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 holl_ands | Home > Multi-Bay Bowtie Antennas > UHF 4-Bay Bowties with Reflector > 
UHF Actual CM4221 Flat Bows & Reflector
Channel Master CM4221 4-Bay (8.5x8.9) Bowtie Antenna (with Reflector Screen) analyzed using 4nec2.
Measurements verified against a photo posted by mclapp:
http://www.frontiernet.net/~mclapp/Antennas/CM4221/CM4221%20front.jpg

BowLength = 8.5-in, Bowtie Spacing = 8.9-in, Tine Separation = 5.25-in. All AWG8.
Feedline Separation = 1.4-in, with 0.8-in at Crossover.  All AWG8 wire size (0.125" O.D.).
Center of Crossovers 2.75-in from Center of Outer Bowties.
Screen Reflector (36"H x 20"W).  Separation from Bowties = 4.5-in.

Gain increases from 12.2 to 14.9 dBi at 698 MHz.  SWR is mostly under 2.0, climbing as high
as 3.3 at 470 MHz, which results in minor Net Gain loss at Low Freqs.

If the Crossovers were moved from their current location (2.75-in away from Outer Bowties),
so that they are Centered between the Bowties (as is done in some UTube 4-Bays), the Gain
at the highest frequencies is significantly reduced with about a 1 dB loss in F/B Ratio.  The SWR
at Low Freqs also increases, resulting in an additional 1 dB Net Gain loss at 470 MHz.

Results for Ken Nist's CM4221a.ez file are also included in the comparison Charts, showing minor Raw Gain
loss vs the ACTUAL CM4221, higher SWR (reducing Net Gain at low freqs) and a higher F/B Ratio.
Date(s): 27Aug2009. Album by holl_ands. 1 - 17 of 17 Total. 5608 Visits.
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CM4221 4-Bay Gain Chart:
IF Crossovers were Centered between Bowties,
Gain is significantly reduced (esp for Ch57-69)
and F/B Ratio is reduced by about 1 dB.


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CM4221 4-Bay SWR Chart:
In Actual CM4221, Crossovers are much closer
to the Outer Bowties.


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DOC3
CM4221 Actual w Reflector - 4nec2 File
SYmbols make it easy to vary parameters.


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CM4221 Actual - 3D View

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CM4221 Actual - Front View
[One small box = 0.5 inch]


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CM4221 Actual - Top View
[One small box = 0.5 inch]


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CM4221 Actual - UHF Raw Gain

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CM4221 Actual - UHF SWR (300-ohm)

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CM4221 Actual - UHF Impedance

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CM4221 Actual - UHF Raw Gain
IF Crossovers were Centered between Bowties


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CM4221 Actual - UHF SWR (300-ohm)
IF Crossovers were Centered between Bowties


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CM4221 Actual - UHF Impedance
IF Crossovers were Centered between Bowties


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CM4221 Actual - Hi-VHF Raw Gain
TOWARDS THE REAR DIRECTION

At Hi-VHF there is MORE GAIN towards the Rear


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CM4221 Actual - Hi-VHF Raw Gain
TOWARDS THE FORWARD DIRECTION


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CM4221 Actual - Hi-VHF SWR (300-ohm)
Excessive SWR, although Ch9-11 are lowest


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CM4221 Actual - Hi-VHF Impedance

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CM4221 Actual - Side View
[One small box = 0.5 inch]


 
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