting of Different Scenes. My Favorites items
to Paint are Birds and Flowers. If there is anything you
like email me at gabriellaremes@yahoo.com.
5949 Visits
6 Images
Linked Album
wrestlingfanaticactionfigures
 
 Prev 15 | Next 15 

Share images with friends & family, Send Invitation or Share URL: