Shunt Fed Tower
Z
=
440
+
j300
Or
If You Have a 50- to 60-Foot Tower with
Something on Top, Here’s One Way
You Can Get on 160M
My Situation
 City Lot
 Tribander for 10, 15, and 20M
 Full-wave Delta Loop for 40M
 What to do for 160M?
Use Existing Tower
http://www.qsl.net/w9rb/webdoc9.htm
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
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
Model
 EZNEC+ Version 5.0
 f=1.825 MHz Z=27.59 + j556
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
160M Shunt Fed 60-Foot Tower
Measured
 Autek Research RX VECTOR
ANALYST Model VA1
 f=1.825 MHz Z=440 + j300
Matching Network
http://www.circuitsage.com/matching/matcher2.html
L = 15 uH C = 558 pF
Matching Network
Source --------- L = 15 uH ----------- Load
|
C = 558 pF
|
Gnd
On The Air
 Works okay for transmit
 Not so great for receive
Possible Problem
 Rotor in tower – controller may not be happy
 Solution disconnect rotator control cable before
transmitting