BALUN ang.pdf

Jacques Audet

VE2AZX

VE2AZX@amsat.org

Nov. 2006 Rev.1 June

VE2AZX

- REASONS FOR USING A BALUN

- TYPES OF BALUNS

- CHECK YOUR BALUN WITH AN SWR ANALYZER

- MESURING THE IMPEDANCE OF A NUMBER OF FERRITES

- IMPEDANCE MEASUREMENT RESULTS

- USING FERRITES ON A FEEDER AND HOUSE CONDUCTORS

Nov. 2006 Rev.1 June

VE2AZX

REASONS FOR USING A BALUN ?

BALUN = BALanced to Unbalanced - It’s a transformer

Used to feed a balanced load, Ex: dipole

Decreases feeder radiation

The feed line becomes independent of the antenna:

We can change its length … move it around

Without causing SWR change.

Nov. 2006 Rev.1 June

VE2AZX

REASONS FOR USING A BALUN ?

DIPOLE

With a balun, radiation picked up by the

feeder from each side of the dipole

cancels at the feeder.

Decreases feedline current.

The feedline’s outer shield becomes

”floating” and independent of the antenna.

The feedline should run away from

the dipole at right angle.

The dipole should be parallel to the

ground.

A non symetrical antenna Ex: Windom…

Will require the use of a current balun

Nov. 2006 Rev.1 June

VE2AZX

BALUN TYPES

VOLTAGE

- TRANSFORMER WITH WINDINGS GIVING A BALANCED OUTPUT

- IN-OUT IMPEDANCES ARE DETERMINED BY THE TURNS RATIO.

A WIDE RANGE OF RATIOS IS POSSIBLE.

- OPERATES OVER A SOMEWHAT LIMITED BANDWIDTH (100 TO 1)

CURRENT

- USES TRANSMISSION LINES WOUND ON A CORE

- MAY USE A COAXIAL CABLE OR A PARALLEL WIRE LINE WITH OR

WITHOUT FERRITES.

- COMMON IMPEDANCE RATIOS: 1:1 AND 4:1

- OPERATE OVER A MUCH WIDER BAND OF FREQUENCIES

Nov. 2006 Rev.1 June

VE2AZX

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