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1:4 GUANELLA CURRENT BALUN - HF

1:4 Guanella Current Balun for HF and  MF bands. (0.3MHz - 30MHz).


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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