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Friday, 24 May 2013

Really, More Baluns - Now What?


You may recall my musings on the topic of Baluns back here:

A Balun is a kind of transformer to take a BALanced signal and convert it to an UNbalanced signal (or vice verse).

So, in my traditional have a bash style, I've made this:

Now, the schematic of the thing looks like this:

Now, the B2/C1 junction is ground and C2 and A2/B1 are the balanced outputs. The unbalanced port is between the same ground point (B2/C1) and A1 for a 1:1 and A2/B1 for a 4:1.

So here I am injecting a 4MHz signal into the 1:1 unbalanced port and monitoring the two balanced outputs with the 'scope:

This looks exactly as expected - the purple line is the sum of the two balanced outputs and for two signals perfectly out of phase should be a flat line. Here is the same thing at 7MHz:

Again - nothing short of perfection!

Here at 14 MHz:

the signals are still out of phase with each other, but the amplitudes of the two balanced ports is no longer equal, and here at 18MHz:

The two ports are no longer anything like out of phase....

So this homebrew device looks like it's good to about 10MHz and not much further. Its been made using FT240-61 ferrite material.

I need to now make something similar using a different material and see what the difference is.

Interesting though, hug?

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