HOME  |  ARTICLESBAND CONDITIONS  |  EQUIPMENT  |  LINK  | MAIL   |  OPERATIONAL  |  PROJECTS  |  REPAIRS & MODS
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:

1:1 Choking balun Choking balun for lower HF and MF bands. (1.8MHz - 10MHz) T250-26 Powdered Iron Toroid Core.

1:1 Choking balun low band VHF Choking balun for lower band VHF. (14 ~ 54MHz) FT140-43 Ferrite Toroid Core.

1:1 Guanella current balun 1:1 Guanella current balun (1.8 - 30MHz) L15 ferrite toroid core.

1:4 Guanella current balun 1:4 Guanella current balun (1.8 - 30MHz) L15 ferrite toroid core.

1:1 Ruthroff voltage balun, 1:1 Ruthroff voltage balun (1.8 - 30MHz) T-200-2 powdered iron toroid core.

4:1 Ruthroff voltage balun  4:1 Ruthroff voltage balun (1.8 - 30MHz) T-200-2 powdered iron toroid core.

6:1 Ruthroff voltage balun  6:1 Ruthroff voltage balun (1.8 - 30MHz) L15 ferrite toroid core.

1:9 voltage unun_v1  9:1 voltage unun (1.8 - 30MHz) T-200-2 powdered iron toroid core. Version 1 

1:9 voltage unun_v2  9:1 voltage unun (1.8 - 30MHz) L15 ferrite toroid core. Version 2

 

 

 

 

TOP OF PAGE

Page last revised 02 October 2019  
 

ACTIVITIES | ARTICLES | EQUIPMENT | HOMELINK | MAIL | PROJECTS

Web design by Peter Miles

All content may be used for unlimited distribution with credits.

This site has been designed to cater for 800 x 600 resolution.
Site is best viewed with Internet Explorer 5.5 or Netscape 6 or higher.