Impedance and Return Loss

When you deal with high frequencies, above around 100 MHz, you have entered the zone of the "transmission line." It has to do with the wavelength of the signal, and that is a discussion we'll have in future blogs. But what it means is that the impedance of the cable is now important and you have to match the impedance of the source and destination devices.
This also means that everything in-between must match the impedance chosen and, by "everything," I mean cable, connectors, patch panels, patch cords, adaptors, bulkheads, feedthroughs - everything! It also means that any variation in impedance can affect the signal on the line. This is true for every transmission line, whether we're talking about a 50kW RF signal going up to an antenna or an HD video signal going between boxes. Of course, in these two examples the impedance is different (50 ohms for that high-power line and 75 ohms for that video cable).

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