BALUN ang.pdf
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915 KB
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Pobierz
Jacques Audet
VE2AZX
VE2AZX@amsat.org
Nov. 2006 Rev.1 June
VE2AZX
1
- 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
2
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
3
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
4
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
5
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