• 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 651 Total. Shared
UHF 7-El FLAT LPDA - OPT
16. UHF 7-El FLAT LPDA - OPT  (14 Jun 2015)
UHF 7-Element FLAT LPDA (Log Periodic Dipole Array) analyzed using 4nec2 after Optimization using nikiml's Python Scripts.

In an LPDA, the Rear Element Length is about a half-wavelenght long at the lowest Frequency (e.g. 470 MHz).
Separation between the REAR Element and the NEXT FORWARD is determined by SIGMA = Dij/2*Lj,
which directly determines the overall LPDA Length.  The "Best" SIGMA is searched for using nikiml's Optimizer.

In the first (Classic LPDA) Analysis below, Each subsequent Element Length is shorter than the
preceding by the factor TAU and each subsequent Element Spacing is shorter than the preceding,
also by the factor TAU = Li/Li+1 = Dij/Djk.  Boom Width = Element Width is determined using nikiml's Optimizer.

In the second Analysis, the Spacings between Elements is still reduced by the factor TAU,
but the Elements Lengths as well as Element & Boom Widths are INDEPENDENT Variables.

======================================
a) Element Width = Boom Width = 1.5 in:

UHF Raw Gain = 7.5 to 8.7 to 8.4 dBi, F/B & F/R Ratio Min = 17.8 dB and SWR (75-ohms) Under 1.6.

======================================
b) Independently Variable Element Widths, Lengths & Boom Width:

UHF Raw Gain = 7.7 to 8.6 dBi, F/B & F/R Ratio Min = 24.5 dB and SWR (75-ohms) Under 1.5.
96 Visits
30 Images
Linked Album
holl_ands
UHF CM4248 15El FD-Yagi + Corner Refl's
17. UHF CM4248 15El FD-Yagi + Corner Refl's  (13 Jun 2015)
UHF CM4248 15-Element Folded Dipole (FD) Yagi with 14 Reflector Rod (RR) Corner Reflector analyzed
using 4nec2 from a file posted by user <300ohm>, which was based on Measurements by Ken Nist,
posted in an EZNEC file on http://www.hdtvprimer.com/ANTENNAS/comparing.html.

Several Modifications to the Corner Reflector were then analyzed, including adding 12 Reflector Rods
half-way between the existing 14 RRs compared to a pair of Screen Reflectors with the same as well as
larger widths.

Three versions are shown here:

======================================
a) CM4248 15El FD-Yagi (Original) with 14 Reflector Rods in Corner Reflector:

UHF Raw Gain = 12.2 to 14.5 dBi, F/B & F/R Ratio = 18 dB and SWR (300-ohms) Under 2.6.

======================================
b) CM4248 15El FD-Yagi - Plus 12 RR's Half-Way Between 14 RR's in Corner Reflector:

UHF Raw Gain = 12.5 to 15.0 dBi, F/B & F/R Min = 22 dB and SWR (300-ohms) Under 2.9.

=====================================
c) CM4248 15El FD-Yagi - Plus Corner Reflector using a Pair of 23x33-in Screen Reflectors (1x1-in Grid):

UHF Raw Gain = 12.2 to 15.0 dBi, F/B & F/R Ratio Min = 20.0 dB and SWR (300-ohms) Under 2.8.

=====================================
All THREE versions are plotted in the Chart, showing only a MINOR (under 0.5 dB) improvement.
The second and third alternatives are essentially the SAME above 518 MHz, but the Reflector Screen
version has less Gain on lower Frequencies.  Wider variations for each version did NOT provide any improvement.
172 Visits
28 Images
Linked Album
holl_ands
Ch14-17 18El FD-Yagi + 20RR Corner - OPT
18. Ch14-17 18El FD-Yagi + 20RR Corner - OPT  (7 Oct 2013)
Ch14-17 18-Element Folded Dipole Yagi with Corner Reflector (20 Reflector Rods) analyzed using 4nec2.
Dimensions (see 4nec2 File) determined using nikiml's Python Optimization Scripts.
Two alternaive Geometries were investigated: the Conventional Corner Angle
Reflector and a Free Form Search for the "Best" arrangement of RANDOMLY placed Reflector
Rods, subject to just a few placement Constraints.
Boom Length = 112-in was intentionally constrained by an non-linear exponential term
in the Python Optimization Script's Target Function.

On Ch14 Raw Gain = 18.6 dBi, F/B & F/R Ratio = 29.9 dB and SWR (300-ohms) under 1.1.

######################################
a) FREE FORM PLACEMENT OF REFLECTOR ROD PAIRS:
Dimensions determined using nikiml's Python Optimization Scripts, using RANDOM placements
of Reflector Rod (RR) PAIRS (symmetric about the Boom) where Optimizer randomly selects
Y-Coordinate Length (12 to 50-in) and X-Z Coordinates within fol. CONSTRAINTS:
i) 18-El Yagi no Longer than about 110-in,
ii) 4 RR Pair between X = -10 and 20-in and Z = +/- 36-in,
iii) 3 RR Pair between X = -10 and 40-in and Z = +/- 40-in,
iv) 3 RR Pair between X = -10 and 150-in and Z = +/- 40-in.

Final DOUBLE-ANGLE configuration is shown below, with five RR pairs in nearly Vertical Row
behind the Yagi's Reflector, one RR Pair in close proximity above/below the Active Folded Dipole,
with the remaining one SHORT RR pair and 3 LONG RR pairs further forward, on a rough approximation
to a Double-Angle Reflector, although proximity to Max-Z may be limiting their ultimate configuration.

UHF Raw Gain = 18.0 dBi on Ch14-17 is LESS than Corner Reflector above.
[Adjusting Optimization Parameters can probably improve on this Preliminary FIRST RUN.]

######################################
b) PARABOLA PLUS ADDITIONAL RR REFLECTOR:
Prior to forming final configuration above, there was a preliminary configuration
with five RR pairs forming a Parabolic shape in close vicinity of Yagi's Rear Reflector,
which is also shown below.  UHF Raw Gain was only somewhat lower: 17.9 dBi.

CORRECTION (22 Nov 2013): Images were ALL replaced by 20 RR (vice incorrect 14 RR) version.

ADDENDUM (22 Nov 2013): First, preliminary run for RANDOM placement of Reflector Rods
was uploaded.  Additional runs need to be conducted to see if Gain can come closer to Corner version.
2060 Visits
30 Images
Linked Album
holl_ands
19. Sunrise Hwy - Mid 
36 Visits
0 Images
Linked Album
kmurphyimages
Hi-VHF 8-El FD-YAGI - OPTimized
20. Hi-VHF 8-El FD-YAGI - OPTimized  (17 May 2015)
Hi-VHF 8-Element Folded Dipole Yagi analyzed using 4nec2 after determining "best" Dimensions
using nikiml's Python Optimization Scripts.

Hi-VHF Raw Gain = 8.9 to 11.4 to 10.2 dBi, F/B & F/R Ratio Min = 19.7 dB and SWR (300-ohms) Under 2.1
206 Visits
12 Images
Linked Album
holl_ands
Hi-VHF 10-El FD-YAGI - OPTimized
21. Hi-VHF 10-El FD-YAGI - OPTimized  (17 May 2015)
Hi-VHF 10-Element Folded Dipole Yagi analyzed using 4nec2 after determining "best" Dimensions
using nikiml's Python Optimization Scripts.
119 Visits
12 Images
Linked Album
holl_ands
22. uhf10elfdyagiopt  (17 May 2015)
UHF 10-Element Folded Dipole Yagi analyzed using 4nec2 after determining "best" Dimensions using nikiml's Python Optimization Scripts.
0 Visits
0 Images
Linked Album
holl_ands
Castaways 2015
23. Castaways 2015  (10 May 2015)
Now in its eighth year, the Castaways Sculpture Awards held on the Rockingham Foreshore, continues to convey the message of recycling to the public, through the use of these creative artworks.
289 Visits
56 Images
Linked Album
gladysclancy
UHF 13-El Twin-Boom LPDA - OPT
24. UHF 13-El Twin-Boom LPDA - OPT  (13 May 2015)
UHF 13-Element Twin-Boom (Layered) LPDA (Log Periodic Dipole Array) with Dimensions Optimized
for Highest Gain (i.e. Sigma = 0.18) using nikiml's Python Scripts.
Boom-Length = 36.7-inches.

UHF Raw Gain = 10.6 to 11.0 to 10.2 to 10.6 dBi, F/B & F/R Ratio Min = 25.0 dB and SWR (75-ohms) under 1.6.

Note that Max UHF Raw Gain occurs when Sigma = 0.213 (per Optimization) and 0.22 (per Parameter Study),
but Quasi-Optimum Sigma = 0.18 is nearly SAME Performance, with much shorter Length, as analyzed here.

.
107 Visits
22 Images
Linked Album
holl_ands
Ch45-51 12-El FD-Yagi - OPTimized
25. Ch45-51 12-El FD-Yagi - OPTimized  (11 May 2015)
Ch45-51 12-Element Folded Dipole Yagi with Optimized Dimensions using nikiml's Python Scripts.  BoomLength = 48.3-in.
148 Visits
15 Images
Linked Album
holl_ands
Hi-VHF 22-El FD-Yagi - OPTimized
26. Hi-VHF 22-El FD-Yagi - OPTimized  (10 May 2015)
Hi-VHF 22-Element Folded Dipole Yagi with Optimized Dimensions determined using nikiml's Python Scripts.
Boom-Length = 217-in (about 18-ft).

Hi-VHF Raw Gain = 12.5 to 15.2 to 13.9 dBi, F/B & F/R Min = 24.0 dB and SWR (300-ohms) Under 2.2.
171 Visits
12 Images
Linked Album
holl_ands
Jewelry Organizer-Holder
27. Jewelry Organizer-Holder  (May 3, 2015)
213 Visits
34 Images
Linked Album
wildrainsphynx
Support the Troops
28. Support the Troops 
137 Visits
5 Images
Linked Album
fulks19
UHF 7-El Wedge & Layered LPDA
29. UHF 7-El Wedge & Layered LPDA  (27 Apr 2015)
UHF 7-Element Layered LPDA (Log Periodic Dipole Array with Top and Bottom Arrays parallel to each other)
was found after trying to Optimize the Wedge version (with Inclusive Angle = 2* HalfAngle) and finding that
it was essentially a Layered version...which was then partially Re-Optimized to find the "best" Separation
between the Top and Bottom set of LPDA Elements.  Python Optimization Scripts from nikiml were used
to find the "best" set of dimensions.

Two versions are analyzed here: a) 7-El Wedge LPDA and b) 7-El Layered LPDA, with ALL SAME Dimensions,
except for Separation between Top & Bottom sets of LPDA Elements.

a) 7-El Wedge LPDA:

UHF Raw Gain = 7.9 to 9.0 to 8.1 dBi, F/B & F/R Ratio Min = 22.5 dB and SWR (75-ohms) Under 1.8.

===============================================================
b) 7-El Layered LPDA:

UHF Raw Gain = 7.9 to 9.0 to 7.9 dBi, F/B & F/R Ratio Min = 21.0 dB and SWR (75-ohms) Under 1.9.
[NOTE: More accurate EVAL found only 0.1 dBi less Gain at 698 MHz, see EVAL RESULTS Files.]
.
171 Visits
37 Images
Linked Album
holl_ands
The Beat
30. The Beat 
138 Visits
132 Images
Linked Album
hpdramaclub
 
 Prev 15 | Next 15