Eastern Arc vs Western Arc

regarding reception and arc.

It is more a function of where you are located rather where the satellite is located.

The western US generally has dry, clear skies and the signal is not degraded as much by the air having higher water content.
The eastern US and particularly the southeast, has higher humidity (water vapor) which degrades reception of the signal.

The FCC compensates for the effect by allowing higher transmitter power levels for the eastern part of the country.

When all of it is put together, there is not much difference between the two arcs for most customers.
 
There are multiple extensive FCC regulations on satellite interference and ground reception.
This map provides an idea of how the FCC divided the country when looking at transmission regulations.

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