In the Dutch Newsgroup net on 80 meter there was a discussion about about feed lines. The main issue was, when using open wire, it's important to balance the current through those lines to the actual antenna. Because those currents are balanced there should be a minimum of RF on those lines, and the radiation will be from the antenna itself.
The big question in this discussion was how to measure those currents. After this discussion Gert-Jan van Dam (PA1G) has developed the antenna current meter. I did realize the importance of this issue and made one myself.

Click on photo for bigger one

The schematic is as follows :

As you can see on the second photo above the transformer 1:30 is build in ingeniously. For the one winding a peace of coaxial feeder is being used, on which the braid is used for shielding the internal core from the coax.
As you see this device is simple to build. All parts are from Conrad, except the meters and iron powder core. Those items i bought at the DNAT (Dutch-German Amateur Meeting) in Bad-Bentheim for little money.

Thanks to Gert-Jan (PA1G) for developing this circuit.