Baluns and Ununs What Are They Balun Balanced
Baluns and Ununs
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 �Transmission line transformers
What Is Balanced vs Unbalanced? �Balanced Load – ladder line �Unbalanced Load - coax I 1 I 2 I 3* *I 3 = common-mode current is greatest at multiple of ½ λ
Types of Baluns �Voltage or Current Transformer �Torroid core � Ferrite � Powdered Iron �Rod core �Current Choke �Air Wound � Scramble � Form �Bead �Torroid
Types of Baluns Air Core – scramble wound Choke - Bead
Types of Baluns Torroid– ferrite Choke - Bead
Types of Baluns/Ununs Torroid– ferrite L-R: 1: 1 current balun, 4: 1 voltage balun, 1: 1 current unun Yaesu FC-40 AMU (unun)
Uses for Baluns and Ununs �Balun �OCF dipole �Yagi �Windom �G 5 RV �Unun �Vertical �Long wire �Loop
Uses for Baluns and Ununs
Uses for Baluns and Ununs
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, W 2 FMI (SK) �Amidon Associates
The Project
W 2 FMI 4: 1 –HBM 200 Balun �FT-240 -K ferrite core �two 14 AWG bifilar windings, 100 -ohms each � 15 -mil teflon sleeve � 1 MHz – 50 MHz range � 2 KW continuous � 4 KW peak � 98% efficiency
Finished Product
Test Results* SWR Band Frequency 1. 1 160 1. 9 MHz 1. 1 80 3. 9 1. 1 40 7. 2 1. 2 20 14. 2 1. 3 17 18. 1 1. 4 12 24. 9 1. 5 10 29 1. 7 6 52. 5 * Two 100 Ω resistors in series used to simulate load
Next Step 1/3 4: 1 balun 2/3 coax 1: 1 line isolator Yaesu 897 D
Sources � “Baluns: What They Do And How They Do It”, Roy Lewallen W 7 EL, ARRL Antenna Compendium, Vol. 1. � “Transmission Line Transformers Handbook”, Jerry Sevick W 2 FMI. � “The ARRL Antenna Book For Radio Communications”, 22 d Edition, ARRL. � “The ARRL Handbook For Radio Communications”, 88 th Edition, ARRL. � “More On The 1: 1 Balun”, Jerry Sevick W 2 FMI, CQ, April 1994 � Amidon Associates, http: //www. amidoncorp. com � Palomar Engineering, http: //www. palomar-engineers. com
Questions?
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