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Is it to do with how many photons can be absorbed in a given area? more surfaces mean more photons are absorbed but does it translate to better quality? btw can a single atom be as good as the largest satellite dish in term of quality?

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Communications satellites beam a directional signal to the Earth as shown in the diagram below with the area over which the satellite signal can be received called the "footprint".

enter image description here

The signal from the satellite from the satellite becomes weaker nearer the edge of the footprint and in regions where the signal is weaker a larger diameter satellite dish needs to be used.

Here is the "official" footprint of the Astra 2D satellite with the larger number (the recommended diameter of the dish in centimetres) indicating a weaker signal.

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This map below gives the estimated dish sizes needed for reception in Spain where the locations are outside the "official" reception areas.

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So if you need a certain number of photons per second to produce a decent tv picture and the rate at which they arrive per unit area is small you will need a larger area (bigger dish) to collect the requisite number of photons per second.

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