Johnson Viking Matchbox vs. Transmatch

The legendary "John Viking Matchbox" was thought to be the ultimate antenna matchbox for matching openwire-fed antennas.  It uses link-coupled coils and differential variable capacitors.

The "Transmatch", originally described by W1ICP, has been simplified in modern times and is now more accurately referred to as a T-Network matchbox.  The Ameritron ATR-30 is a typical example of many similar matchboxes, including the MFJ-989, the Vectronics HFT-1500, and Palstar AT-3K/AT-4K. 

In 2010, Tom Rauch (W8JI) ran a series of lab tests on various baluns, as well as these two antenna matchboxes.  The antenna used was an 80m doublet, about 120 ft. above ground, and fed with Wireman balanced feedline. 

Tom recorded a lot of data on his web site and described his test

"Ladder Line Voltage and Current Test", near the bottom of the page, HERE .

I have extracted a portion of his measured data, specifically the measurements on these two antenna matchboxes and compiled them into the chart below. 

This complements the other 4 Antenna Matchbox Shootouts described in this section of my web site.

The quality and efficiency of the matchbox depends on the amount of RF current it delivers into the balanced feedline, as well as the balance of current fed to each wire.  Ideal is when the current in each line is equal, and as high as possible.

The amount of RF current depends on the amount of RF power applied to the matchbox as well as the impedance of the antenna system at the matchbox.  Therefore, you must only compare RF current measurements of different matchboxes in the same band.

BALUNS:

You will notice that two sets of measurements are shown for the ATR-30 on some of the bands.  Like most asymmetrical antenna matchboxes, the ATR-30 has a built-in balun - that is not very good.  On some bands, Tom also tested using a home-brew external dual-core balun instead of the built-in balun.

On the same page as Tom's test of the two matchboxes, he also made several tests comparing single and dual-core 4:1 current baluns.  The results of these tests show how much better the dual-core balun is than the single core.   It is well worth a read!

CONCLUSION:

The results shown here along with the test results of the other matchbox shootouts in this section of my web, show that in most cases a good asymmetrical matchbox with a good external balun may be used to obtain as good as, or better results matching balanced-line-fed antennas as symmetrical matchboxes.

(DJ0IP)