In addition to the maximum span needed for short distance resolution in TDR mode, some industries, i.e. the cable television industry, utilize wide bandwidth filters, band stop, and high/low pass filters throughout the range of 50-1000MHz are common. A typical example of these would be high and low pass filters separating large spectral chunks of this range for specific purposes. Filters that are several hundred MHz wide. Reasonable filter response flatness < =/- 1dB or so, is critical to transmission of wideband digital QAM carriers to insure reliability.
