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Abstract This paper presents a novel design of rigid coaxial line based variable stub tuner. It incorporates controlled drive for the movement of shorting ring along the length of the stub inside the coaxial line. The ring is housed inside stub through linear slot over the coaxial conductor. Inbuilt slot at outer conductor of coaxial line introduces undesirable discontinuity which deteriorates the performance of the stub. It needs to be compensated to?get the desirable performance of tuner. The effect of discontinuity has been analyzed using circuit modelling and compensated in design itself for the desired performance. The compensated tuner has been fabricated and tested where test results are found as return loss better than 25?dB and Voltage Standing Wave Ratio （VSWR） in?between 1.1 and 1.9 in the frequency range of 80–850?MHz. The presented work is useful for the development of high power stub tuner in the range of High Frequency （HF）, Very High Frequency （VHF） and Ultra High Frequency （UHF） which is an interest of wide spread applications in areas of communication, defence, satellite, radar, tokamak etc.
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