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

A new MWA limit on the 21 cm Power Spectrum at Redshifts $\sim$ 13 $-$ 17