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Tag Archives: balun

The 9:1 Balun

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During my recent holidays in Sardinia I’ve been experimenting some portable wire antennas.

Since some years to now, I use to bring with me just a 10m fishing pole and some wires. This year I’ve decided to take with me some thoroids, copper cable, and a solder… and homebrew a balun.

One of the balun I’ve used is the 9:1 balun, an impedance transformer to feed a high impedance, end fed random wire antenna connected to my fishing pole.

These are some schematics I’ve used as reference

 

9:1 antenna-balun

 

 

 

 

 

I’ve used a T-200 thoroid for my 9:1 Balun, thin copper cable, and a PL coax connector.

 

Simple HF Baluns for 50/75 Ohm Systems

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The following diagrams and tables show some simple 1:1 and 4:1 baluns for use between 1.8 and 30 MHz using twin transmission lines made from enamelled copper wire (ecw). The bifilar windings have been adjusted (spacing) to produce transmission lines with Zo of 50 or 75 ohms as required for best matching. These designs should be suitable for 100-200 Watt operation.

RF transformers should always operate within safe limits of temperature and linearity. The following designs which use toroid cores can be checked for safe operating conditions with the programs included in Programs.

Materials required:

  • Ferrite Core: Select either rod or toroid core as detailed below
  • Core insulation: 1 layer of ptfe tape (plumbers thread sealing tape); plumbing and hardware suppliers
  • Wire: 1.0 or 1.25mm enamelled copper wire (ecw) as specified; electronics shops
  • Spacing material: Kinnears 540 TEX colourfil twine; product code K 069048; newsagents, craft suppliers
  • Note: This spacing material is polypropylene; other material is probably suitable, but ensure it will not absorb moisture.

Winding Methods

bifil_winding_1 Continue reading→

Step-By-Step Construction of a 4:1 Current-Type Balun

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Article by Charles Greene, W1CG

My 4:1 current-type balun is wound on a FT-114-43 core. The FT-140-43 is a little easier to
work with, and maybe the FT-140-77 would cover 160-10. This one is reasonably flat from 4.5
to 35 MHz but drops off a little at 3.5, 40-ohms with a 200 ohm resistor on the high side instead
of the 50-ohms I get on the higher bands.
The reason I used the R/S speaker wire is that last summer Wayne (N6KR) reported his
double Zepp with a R/S speaker wire feed line, and someone at ARRL lab measured the
impedance and came up with around 120 ohms. You are supposed to use something that has
an impedance of approximately 2X the input impedance, and this was close.
Now, to the construction instructions:
Refer to the schematic (or figure 2-1A on page 18 of Jerry Sevick’s book “Building and Using
Baluns and Ununs”).

Continue reading→