(ANTENNA)  BALUNs

       Few Topics are as Confusing and      Misunderstood as the BALUN.

FACT #1:  A BALUN is a Transmission Line Accessory, NOT an Antenna Accessory. 

FACT #2:  BALUNs are described in the Transmission Line Chapter of every ARRL HANDBOOK, NOT in   .                   the Antenna Chapter! 

.                When mentioned in the Antenna chapter, it says "see the TRANSMISSION LINE chapter)".

FACT #3:  THE MAIN PURPOSE of a BALUN is to prevent Common Mode Current from flowing on the              .        Transmission Line, thus maintaining a balance in Differential Current (i.e., equal current but      .              opposite polarity) flowing in each of the two lines of the transmission line.

FACT #4:  TRANSFORMER BALUNS are baluns with a secondary function of transforming the impedance .                to some ratio other than 1:1 (i.e., 4:1, 9:1, etc.).  If the device does not impede the flow of .                Common Mode Current, it is just a transformer, not a BALUN.

FACT #5:  This probably contradicts what you may have heard or thought to know about BALUNs.

Rather than try to convince you in my own words, I will provide LINKs to experts          on this topic and let you choose what you wish to believe after reading them.

The very first thing we must agree before going further is what the task of a BALUN is and how it accomplishes it.  This was best described in a paper by Roy Lewallen (W7EL) - the author of EZNEC Antenna Modelling Software - and published in Volume One of The ARRL ANTENNA COMPENDIUM.

In that paper, Roy coined the terms "Current BALUN" and "Voltage BALUN".  Prior to that they were known as Guanella BALUN and Ruthroff BALUN.

• If you have never read this paper, I STRONGLY SUGGEST you read it now.
• If you have already read this paper, I suggest you re-read it before continuing.
  

LINK:  Baluns: What They Do And How They Do It

NOTE:  Roy gives a presentation on BALUNs every year at the Dayton Hamfest.