Balun Design using Chokes

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Balun Design using Chokes

• David Conn VE3KL

6 Metre Choke
RG8-X
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Acknowledgements

• QCWA Chapter 70 Members
• Dave Green VE3TLY
• Ben Price VE3CDA
• Doug Leach VE3XK
• Ray Parsons KG2B

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Background on BalunsBalanced-to-UnbalancedTrans
mission Line TransformersBasic TYPES

• Choke type.. a simple coil of coax..my talk
• Ferrite Core Ruthroff, Guanella designs
• Ferrite Beads over the coax
• Bazooka. Quarter wave coupling stubs

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Purpose of the Talk

• To show what a Choke does for you
• To give you the actual design information

All Design Information in the RAC Web Site and
TCA Jan/Feb 2007

• RAC Hotlinks 2007 Jan-Feb
• RAC Calculators (VE3KL Coil Calculator)

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The Problem
Uncontrolled Antenna Pattern
RF in Radio Shack
SWR?
Television Interference
Unwanted Radiation
Power line noise
Noise Received From Vertically Polarized Sources
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SWR with a Choke
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SWR Without a Choke
EZNEC Simulation
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The SolutionA Good Choke
Isolation Plane
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How is a Good Choke Designed ?(Not by using
10 turns of coax with a diameter of 6 to 8
inches!)
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VE3KL Coil Design Calculator
Coil Theory Inductance Maxwell 1873 Skin
Effect Lamb 1883 Inductance Wheeler
1928 Capacitance Grandi 1999 Insulator
Thickness Length Diameter Nr. Turns Pitch
Air Core Design
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Frequency Response of the Choke
Ideally, put the resonant peak in the band center.
21 MHz
Keep the Coil Reactance Greater Than 1500 Ohms
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VE3KL Design Graphs/TablesThree Methods

• Select a single band design dimensions not
  fixed.a compromise
• Select a single band optimized designdimensions
  fixed
• Select a multi-band designdimensions fixed a
  compromise

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Example of A Single Band Design15 Metres
20 Turns, 56 mm
Reactance Greater Than 1500 Ohms
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Example of A Single Band Design..2 Metres
10 Turns,53 mm
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Examples of Single Band Optimized Designs
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Examples of A Multi Band Designs
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Which Design?

• Select the Single Band design when size is
  important..my Hamstick 20 m Dipole
• Select an Optimized Single Band Design when
  performance is paramount not Size.a Mono Band
  Beam
• Select a Multi Band Design for your Tri Band Beam
  and others

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Coaxial Cable Issues ?

• MIL Spec and Amateur Types
• Bending Radius
• Waterproof ? Connectors?
• Specifications not complete
• Foam core vs. solid core
• Dielectric properties of the outer jacket?

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Summary?

• Chokes Clean up your antenna system
• Many Designs available on the RAC Web Site
• Models use state of the art algorithms
• MF Chokes get very large
• VHF Chokes get small
• Transmission Line Chokes needed for UHF and above

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Mr. Problem
NO
Uncontrolled Antenna Pattern
RF in Radio Shack
SWR?
Wanted for recycling
Television Interference
Power Line Noise
Noise Received From Vertically Polarized Sources
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VY 73David VE3KL
Build One for Your Next Antenna