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We’ve seen several Facebook posts lately about 60GHz and rain attenuation.  There’s a lot of anecdotal comments on how much rain can a link take, as well as when it will or will not go down.  We thought we would share the way that we look at this, as well as some examples, in order to help others.

If you have ever used a weather radar site or app, you’ll have noticed that when there is rain, it is categorized into different colors that represent intensity.  

Here’s an example from Weather Underground:

Notice at the bottom there is a key that converts the colors into dBZ.  These dBZ values can then be converted to the actual rain rate with a formula.  For example:

The next step is to convert this to an attenuation value for a 60 GHz link.  And look at that, the Tachyon Link Calculator happens to have a converter for that!  

Let's look at an example for the Yellow case:

This means that if you have a 1 km link on channel 6, then Yellow intensity rain across the link path would result in around a 4 dB reduction in signal.

On the other hand, if the rainfall intensity is Red across the path, the attenuation is much higher:

The Tachyon Link Calculator also allows the reverse calculation so that you can easily calculate how intense of a rain a link can handle.  In this example, we use a 500 m link with a link budget of 12 dB:

As you can see, this link can withstand a very heavy rain across the entire link path before the signal is depleted enough for the link to drop.  

One note, not all manufacturers provide the receive sensitivity per channel.  In that case, you can use around a -72 dBm as an estimate for calculating the link budget (RSSI - RX sensitivity) for a 2GHz channel in the 60GHz band.

We hope this is helpful to some that are wondering how to equate rain intensity shown on a radar map to what this means for link attenuation!