RADIO - ANTENA - HOBBY

Nov. 2006 VE2AZX 2
-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

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.




REASONS FOR USING A BALUN ?With a balun, radiation picked up by thefeeder from each side of the dipole cancels at the feeder. Decreases feedline current.BALUN+-DIPOLEThe feedline becomes ”floating” andBecomes 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


TYPES DE BALUNVOLTAGE
-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