A new MWA limit on the 21 cm power spectrum at redshifts ?13–17

Observations in the lowest MWA band between $75-100$ MHz have potential to constrain distribution of neutral hydrogen intergalactic medium at redshift $\sim 13-17$. Using 15 hours data, we analyse systematics this such as radio-frequency interference (RFI), ionospheric and wide field effects. By updating position point sources, mitigate direction independent calibration error due offsets. Our strategy is optimized for frequency bands by reducing number dependent calibrators taking into account radio sources within a wider view. We remove data polluted based on RFI occupancy conditions, finally selecting 5.5 cleanest data. these obtain two sigma upper limits 21 cm power spectrum range $0.1\lessapprox k \lessapprox 1 ~\rm ~h~Mpc^{-1}$ $z$=14.2, 15.2 16.5, with limit being $6.3\times 10^6 mK^2$ $\rm k=0.14 \rm $z=15.2$ possibility few \% signal loss calibration.