MATCHING BALANCED-LINE FED ANTENNAS

An Analytical Investigation to Determine if the 80+ Year-Old "BELIEF" that a Balanced Antenna Tuner is the Best Way to Match an Antenna Fed with Balanced-Line Feedline.    (e.g., "Ladder-Line, "Window-Line", "Twinlead")


Is this Fact?  Myth?  Wishful Thinking?

Note: Before we begin, let's agree to use the short term "ATU" (Antenna Tuning Unit) to represent to whatever you prefer to call it:  "Antenna Tuner", "Antenna Matchbox", "Antenna System Matchbox", "Antenna Coupler", "Whatever".

CONTENTS: 


  • About this Research (this page)
  • Basics Definitions:
  • What is a "Balanced-Antenna"?
  • What is "Balanced Feedline"?
  • What is a "Balanced ATU"
  • What is an "Unbalanced ATU"
  • Components
  • How I Measured
  • Measured Results
  • Comparisons
  • Discussion and Conclusions


About this Research:

For decades now, many Hams have insisted that the best way to match an antenna fed with balanced-line feedline is with a "Balanced ATU".


  • Many hams (especially stateside hams) insist that the old "Johnson Viking Matchbox" is by far the best solution.  IMO they see it as a long lost dream.


  • While many European hams insist that the "ANNECKE" (symmetrical) ATU is the very best.



Vs.



In the past 25+ years, many other hams, including some of the hobby's top Gurus (e.g., VK1OD, W8JI) have suggested that an "Unbalanced ATU with a good external 1:1 Guanella (Current) Balun" works just as well. 

And is cheaper and easier to find on the used market.


The "opinions" in both camps are well represented, but "opinions" prove NOTHING!


Fundamentally, the goodness of the match is determined by three factors:

  1. The Amount of RF current transferred from the TX to the Feedline.  (More is better.)
  2. The Balance of RF Current on each line of the feedline.  (Should be equal - rarely is.)
  3. The Phase of the RF Current on the feedline.  (Should be 180 deg. out of phase.)


ALL three of these are  measurable, so there is really no need for a debate on this topic!

  • Measuring the 'amount' and 'balance' of the RF Current is quite simple,
  • but measuring the 'phase' is a bit more difficult.

In my comparisons, I will show measured results for the amount and balance. 

I will also show a link to Tom Rauch's (W8JI) test where he shows phase as well comparing the two ATU's shown above on this page.