Abstract: A precision marginal oscillator-type nuclear quadrupole resonance (NQR) spectrometer using field effect transistors (JFET'S) is described in this paper. The frequency is succesivcly adjustable by several ranges from 14 MHz to 35 MHz, This spectrometer shows a high sensitivity and small wave shape distortion. At room temperature, the measuring accuracy of NQR frequency of ³⁵Cl in polycrystallinc powder of potassium chlorate sample is about 3×10^-6, the signal to noise ratio (S/N) of NQR spectrum of ³⁵Cl in recrystallized sample is greater Than 150. The obtained chlorine's quadrupolc coupling ratio (eQq) ³⁵Cl/(eQq) ³⁷Cl in potassium chlorate, sodium chlorate and sodium chloride art 1.2687363, 1.2687306 and 1.2687661 respectively. The relation of nuclear quadrupole resonance frequency and temperature have been studied by ³⁵Cl in polycrystalline powder sample when the temperature was varied from 77 K to 393 K.

Key words: NQR, Spectrometer, Marginal oscillator,Probe, Sensitivity, Solid state