Theshield should be totally separated at this point.This style ofshielded coupling loop will make the entire antenna systemunresponsive to electric fields. At the top of this coax loop, cut theshield and produce a small gap all the way around the coax. Where the loose endmeets the coax again, strip and solder both conductors of the looseend to the shield of the coax. RF probe measurementshave indicated no common mode currents on the feed line in bothcases and the antenna patterns are well defined in both cases sobalance does not seem to be problem.To create a shielded couplingloop simply take the end of the feed line coax and loop it back uponitself to form the desired loop dimensions. This is to keep the resistive losses low.The conductordoes not have to be solid. Choose a conductor with aslarge diameter as you can find and it preferably should be copper(or silver). The larger the loopdiameter, the greater the efficiency.If it is made larger thenabout 1/10 wavelength in circumference it will no longer beclassified a small loop and its radiation pattern will begin tochange. Choose the desired loop diameter based uponmaterials available and performance desired. Loops at the upper frequencies may still be useful forreceive only applications such as radio direction finding or use asa front-end bandpass filter.Diagram of a Small Loop AntennaEquivalent CircuitMagnetic Loop Antenna PatternConstruction of a small loop is pretty straightforward. The loops I have built for higher frequencies exhibitthe useful sharp nulls and very narrow bandwidth but even for verythick conductors the loss due to the skin effect is just too highfor transmitting applications.The UHF loopdescribed later this page is very small and was made as efficient aspossible without resorting to silver plating or superconductingconstruction yet it still gets very hot with only 10 watts of RF at445 MHz.

Rg58 magnetic loop