The UnTenna

This review examines a DIY experimental multiband end-fed antenna designed specifically for portable QRP operations with an IC-703 transceiver. The builder's goal was to create a simple wire antenna that seamlessly interfaces with the radio's internal autotuner to achieve broad multi-band coverage.

The project involved moderate initial difficulty and trial and error. Early experiments using random wire lengths, standard 1:1 or 4:1 baluns, and an FT114-43 core resulted in poor matching and core saturation at just 10 watts. However, the breakthrough occurred when the creator built a custom Unun using a T130-2 powdered iron core. By winding 18 bifilar turns of #20 insulated wire and housing the assembly in a repurposed mint tin, the design became highly effective.

The field results are outstanding. Deployed as a sloper with a 23-foot wire and counterpoise, the system achieves an instant match from 10 to 40 meters, yielding impressive 55 and 57 signal reports on 10W. Upgrading to a 50-foot wire and counterpoise in an inverted L configuration successfully extends tuning capabilities across all bands from 10 through 80 meters. A highly recommended DIY solution.