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CHOKING BALUN FOR
LOW BAND VHF
Choking balun for upper HF to lower VHF bands. (10MHz - 60MHz).
Requiring a choking balun to isolate the potential common mode RF on the coax
cable for a new 6m band Ringo 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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14 ~ 54MHz
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Choking Impedance
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2k Ohms minimum. Ref:
Figure 3
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Core Used
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FT140-43
Ferrite Toroid Core
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Number of turns
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8 (4 + 4). Ref:
Figure 2
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SWR
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1:1 Ref: Figure 4
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Figure
2 Winding details of the 1:1 choking balun
Construction
The
construction was simply to wind 8 turns of RG174 coax onto a FT140-43
Ferrite Toroid Core. The result of 8 turns
achieved an average of 40uH lumped value inductive reactance to common mode RF
currents from approximately 10MHz to 70MHz.
Parts
list.
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FT140-43
Ferrite Toroid Core
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About
0.3mtr of RG174 coax.
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2 x N type chassis
mount connector
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Sealed
Polycarbonate Enclosures
82 x 80 x 55mm
Photo
1
Low band choking balun assembled.
Photo
2
Rear view of the Low band choking balun assembled showing the hose clamp mast attachments.
Testing
The AIM 4170C antenna analyser recorded in Figure 2 show the
Impedance as measured in the coax
shield presents an acceptable 2000 Ohms or greater from 14MHz to
about 54MHz.
Figure
3 The evaluation of the choking impedance of the balun over a bandwidth
from 10MHz- 60MHz.
Figure
4 The evaluation of the balun with a 50 ohm load over a bandwidth
from 10MHz- 70MHz. The balun shows a very low SWR from the ideal
1:1 and despite the visual appearance in the graph this result is
almost perfect and flat.
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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last revised 05 May, 2025
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