Shunt Fed Tower
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Transcript of Shunt Fed Tower
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Shunt Fed Tower
OrIf You Have a 50- to 60-Foot Tower with
Something on Top, Here’s One WayYou Can Get on 160M
Z = 440 + j300
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My Situation
City Lot Tribander for 10, 15, and 20M Full-wave Delta Loop for 40M What to do for 160M?
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Use Existing Tower
http://www.qsl.net/w9rb/webdoc9.htm
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Why a Vertical?
Low take-off angle for DX Not a “space-saving” antenna Needs radials – the more the better Real World - 16 radials MINIMUM Ten 10-foot radials better than one 100-foot
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Construction
Two wires 18 inches apart – fat conductor Inside wire 3 feet from tower Gamma section as long as possible Weather-proof plastic box at base
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Model
EZNEC+ Version 5.0 f=1.825 MHz Z=27.59 + j556
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EZNEC+ ver. 5.0
160M Shunt Fed 60Ft Tower
--------------- SOURCE DATA ---------------
Frequency = 1.825 MHz
Source 1 Voltage = 556.7 V at 87.16 deg. Current = 1 A at 0.0 deg. Impedance = 27.59 + J 556 ohms Power = 27.59 watts SWR (50 ohm system) > 100
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160M Shunt Fed 60-Foot Tower
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Measured
Autek Research RX VECTOR ANALYST Model VA1 f=1.825 MHz Z=440 + j300
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Matching Network
http://www.circuitsage.com/matching/matcher2.html
L = 15 uH C = 558 pF
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Matching Network
Source --------- L = 15 uH ----------- Load
|
C = 558 pF |
Gnd
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On The Air
Works okay for transmit Not so great for receive
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Possible Problem
Rotor in tower – controller may not be happy Solution disconnect rotator control cable before transmitting