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9:1 VOLTAGE UNUN. Version 2

9:1  voltage unun using a L15 ferrite core.


With the view to establish a quick and easy multi-band antenna deployment for portable and camping operations a simple long wire antenna with an earth or earth plus counterpoise arrangement with a 9:1 voltage unun is one possible solution.

Requiring a unun to feed a long wire antenna ideally without a tuner a  9:1 voltage unun design using a L15 ferrite toroid core was selected. 

 

Figure 1  Typical 9:1 voltage unun and long wire antenna configuration.

 

Figure 1  Typical 9:1 voltage unun and long wire antenna configuration.

Construction

 

1.25mm Enamelled copper wire was used in a triple bifilar winding of 4 turns wound evenly spaced around the L15 ferrite toroid core with the three individual windings wound close together.  

 

The length of enamelled copper wire per winding for the L15 ferrite toroid core is determined by length per winding plus tails = 600mm

 

Figure 2  Schematic of the 9:1 voltage unun. Typically unbalanced = 50/75 ohms too unbalanced = 450/675 ohms.

 

 

Figure 3  Wiring of the 9:1 voltage unun

 

 

Parts list.

  • 1 x L15 ferrite toroid core. Jaycar Cat. No. LO-1238

  • Pink heavy duty Teflon plumbers tape.

  • About 3 x 400mm of 1.25mm Enamelled copper wire.

  • Black and Green binding posts.

  • SO-239 UHF chassis mount connector

  • Sealed Polycarbonate Enclosures 82 x 80 x 55mm from Jaycar Cat. No. HB-6230. See Fig 3 for details

Figure 4 Sealed Polycarbonate Enclosures 82 x 80 x 55mm details

 

Photo 1  Completed core winding assembly. note fibre glass tube sections to hold winding groups together. 

 

The evaluation of the efficiency of the unun over the desired bandwidth (1.8 - 30MHz) was carried out by testing the impedance that could be seen from transceiver side of the unun to a resistive load applied to the antenna side of the unun using an antenna analyser.

Figure 5  AIM 4170C antenna analyser plot viewing a 450ohm resistive load through the unun. Note the 450ohm resistor appears as 50ohms due to the 9:1 unun ratio resulting in an ideal SWR of 1:1. 

 

Figure 6  AIM 4170C antenna analyser plot viewing a 100ohm resistive load through the unun. Note the 100ohm resistor appears as 11.1ohms due to the 9:1 unun ratio resulting in an ideal SWR of 4.5:1. 

Figure 7  AIM 4170C antenna analyser plot viewing a 1000ohm resistive load through the unun. Note the 1000ohm resistor appears as 111ohms due to the 9:1 unun ratio resulting in an ideal SWR of 2.2:1. 

AIM 4170C antenna analyser explanation;

SWR

Standing Wave Ratio.

Zmag

Total Impedance.

Theta

Phase angle between voltage and current.

Figure 8  Plot of the Unun losses verses frequency calculated from the AIM 4170C antenna analyser SWR data. The graph shows the worst loss figure between 1.0MHz and 30MHz at -0.2dB at 30MHz, an extraordinarily low figure.

 

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 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

 

References

Martin Ehrenfried G8JNJ experimentation with baluns and ununs see: http://g8jnj.webs.com/balunsandtuners.htm

 

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Page last revised 30 June 2016  
 

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