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UHF CM4221HD (Hacked) - No Reflector
16. UHF CM4221HD (Hacked) - No Reflector  (18 Oct 2013)
UHF CM4221HD (Hacked) and NO Reflector analyzed using 4nec2.

CM4221HD measurements per fol. smpowell55 posts:
http://www.digitalhome.ca/forum/showthread.php?p=863127
http://www.digitalhome.ca/forum/showthread.php?p=863559

UHF Raw Gain = 7.4 to 12.2 dBi and SWR (300-ohms) under 2.6.
Hi-VHF Raw Gain = 4.1 to 4.2 dBi and SWR (300-ohms) = 17 to 1.1.
SWR on Ch7-10 degrades Net Gain & EVM (Error Vector Magnitude), but may be adequate for strong stations.
NOTE: As-shipped PCB Balun KILLS VHF.  Above Hi-VHF performance presumes replace with
conventional Transformer (Cylindrical) Balun.

BowLength = 7.9-in, Inner-Inner Bowtie Spacing = 9.84-in, Outer-Inner Bowtie Spacing = 8.46-in,
Tine Separation = 3.94-in.  Feedline Separation = 1.18-in, with 0.8-in at Crossover (2" from Outer Bowtie).
16 Rod Reflectors: 23.6" Long with 1.93" Spacings for Total Height = 30-in.  Separation from Bowties = 4.25-in.

It is presumed that anyone interested enough to view this webpage will
implement the "Hacked Balun" modifications per photo in fol. rabbit73 post
(flip over the Feedlines going into the Balun plus an additional offset):
http://www.digitalhome.ca/forum/showthread.php?p=1167870
1419 Visits
21 Images
Linked Album
holl_ands
UHF 21El Curtain Array - NO Refl
17. UHF 21El Curtain Array - NO Refl  (20 Oct 2014)
UHF 21-Element Curtain Array (NO Reflector) analyzed using 4nec2 after RESCALING Wi-Fi version posted by Ross Anderson, W1HBQ.  Also corrected AGT=1.0 after fixing SOURCE Wire Statement error.
572 Visits
13 Images
Linked Album
holl_ands
horizstackff4dblanglerefl+HHH
18. horizstackff4dblanglerefl+HHH  (17 Oct 2014)
Horiz-Stack FF4 + DoubleAngleRefl + HHH
UHF+Hi-VHF HFF8, a Horizontal Stack of 2 ea Free-Form 4-Bays (FF4) with Double Angle Reflectors
(each 48" H x 36" W using 2x2-in Grid) and HHH (Hollands Horizontal Harness) were analyzed using 4nec2.
Essentially all Dimensions were determined using nikiml's Python Optimization Scripts.

Performance was slightly "Better" at THREE notable Stacking Distances:
34.821-inches (NO GAP, Continuous Reflector), 35-inches (Metal-to-Metal about 1/4-inch)
and 51-inches, which are analyzed below.
There were notable Stacking Distances further out, but none were particularly "Better".

Although the differences are only a few tenths of a dB, Stack Distance = 51-inches was just
a bit "Better", esp. Hi-VHF, than at 35-inches.  The wider Separation may also be slightly
"Better" at combating Multipath Fading due to the reduction in Statistical Correlation
between the two Antenna signals.  The "NO GAP between Reflector" alternative was slightly worse.

===========================================
a) Horizontal Stacking Distance (4-Bay Center-to-Center) = 34.821 inches (NO GAP between Reflectors).

T.B.D.

===========================================
b) Horizontal Stacking Distance (4-Bay Center-to-Center) = 35-inches (0.18-in GAP between Reflectors).



===========================================
c) Horizontal Stacking Distance (4-Bay Center-to-Center) = 51-inches (16.18-in GAP between Reflectors).
114 Visits
42 Images
Linked Album
holl_ands
Joanne's Cookies
19. Joanne's Cookies  (October 16, 2014)
106 Visits
22 Images
Linked Album
limafamily
20. UHF Batwing - No & 11RR  (16 Oct 2014)
UHF Batwing Antenna with No Reflector and 11 Reflector Rod Screen analyzed using 4nec2.  Based on 4nec2 files provided by user <300ohm>.
0 Visits
0 Images
Linked Album
holl_ands
UHF 4-Square Chireix Free Form
21. UHF 4-Square Chireix Free Form  (15 Oct 2014)
4-Square Chireix Free Form (Unequal Inner/Outer Lengths & Angles) Antenna with NO Reflector and 11 Reflector Rods analyzed using 4nec2.
550 Visits
27 Images
Linked Album
holl_ands
Displaying Copper Roses
22. Displaying Copper Roses   (October 2014)
My Copper Roses often are given as Wedding gifts,  7th Anniversary, Christmas, Valentine's Day, Mothers' Day, and Birthdays and as symbols of affection.
These patrons have sent me photos of my copper roses in situ.
http://www.joygibat.com/
6773 Visits
48 Images
Linked Album
joygibat
MCSQG
23. MCSQG   (10/1/14)
January BOM.
Theme:  calendar quilt
Techniques:  Applique, padded appliqué, hand or machine embroidery
397 Visits
16 Images
Linked Album
puppys2852
HIVHF+UHF VEE Folded Dipole
24. HIVHF+UHF VEE Folded Dipole  (25 Sept 2014)
Hi-VHF+UHF "VEE" Folded Dipole analyzed using 4nec2.
1323 Visits
27 Images
Linked Album
holl_ands
VHF Simple-VEE-Rabbit-Ears
25. VHF Simple-VEE-Rabbit-Ears  (14 Feb 2011)
VHF Simple-VEE-Rabbit-Ears (no matching network) analyzed using 4nec2.

Hi-VHF Band Optimum Whisker Length = 14.75 for Quarter-Inch-Copper-Tubing (QICT) with Feedpoint Gap = 0.75-in.

For 45-degree Angle, Horizontal Polarization Gain was equal to Vertical Polarization Gain across the Hi-VHF Band.

Note: Even a 0.5-inch error in adjusting lengths of Rabbit Ears severely degraded SWR, although only minor impact on Raw Gain.

EDIT (10Sep2011): Added a "What-IF" exercise to illustrate the Raw Gain and SWR (if 300-ohms) from Ch2-13.
Note that SWR in Hi-VHF Band is four time higher than for 75-ohms, and becomes even more excessive on lower freqs,
as the Impedance becomes nearly all Capacitance (negative Reactance).

EDIT (16Jan2012): Added Circular Polarization Azimuthal Plots.  Note that Right Circular = Left Circular at 90-deg & 270-deg Azimuths, so there is very little suppression of Cross-Polarized (e.g. reflected Multipath) signals.

ERRATA (5Sep2014): Uploaded revised 4nec2 File with sin and cos functions reversed to match Angle Definition in Comment description.  Since all charts were for 45-degree Angle, they are NOT affected.
951 Visits
24 Images
Linked Album
holl_ands
UHF Vert 8-Bay Dipole + 43 Pair RR - OPT
26. UHF Vert 8-Bay Dipole + 43 Pair RR - OPT  (1 Sep 2014)
UHF Vertical 8-Bay FAT Dipole with 43 Pairs of Reflector Rods analyzed using 4nec2 after
determining Dimensions using nikiml's Optimization Scripts.
741 Visits
15 Images
Linked Album
holl_ands
UHF 3-Bay FAT Dipoles + 12 Pair RR - OPT
27. UHF 3-Bay FAT Dipoles + 12 Pair RR - OPT  (1 Sep 2014)
UHF 3-Bay FAT Dipoles with 12 Pair of Reflector Rods (narrow Gap in the middle) analyzed using 4nec2 after determining Dimensions using nikiml's Python Optimization Scripts.
709 Visits
21 Images
Linked Album
holl_ands
UHF Cir-Pol 5-Blade Fan
28. UHF Cir-Pol 5-Blade Fan  (29 Aug 2014)
UHF Circularly Polarized 5-Blade Fan analyzed using 4nec2.
774 Visits
48 Images
Linked Album
holl_ands
UHF 3-Bay Fat Dipole + 16 RR - OPT
29. UHF 3-Bay Fat Dipole + 16 RR - OPT  (21 Aug 2014)
UHF 3-Bay Fat Dipole + 16 Reflector Rods analyzed using 4nec2 after determining dimensions
using nikiml's Python Optimization Scripts.  Reflector Rod-to-Rod Separation was presumed
to be 2-in for an existing set of 4 ea Reflector Sub-Assemblies with 4RR each.
704 Visits
24 Images
Linked Album
holl_ands
A-C U8000 8-Bay - 9 Full-Width Refl Rods
30. A-C U8000 8-Bay - 9 Full-Width Refl Rods  (18 May 2013)
Antennacraft U-8000 8-Bay Bowtie, modified for 9 FULL-WIDTH Reflector Rods analyzed using 4nec2
(eliminated 1/4-in Gap between each Pair of Reflector Rods).

Modification reduced F/B & F/R Ratios.

Dimensions from a 4nec2 file posted by 300ohm in April 2011.
979 Visits
20 Images
Linked Album
holl_ands
 
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