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 holl_ands | Home > Bowties, Dipoles, Batwings & Rhombics > 
VHF Stick Dipoles incl Horiz.Rabbit-Ears
VHF Stick Dipoles of various Length Elements (3/8-in Diameter & 1/4-in Rabbit-Ears in Horizontal configuration)
analyzed using 4nec2.  Overall-Lengths of the longer Stick Dipoles are typical for VHF/UHF Combo Antenna widths.

Note that when matched to the "natural" dipole impedance of 75-ohms, SWR is very narrowband.
Better wideband performance is found when terminate into 300-ohms.  [Raw Gain is unaffected.]

For Ch2 (57 MHz center freq), it's necessary to match a Total Length of 98.5 inches to 75-ohms,
since 300-ohm load yields Excessive SWR.  The resultant Antenna has just barely enough
low SWR bandwidth for Ch2 and should be located at least several inches away from nearby
objects, whether metal or not, to prevent detuning the Antenna.
For Ch3, best Total Length would be 86.25-inches, with similar results, when matched
into 75-ohms [direct connect Coax to Center of Dipole].

For the Ch2 & Ch3 narrowband antennas, wire as small as AWG12 provided acceptable SWR
and same Gain as 3/8-in Aluminum.  Twinlead with AWG24 not recommended for Ch2-4 due to poor SWR.

Many/most Rabbit-Ear Antennas can not be extended enough to provide acceptable (under 2.7) SWR on Ch2 & Ch3.
"Best" Gain (only 2 dBi) & SWR (Excessive, under 5) for Hi-VHF Band is when Half-Lengths = 14.5-inches.
Impedance Matching Networks in the Rabbit-Ears base can improve on this SWR...unfortunately
manufacturers' don't want to disclose specs....so don't  expect much of an improvement....

EDIT (16Jun2013): Added Total Length = 98.5 inches for Ch2, matched to 75-ohms, including an example 4nec2 File.

ERRATA (16Jun2013): Corrected "Half-Lengths" to "Overall-Length" in labels on all except first image,
which correctly uses "Half-Lengths" when describing Rabbit-Ears.
Date(s): 24 Nov 2012. Album by holl_ands. 1 - 21 of 21 Total. 8488 Visits.
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Enlarge photo 1
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1
VHF Stick Dipole - Different Sizes for
Rabbit-Ear Half-Lengths (1/4-in Diameter)
Raw Gain & SWR (300-ohms)


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2
Stick Dipole - 3D View
Generic - Same for any Size


Enlarge Microsoft Word Document 3
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DOC3
VHF Stick Dipole
Overall Length = 98.5-in for Ch2 (ONLY)
4nec2 File


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4
VHF Stick Dipole
Ch2-13 Raw Gain best on Ch7-13
Overall Length = 37.5-in Optimum for Ch7-13.

FYI: Max possible with RCA ANT110 Rabbit Ears
when extended in Horizontal position.


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5
VHF Stick Dipole
Ch2-13 SWR (75-ohms)
Overall Length = 37.4-in Optimum for Ch7-13
Low SWR only for a narrow band near resonance.


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VHF Stick Dipole
Ch2-13 SWR (300-ohms)
Overall Length = 37.4-in Optimum for Ch7-13

SWR too high on Ch2-4


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VHF Stick Dipole
Ch2-13 Raw Gain
Overall Length = 89-in

Gain Loss across Ch7-13


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VHF Stick Dipole
Ch2-13 SWR (75-ohms)
Overall Length = 89-in
Low SWR only for a narrow band near Ch3 resonance
AND near 194 MHz.


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9
VHF Stick Dipole
Ch2-13 SWR (300-ohms)
Overall Length = 89-in

SWR too high on Ch2


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10
VHF Stick Dipole
Ch2-13 Raw Gain
Overall Length = 95-in

Gain Loss across Ch7-13


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VHF Stick Dipole
Ch2-13 SWR (75-ohms)
Overall Length = 95-in
Low SWR only for a narrow band near resonance
AND near 180 MHz.


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12
VHF Stick Dipole
Ch2-13 SWR (300-ohms)
Overall Length = 95-in

SWR a bit high on Ch2-6


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13
VHF Stick Dipole
Ch2-13 Raw Gain
Overall Length = 110-in

Gain Loss across Ch7-13


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VHF Stick Dipole
Ch2-13 SWR (75-ohms)
Overall Length = 110-in
Low SWR only for a narrow band near resonance
AND near 156 MHz.


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15
VHF Stick Dipole
Ch2-13 SWR (75-ohms)
Overall Length = 110-in

SWR a bit high on Ch2-6


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VHF Stick Dipole using 3/8-in Alum.
Raw Gain = 2.1 dBi on Ch2
Overall Length = 98.5-in best for Ch2 (ONLY)


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17
VHF Stick Dipole using 3/8-in Alum.
SWR (75-ohms) Under 2.06 on Ch2
Overall Length = 98.5-in best for Ch2 (ONLY)


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18
VHF Stick Dipole using 3/8-in Alum.
SWR (300-ohms) is Excessive on Ch2
Overall Length = 98.5-in best for Ch2 (ONLY)


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VHF Stick Dipole using AWG-12
Raw Gain = 2.1 dBi on Ch2
Overall Length = 98.5-in best for Ch2 (ONLY)


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VHF Stick Dipole using AWG12 Copper
SWR (300-ohms) Under 2.6 on Ch2
Overall Length = 98.5-in best for Ch2 (ONLY)


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21
VHF Stick Dipole using AWG-12 Copper
SWR (300-ohms) is Excessive on Ch2
Overall Length = 98.5-in best for Ch2 (ONLY)


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