Why is the 60 GHz Band not good for long-range communications?

At 60 GHz, Oxygen molecules in the atmosphere interact with the RF signals to cause significant attenuation. Due to this attenuation the 60 GHz band is not a good frequency to use for long-range radar or communication applications. At 60 GHz O2 can cause an attenuation of up to 10 dB/km.

As we go higher up in frequency gasses in the atmosphere start to react with RF Signals causing attenuation. As seem in the diagram below oxygen causes significant attenuation at 60 GHz and water vapor causes similar attenuation at 24 GHz and 184 GHz.

However, this attenuation only really matters in long-range communications, the 60 GHz band can still be used for short-range communications, such as local wireless area networks. The 60 GHz band can also be used for communication between satellites (called cross-linking) in the high earth orbit. Since there is almost no oxygen in space at the geosynchronous altitudes of 43,000 km or 26,000 miles, attenuation at this frequency is minimal.