WordNet records no synonym and no antonym for astatic coils. It is the only member of its synset, which is common for technical, taxonomic and single-sense vocabulary — there is no other English word that means the same thing. The broader and narrower terms below are the useful relations in that case.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
an arrangement of coils used in sensitive electrical instruments; the coils are arranged to give zero resultant external magnetic field when a current passes through them and to have zero electromotive force induced in them by an external magnetic field
Synonyms, antonyms and the broader and narrower relations for astatic coils come from Princeton University’s WordNet. Full sources and licences.