The high frequency magnetic field of a flat spiral coil, with an inner opening about one‐fourth the diameter of the coil, was excited by single‐tube tuned plate‐tuned grid and push‐pull oscillators. Frequency range 1500 to 6000 kc/sec. The magnetic fields thus excited were compared with the fields produced by a direct current. The results when a push‐pull oscillator was used to excite the high frequency field showed no apparent difference, except near the far edges lying about 25 cm from the center of the coil, and were independent of frequency.Unbalanced high frequency excitation showed magnetic field crowded toward the normal axis when filament lead was connected to inner turn of spiral. Field strength across inner diameter was found to be non‐uniform when field was excited by a balanced push‐pull oscillator. Field strength along normal axis of coil diminished more rapidly for a balanced than for unbalanced excitation, independent of method of lead connections and was much smaller for the case of filament lead connected to outer end of spiral.