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CHOKING BALUN FOR
HF BANDS
Choking balun
for HF and upper MF bands. (1.5MHz - 30MHz).
Requiring a choking balun to isolate the potential feed-line common mode RF on the coax
cable for HF/MF bands
1.5MHz - 30MHz. A simple coax cable wound on to a ferrite toroidal core was
chosen.
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Prevents
unwanted RFI by eliminating feedline common mode currents and
radiation
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All
power goes to the antenna, improving efficiency
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Reduces
noise or EMI picked-up by your coax shield
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Power
is balanced between driven elements of antenna
Figure 1 Schematic of the 1:1 choking balun
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Type
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Choking Balun
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Ratio
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1:1
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Frequency Range
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1.0 ~ 30MHz
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Choking Impedance
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1k Ohms (-21dB) minimum. Ref:
Figure 3
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Core Used
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FT240-43
Ferrite Toroid Core
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Number of turns
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14 (7 + 7). Ref:
Figure 2
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SWR
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1:1 Ref: Figure 5
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Figure
2 Winding details of the 1:1 choking balun
Construction
The
construction was simply to wind 14 turns of RG58 coax onto a FT240-43
Ferrite Toroid Core. The result of 14 turns achieved an average of
40uH lumped value inductive reactance to common mode RF currents from
approximately 1.0MHz to 30MHz.
Parts
list.
·
FT240-43
Ferrite Toroid Core
·
About 1.0mtr of RG58 coax.
Photo
1
Choking balun assembled.
Testing
The AIM 4170C antenna analyser recorded in Figure 3 show the
Impedance as measured in the coax
shield presents a minimum of 1000 Ohms from 1.0MHz to
about 30MHz and much greater for the 1.8MHz to 14MHz amateur radio
bands.
Figure
3 The evaluation of the choking impedance of the balun over a bandwidth
from 1.0MHz- 30MHz.
Figure
4 Choking impedance to dB of choking. 20dB attenuation should be considered the minimum.
Figure
5 SWR.from 0.1MHz- 30MHz
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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last revised 05 May, 2025
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