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Requiring
a balun to feed a balanced feed line from an un-balanced T-Match
tuner, a 1:4 Guanella Current
balun design using a
single FT240-43
ferrite toroid cores was selected.
An impedance transformation
balun is required due variations in impedances that are nearly always
on the higher side of the nominal 50 ohms when feeding a multi-band balanced antenna system. The balun may be required to
sep up the feed impedance presented at the T-Match tuner to
improve the matching range.
Construction
The
1:4 current balun consists
of two double bifilar winding of 11.5 turns wound evenly
spaced around the FT240-43
ferrite toroid core as shown in figure 2.
Figure 1 Schematic of the 1:4 Guanella Current
balun.
| Type |
Impedance
transformation |
| Ratio |
1:4 |
| Frequency Range |
1.5 ~ 30MHz |
| Core Used |
FT240-43 Ferrite
Toroid Core |
| Number of turns |
a = 11.5 tuns plus b =
11.5 turns |
| SWR |
1.2:1 or less. Ref:
Figure 3 |
Figure 2 Wiring of the 1:4 Guanella Current
balun.
Note
this drawing shows winding connections and not the number of turns
required. See article for details.
Parts
list.
-
1
x FT240-43 ferrite toroid core.
-
4
x 800mm of PTFE silver plated copper wire, 1.0mm, AWG 18, WHITE
Testing
The AIM 4170C antenna analyser recorded the balun impedance
transformation efficiency a for a frequency
range from 1.0MHz to 30MHz.
The evaluation of the efficiency
of the balun over the desired bandwidth (1.0 - 30MHz) was carried out
by testing the impedance that could be seen from
unbalanced side to a resistive load applied to the balanced side of
the balun using
a AIM 4170C antenna analyser. The efficiency is shown to be relatively flat from below
1.0MHz
to above 30MHz. The below antenna analyser
plot viewing a 200ohm resistive load attached to the balanced
side of the balun and measured at a nominal impedance of 50ohms
presented as anticipated an approximate 50ohm load to the analyser and
ideally produced about a
1:1 SWR. The results are a little higher than expected, however demonstrates
that the balun's 1:4 current transformation occurs reasonably efficiently from
well below 1.0
to beyond 30MHz
Figure 3
AIM 4170C antenna analyser
plot viewing a 200ohm resistive load through the Guanella
current
balun.
Note the 200ohm resistor appears as 50ohms due to the 1:4 balun ratio
resulting in an ideal SWR of 1:1. This plot shows an SWR ranging
from 1.0:1 to about 1.2:1
Figure 4
AIM 4170C antenna analyser
plot viewing a 200ohm resistive load through the Guanella
current
balun.
Note the 200ohm resistor appears as 50ohms due to the 1:4 balun ratio. The
Rs (Resistive load) tracks closely with Zmag as would be hoped with
the Xs (Reactive load) being relatively low.
Also
see other baluns and ununs:
BALUN
1:1 CHOKE & 1:4 BALUN HF
ladder feed-line to coaxial cable combination choke and 1:4 balun.
(0.1MHz - 30MHz).
BALUN
1:1 CHOKING Choking balun
for lower HF and MF bands. (200kHz - 10MHz).
CHOKING
1:1 BALUN - HF BANDS Reisert
choking balun.
(1.0MHz - 30MHz). FT240-43 Ferrite Toroid Core.
CHOKING
1:1 BALUN - HF BANDS Reisert
choking balun
(1.5MHz - 30MHz). FT140-43 Ferrite Toroid Core.
CHOKING
1:1 BALUN - LOW VHF BAND Choking balun.
(10MHz - 60MHz). FT140-43 Ferrite Toroid Core.
BALUN
1:1 CURRENT 1:1
Guanella
Current
balun
using a L15 ferrite core (1.8 - 30MHz).
BALUN
1:4 CURRENT 1:4
Guanella
Current
balun
using a L15 ferrite core (1.8 - 30MHz).
BALUN
1:4 SINGLE CORE CURRENT 1:4 Guanella
Current Balun, single FT240-43
ferrite toroid cores.
(0.3MHz - 30MHz).
BALUN
1:1 VOLTAGE 1:1 Ruthroff
voltage balun using a T-200-2
powdered iron toroid core (1.8 -
30MHz).
BALUN
4:1 VOLTAGE 4:1 Ruthroff
voltage balun using a T-200-2
powdered iron toroid core (1.8 -
30MHz).
BALUN
6:1 VOLTAGE - VERSION 1 6:1
Voltage balun using a L15
ferrite toroid core (1.8 - 30MHz).
BALUN
6:1 VOLTAGE - VERSION 2 6:1
Voltage balun using a FT140-43
Ferrite Toroid Core (1.8 - 30MHz)
BALUN
9:1 VOLTAGE - VERSION 1 9:1
Voltage balun using a L15
ferrite toroid core (1.8 - 30MHz).
BALUN
9:1 VOLTAGE - VERSION 2 9:1
Voltage balun using a FT140-43
Ferrite Toroid Core (0.5 - 60MHz).
UNUN
9:1 VOLTAGE 9:1 voltage unun
using a
T-200-2 powdered iron toroid
core
(1.8 -
30MHz).
UNUN
9:1 VOLTAGE VERSION 2 9:1 voltage unun
using a L15 ferrite core (1.8 -
30MHz).
UNUN
9:1 VOLTAGE VERSION 3 9:1 voltage unun
using a FT140-43 ferrite core (0.5 -
60MHz).
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