An example system comprises a first antenna and a modem. The first antenna is configured to receive a signal from a transmitting radio frequency unit. The signal includes data and a known sequence. The modem is configured to retrieve the known sequence from the signal, transform the known sequence and the data into a frequency domain, calculate averages of groups of neighboring frequency points in the frequency domain to reduce the effect of nonlinear noise in the signal, the neighboring frequency points corresponding to the preamble in the frequency domain, compare the calculated averages to an expected frequency response in the frequency domain, determine a correction filter to apply to the data based on the comparison, apply the correction filter on the data in the frequency domain to create corrected data, transform the corrected data from the frequency domain to the time domain, and provide the data.
