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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  

 

Type  Choking Balun
Ratio 1:1
Frequency Range 14 ~ 54MHz
Choking Impedance 2k Ohms minimum. Ref: Figure 3
Core Used FT140-43 Ferrite Toroid Core
Number of turns 8 (4 + 4). Ref: Figure 2
SWR 1:1 Ref: Figure 4

 

 

 

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.

  • FT140-43 Ferrite Toroid Core
  • About 0.3mtr of RG174 coax.
  • 2 x N type chassis mount connector
  • 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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Page last revised 06 February 2022  
 

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