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Requiring a choking balun to isolate the potential RF pick up on the coax
cable as it runs past equipment such as computer within the radio room
at lower HF and MF frequencies a simple method of
winding RG58 coax onto a
Powdered Iron Toroid Core was constructed.
Figure 1 Schematic of the 1:1 choking balun
Construction
The
construction was simply to wind as many turns of RG58 coax onto the T250-26
Powdered Iron Toroid Core as would fit. The result of 23 turns
achieved a 130uH series inductive reactance to common mode RF currents.
Parts
list.
- T250-26
Powdered Iron Toroid Core (Micro Metals)
- About 3mtr of RG58
coax.
- 2 x N type chassis
mount connector
- Sealed
Polycarbonate Enclosures 165 x 125 x 75mm
Photo
1 Low
band choking balun
assembled.
Testing
The AIM 4170C antenna analyser recorded a 130uH inductive reactance
with intertwining capacitance resulting in a series resonates at approximately
3.2MHz. Figure 2 show the inductive reactance as measured in the coax
shield presents acceptable reactance from approximately 1.8MHz to
about 10MHz.
Figure
2 The evaluation of the choking impedance of the balun over a bandwidth
from 10 kHz- 2 MHz
Figure
3 The evaluation of the balun with a 50 ohm load over a bandwidth
from 100 kHz- 30 MHz. The balun is shows increasing SWR against
increasing frequency from the ideal 1:1.
Figure
4 The evaluation of the balun with a 50 ohm load over a bandwidth
from 100 kHz- 30 MHz. The balun is shown to introduce some capacitive
reactance from the ideal load.
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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