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Baluns and Ununs

Baluns and Ununs. What Are They?. Balun = Bal anced Un balanced Current - forces symmetrical current on terminals Current determines radiation pattern Voltage – forces symmetrical voltage on terminals Less efficient, less common Unun = Un balanced Un balanced

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Baluns and Ununs

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  1. Baluns and Ununs

  2. What Are They? • Balun = Balanced Unbalanced • Current - forces symmetrical current on terminals • Current determines radiation pattern • Voltage – forces symmetrical voltage on terminals • Less efficient, less common • Unun = Unbalanced Unbalanced • Transmission line transformers

  3. What Is Balanced vs Unbalanced? • Balanced Load – ladder line • Unbalanced Load - coax I1 I2 I3* *I3 = common-mode current is greatest at multiple of ½ λ

  4. Types of Baluns • Voltage or Current Transformer • Torroid core • Ferrite • Powdered Iron • Rod core • Current Choke • Air Wound • Scramble • Form • Bead • Torroid

  5. Types of Baluns Air Core – scramble wound Choke - Bead

  6. Types of Baluns Torroid– ferrite Choke - Bead

  7. Types of Baluns/Ununs Torroid– ferrite Yaesu FC-40 AMU (unun) L-R: 1:1 current balun, 4:1 voltage balun, 1:1 current unun

  8. Uses for Baluns and Ununs • Balun • OCF dipole • Yagi • Windom • G5RV • Unun • Vertical • Long wire • Loop

  9. Uses for Baluns and Ununs

  10. Uses for Baluns and Ununs

  11. The Project • HF antenna capable of multi-band operation • Off-Center-Fed (OCF) dipole looked good – tuner not required • OCF presents 200 Ω impedance • Needed a 4:1 current balun to transform 200Ω to 50 Ω • Articles by Jerry Sevick, W2FMI (SK) • Amidon Associates

  12. The Project

  13. W2FMI 4:1 –HBM200 Balun • FT-240-K ferrite core • two 14 AWG bifilar windings, 100-ohms each • 15-mil teflon sleeve • 1MHz – 50MHz range • 2KW continuous • 4KW peak • 98% efficiency

  14. Finished Product

  15. Test Results* * Two 100 Ω resistors in series used to simulate load

  16. Next Step 4:1 balun 2/3 1/3 coax 1:1 line isolator Yaesu 897D

  17. Sources • “Baluns: What They Do And How They Do It”, Roy Lewallen W7EL, ARRL Antenna Compendium, Vol. 1. • “Transmission Line Transformers Handbook”, Jerry Sevick W2FMI. • “The ARRL Antenna Book For Radio Communications”, 22d Edition, ARRL. • “The ARRL Handbook For Radio Communications”, 88th Edition, ARRL. • “More On The 1:1 Balun”, Jerry SevickW2FMI, CQ, April 1994 • Amidon Associates, http://www.amidoncorp.com • Palomar Engineering, http://www.palomar-engineers.com

  18. Questions?

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