4:1 Current ('Guanella') Balun - Made Simple.

I was never an electronics whizz.  That often means I need others to show me how to make things.  I like making things.  It saves me lots of money and I develop a sense of understanding for the components.

It's thus a great shame that so few people who claim to be experts volunteer clear guidance on making things.

Thus, it gives me great pleasure to reproduce EA6XD's wonderfully simple and helpful diagram on making a 4:1 current (as opposed to voltage) balun.  All you need are some ferrite cores, some wire and connectors.

A current balun is widely held to be better than a voltage balun as it forces equal currents in the two halves of the antenna.  Forcing equal voltages with a voltage balun does not, apparently, force equal currents.

In building a windom such as in this example, it's much easier to have the balun at ground level than weighing down the centre of a dipole, unless you are using a tree or equally sturdy support.  If you want to use it on some bands, it needs a 1:1 and not 4:1 balun, so having it in a tree is a bit inconvenient!  In that configuration, you feed the balun with a short length of coax to the ATU/transceiver - it can be in the shack or just outside - and then some twin to the dipole centre.  A useful starting point for lengths etc can be found here.

If you take your time, you'll have the satisfaction of beraking free from expensive, commercial baluns that are sometimes of a criminally poor quality, and rarely of a current type.  Total cost of these units, including an IP65-rated enclosure (E-bay usually provides!), comes in at about £8 or so.  You can drill a hole for the SO-239 socket using a normal drill or a blowtorch-heated piece of 22mm copper pipe.  I prefer the hot pipe because it produces a clean hole; drill bits tend to 'catch' the plastic and make an irregular hole.

One final piece of advice: once you've put this in a watertight enclosure, make sure you drill a small vent hole where any water getting in can drain away and the unit then dry out.  I found that water slowly gets blown in via the tight but unsealed coax socket (this is a very windy area) so you need to add a gasket of silicone or similar to stop this.  Alternatively, you can pop the balun under an upturned flower pot or something!