Needle-like properties of the probing RF field of "magnetic-field” probes based on the single-layer flat coils

A single-layer flat-coil-oscillator activated by a low power backward tunnel diode has been elaborated and created. As an inductance in a pick-up circuit of the oscillator, such a flat coil served as a "magnetic-field” probe in such a measuring instrument. The created oscillator was activated both without and with an external capacitance C0 in its resonant circuit, i.e. the flat-coil oscillator might be also activated with its own (internal) capacitance $C_c$. Investigation of "probe-formative” capabilities of this research instrument with such an unusual coil (versus $C_0$) showed that with a reduction of the value of this capacitance the feeling (probing) field of such a probe exponentially becomes longer, i.e. these probes become more far-ranging with decreasing $C_0$. The revealed property of "magnetic-field” probes would permit an essential widening of capabilities of flat-coil-based probe microscopes. It may also permit to enhance the efficiency of searching and detection of the nodal structure, arising at an unusual phase transition from the "uniform” to “non-uniform” superconductivity, predicted independently by Fulde and Ferrell, and Larkin and Ovchinnikov.