The Marchand balun is not square

Marchand balun image from original published article.

Marchand balun image from original published article.

I recently had the privilege of seeing the inside of a real vintage Marchand Balun. One of the Professors at Stellenbosch University lent one to us that he built in the 70s so we could see how it looks (from the outside). Even seeing just the outside was quite informative as all Marchant balun sketches found in papers and text books makes it seem like these baluns are square (as shown in the image above, taken from the original paper “N. Marchand, Transmission-line conversion transformers, Electronics, vol. 17, December 1944, pp. 142-145. (Reprinted in J.L.B. Walker et al.”) but they’re not. They’re rectangular like the one shown in the image below.

Like with most engineers, curiosity often overrides the desire for preservation. So while I was busy writing this blog entry, a couple of the engineers in the office unsoldered, cut off the semi rigid and opened up the cavity to have a look inside. These baluns are actually quite impressive as they have very wide operation bands from 2:1 up to 10:1.

Real life Marchand balun

Real life Marchand balun

Author: Robert Kellerman

One Response to “The Marchand balun is not square”

  1. akhil says:

    will you please send me the design steps for the balun of having 1:10

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