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Arts and Crafts
16 - 30 of 671 Total. Shared
Vintage Jools Take 2
16. Vintage Jools Take 2 
10849 Visits
66 Images
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scanjpg1
17. Performing arts center 
5 Visits
0 Images
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kmurphyimages
18. Country drive 4 
6 Visits
0 Images
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kmurphyimages
Antennacraft G-1483 Hoverman Type 2
19. Antennacraft G-1483 Hoverman Type 2  (4 Apr 2013)
Antennacraft G-1483 variation of (SBGH) Hoverman Type 2 (With 4 Reflector Rods) analyzed using 4nec2.

Dimensions per EscapeVelocity, 4nec2 file by <300ohm> as modified by holl_ands: added FR & RP Cards
to facilitate repeatable runs.
14228 Visits
15 Images
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holl_ands
Rocking chair
20. Rocking chair  
10638 Visits
2 Images
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bloodandwhiskeydesign
Army boots
21. Army boots 
11593 Visits
3 Images
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bloodandwhiskeydesign
UHF HD Horizon X10 Two Slot Antenna
22. UHF HD Horizon X10 Two Slot Antenna  (7 Nov 2015)
UHF HD Horizon X10 Two Unequal Slot Antenna from Solid Signal analyzed using 4nec2.  Dimensions derived from a posted
Photo of the Front Panel (compared to Mfr's HxW) and (since a measurement was not available) performance was
calculated for THREE values for Reflector Separation from Front Panel....which is NOT critical for 3.5 to 4.5-inches.
10588 Visits
19 Images
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holl_ands
Bj
23. Bj 
Hope u Will enjoy it <3
12524 Visits
2 Images
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eriksnyder
cm4228hdnoreflHHH
24. cm4228hdnoreflHHH  (20 Oct 2015)
CM4228HD with NO Reflector and HHH (Holl_ands Horizontal Harness) analyzed using 4nec2, SAME version as OPTIMIZED earlier with 16 Reflector Rods.

UHF Raw Gain = 11.7 to 13.8 dBi, F/B & F/R Ratio = 1.7 to 0.5 dB and SWR (300-ohms) = 2.8 (Good).
Hi-VHF Raw Gain = 3.5 to 5.0 dBi, F/B & F/R Ratio = 1.2 to 1.0 dB and SWR (300-ohms) = 3.3 to 4.0 (a bit High).
10236 Visits
21 Images
Linked Album
holl_ands
Hi-VHF Vertical Folded Dipole OMNI
25. Hi-VHF Vertical Folded Dipole OMNI  (29Oct2015)
Hi-VHF Vertical Folded Dipole analyzed using 4nec2.  It provides a TRUE OMNI-Directional Azimuthal Pattern.

Fol. analysis assumed fol. Dimensions:
L2=27.5          ' Folded Dipole Overall Element Length
FW=2.0           ' Distance between Folded Dipole Elements
RACT=0.2845  ' Radius (inches) for Driven Element is Standard Type M 1/2-in O.D. Copper Tubing

Dimensions for other Diameter Tubing can be found in Analysis of Hi-VHF Folded Dipole for Horizontal Polarized signals:
4431 Visits
9 Images
Linked Album
holl_ands
UHF FF3 3-Bay Bowtie - NO Reflector
26. UHF FF3 3-Bay Bowtie - NO Reflector  (21 Oct 2015)
UHF Free-Form 3-Bay (FF3) analyzed using 4nec2 after determining Dimensions using
nikiml's Python Optimization scripts.

Three alternative interconnection Topographies were determined to be of interest for further
investigation (starting with the BEST).  Nearly ALL Bowtie Parameters were allowed to be
INDEPENDENTLY varied in determining the fol. three versions of the FF3 (Free-Form 3-Bay Bowtie):

Note that Gain Charts are for TOTAL (Horiz. + Vert.) Gain.  Azimuthal Charts show that
there is lower, but significant Vertical Gain to the SIDES of the Antenna.

a) Remove Top Bowtie from FF4 (so Offset Feedpoint) and Re-Optimize:

UHF Raw Gain = 8.6 to 11.4 dBi and SWR (300-ohms) Under 2.7 is Good.
Hi-VHF Raw Gain = 2.4 to 3.0 dBi and SWR (300-ohms) = 3.9 to 6.3 is Higher than Desired.

b) Move Feedpoint to Inner Bowtie with Crossover Feedlines to each Outer Bowtie, which
are presumably needed to ensure all three signals are In-Phase at the Feedpoint:

UHF Raw Gain = 8.1 to 10.1 dBi and SWR (300-ohms) Under 2.6 is Good.
Hi-VHF Raw Gain = 2.6 to 2.9 dBi and SWR (300-ohms) = 9.4 to 2.1 is Excessive on Ch7-11.

c) Offset Feedpoint (like a), but with Straight (NO Crossover) Feedlines to each Outer Bowtie:

UHF Raw Gain = 7.1 to 9.4 to 9.1 to 10.7 dBi and SWR (300-ohms) Under 3.1 is a Bit Higher then Desired.
Hi-VHF Raw Gain = 2.1 to 2.6 dBi and SWR (300-ohms) = 7.8 to 6.4
is Excessive.
1607 Visits
87 Images
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holl_ands
UHF M3 3-Bay Bowtie - NO Reflector
27. UHF M3 3-Bay Bowtie - NO Reflector  (20 Oct 2013)
UHF 3-Bay Bowtie [aka M3 (9.5x9.0)] with NO Reflector analyzed using 4nec2.
Height=21-inches, Width=20-inches.

One Bowtie on the M4 (9.5x9.0) 4-Bay Bowtie Antenna was removed to determine the performance of a SHORTER 3-Bay version.
The TOP rather than the BOTTOM Bowtie was removed since it results in a slightly UPWARD tilt (5-10 deg) in the Elevation Pattern in UHF Band.

Raw Gain in the Hi-VHF Band on all but the lowest channels was severely affected as the Gain Pattern shifted to the OVERHEAD direction.
3799 Visits
39 Images
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holl_ands
UHF Multi-Bay Comparison Charts
28. UHF Multi-Bay Comparison Charts  (17 Aug 2009)
Old (Ch14-69) UHF Band is from 470-806 MHz.  New UHF Band is 470-698 MHz.

NOTE: Due to complexity limits in 4nec2 modeling program, most FF4 Reflector models were forced to use
sparse Grid Size (e.g. 4"Hx4"W).  If normal 1"Hx2"W Grid Size is used, F/B and F/R Ratios are significantly improved.

A. Vertically Stacked Comparisons of 2xFF4, 2xM4, 2xCM4221, 2x91XG vs FF6 and two Parabolics:
i) CM4251 and ii) 8-El LPDA with 1-m Refl. & 4ea 1x1-m Refl.

B. FF4, 91XG and Wider Bowtie Modified 91XT Performance Curves for Comparison purposes (not yet
integrated into a single Chart).

C. Multi-Bay Comparisons, presuming NO REFLECTORS and Flat Bowties:

C1. EV's SuperQuad (9.75x9.5) 4-Bay optimized for more Gain on low-mid UHF channels.
C2. mclapp's M4 (9.5x9.0) Super-4-Bay is not only optimized for New UHF Band, but also has low SWR
throughout Hi-VHF Ch7-13.
C3. mclapp's (9.5x9.0x8.5) per his posted 4nec2 file has improved Gain on Ch52-69, but increasing SWR
on Hi-VHF Ch7-9 degrades Net Gain.
C4. Channel Master CM4221 (8.5x8.9), per Actual measurements, is a good performer
on Old and New UHF Bands, but Hi-VHF SWR is somewhat degraded on Ch7-9.
C5. Channel Master CM4221 (7.8x8.0), per Ken Nist's measurements in CM4221a.ez EZNEC file is also a good performer
on Old and New UHF Bands, but SWR and Net Gain are severely degraded on lowest UHF and all Hi-VHF channels.
C6. UTube 4-Bay (from Babblin5 or MakeTV) is a very low performer on both UHF and Hi-VHF Bands, due to insufficient
Bowtie-to-Bowtie separation (5.75-in vs 9.0-in).
C7. Compare Bowties: FF6 (Free-Form 6-Bay) vs FF4 (Free-Form 4-Bay), M4 (9.5x9),
CM4221 (8.5x8.9), CM4221HD (7.9x9.8) and DB-4 (TOO SMALL 6.2x7.9).

D. Multi-Bay Comparisons, presuming Screen REFLECTORS and FLAT Bowties
(Angle along centerline for SuperQuad, Outer 10-inches Angled Forward for M4 and Flat for CM4221) and Flat Bowties:

D1. EV's SuperQuad (9.75x9.5) 4-Bay optimized for more Gain on higher UHF channels.
D2. mclapp's M4 (9.5x9.0) Super-4-Bay is not only optimized for New UHF Band, but also 7.0-3.0 dBi Net Gain
across the Hi-VHF Band, with lowest SWR on Ch7.
D3. Channel Master CM4221 (8.5x8.9), per Actual measurements is a good performer on Old and especially New UHF Bands,
but Hi-VHF SWR and Net Gain are seriously degraded, esp on Ch7-9.  Hi-VHF Gain is 3.5 to 6.5 dB HIGHER
towards the REAR than the FRONT.
D4. Channel Master CM4221 (7.8x8.0), per Ken Nist's measurements in CM4221a.ez EZNEC file is a good performer
on Old and New UHF Bands, but SWR and Net Gain are severely degraded on lowest UHF and all Hi-VHF channels.

E. Multi-Bay Comparisons, presuming Screen REFLECTORS and SWEPT Bowties
(Angle along centerline for SuperQuad, Outer 10-inches Angled Forward for M4 and Flat for CM4221) and Flat Bowties:

E1. EV's SuperQuad (9.75x9.5) 4-Bay optimized for more Gain on higher UHF channels.
E2. mclapp's M4 (9.5x9.0) Super-4-Bay is also optimized for New UHF Band with more gain on lower UHF channels.
Both antennas suffered from excessive SWR in the Hi-VHF Band.

F. Combiner Mod for Old CM4228 compared to original crossover between the two 4-Bay stacks.  Also compared to various
4-Bay antennas.  Above Ch51: Significant improvement. Lowest UHF channels: 3 dB improvement in Raw Gain but only
minor improvement in Net Gain due to poor SWR.

G. New CM4228HD (As Shipped) was much better than old CM4228 on the (problematic) lowest channels,
but had 1-2 dB lower Gain above Ch30.
New CM4228HD was actually somewhat worst than mclapp M4 Super-4-Bay, esp on lowest channels.

H. Combiner Mod for New CM4228HD compared to "As Shipped" to illustrate how much is lost in the horizontal interconnect.
If a low loss RF Combiner Module is used (not an easy task), more than 2 dB of improvement MIGHT be possible...
CM4228HD with Hollands Horizontal Harness (HHH) Mod, essentially MATCHES the RF Combiner Mod UHF Band improvements.

I. Compared fol. 2-Bays+11RR: Triangles, H2 Bowties, Quad-Traps, Bi-Quads, Twin-Loops and Hourglass-Loops.

J. Compared fol. 2-Bay Bowties w/o Reflector: mclapp M2 (9.5x9.0), M2 (10.0x9.5) and the OPTIMIZED H2 (12x11),
with significantly better UHF and Hi-VHF performance.
41043 Visits
59 Images
Linked Album
holl_ands
2m Stick Vertical Dipole
29. 2m Stick Vertical Dipole  (8 Oct 2015)
2-meter Stick Vertical Dipole analyzed using 4nec2.

Raw Gain = 2.05 to 2.13 to 2.22 dBi and SWR (300-ohms) Under 1.44 at 145 MHz
and Under 2.0 from 141 to 150 MHz.

Vertically Polarized Antenna with True OMNI-Directional Response and
minimal Response to Horizontally Polarized signals.

True OMNI, RHCP (Right Hand Circular Polarization) = LHCP (Left Hand Circular
Polarization), so no suppression of Multipath Reflections.
2609 Visits
18 Images
Linked Album
holl_ands
30. 2m Lindenblad Parasitic + Vert. Dipole  (7 Oct 2015)
2-meter (145 MHz) Lindenblad Parasitic Array with Vertical Dipole Active Element analyzed using 4nec2.

Based on lindnbld.ez (EZNEC) File downloaded from http://nec-archives.pa3kj.com/EZNEC_FILES,
which was Imported into 4nec2 and then converted into a Variable SYmbol driven File to facilitate
further analysis, as shown below with Vertical Dipole added.

Vertical Dipole and Parasitic Diagonal Element Lengths were adjusted for minimum SWR (50-ohms)
and minimum LHCP on 145 MHz, assuming Diagonals at 45-deg Angles and separated 1/4-wavelength
away from the Center of the Antenna.  All Elements are AWG12 Copper Wire.

For signals with RHCP (Right Hand Circular Polarization), the Azimuthal Patter is very OMNI.
However, for signals with mostly Horizontal Polarization, there is significantly lower Gain.

When signals are reflected, they usually undergo a change from RHCP to LHCP.  This version of the
Lindenblad Omni Array provides a moderate amount of suppression of these Multipath Reflections.

Parasitic Elements significantly improve Raw Gain Max = 2.9 dBi at 145 MHz and
the Length of the Vertical Dipole has also been adjusted for SWR Min at 145 MHz,
while also adjusting Lengths of Diagonal Parasitic Elements for LHCP Min at 145 MHz.

Note that response to primarily Horizontally Polarized signals is significantly reduced.
0 Visits
0 Images
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holl_ands
 
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