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I have an argument with my friend about drone radio systems. My assumption is this: the bigger the receiver the better reception is possible to achieve. The logic behind this is geometry: transmitter emits an electro-magnetic wave of some shape and a front of this ware gets expanded away from the transmitter fading gradually. The further away from the transmitter - the smaller the amplitude of the wave and as the result - energy. If I stand at some distance from the transmitter with the receiver, it gets information from the wave's energy. So the bigger intersection of the receiver with the front of the wave - the more photons it can capture, therefore, theoretically, useful information.

My friend disagrees and had a very different option. The only configuration of the receiver that matters. If you have 10 times bigger receiver you'll inevitably get x10 noise level so no theoretical improvement is possible due to however big your receiver is.

I'm sorry in advance if it's a too basic question, from a drone hobbyist perspective antennas physics is dark sorcery. So ELI5 answers are appreciated.

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It depends on the frequency whether you are right or your friend is. It is true that the noise power is additive but so is coherent amplitude and that is what you get when you add up properly in phase the amplitudes. Then only the total capture size matters. The total receiver noise against which you detect the signal is more complicated because it comes from at least two sources and by far the most significant are the outside atmospheric and/or jamming noise and the other is locally generated in the receiver by the front-end amplifier. Below 10MHz the atmospheric noise dominates, while above 1GHz the local front-end amplifier.

So a commercial AM radio operating below 1.5MHz can get away with a tiny antenna followed by a simple detector diode without a preamp because its SNR depends only on the received noise. This is very different for a satellite receiver operating in essentially pure internally additive noise environment, so bigger the antenna is the better the reception you get.

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  • $\begingroup$ thanks a lot! With drones with speak mostly about 1 GHz+. I'm not sure whether any drone equipment uses AM, but we speak about theory. So, basically with 1GHz+ bigger receiver antenna can theoretically works better, correct? $\endgroup$
    – lebed2045
    Jul 31, 2021 at 10:03
  • $\begingroup$ yes, above 1GHz the bigger antenna wins. Usually the beamwidth being inversely proportional to the aperture size is the technical one placing a limit as to how large the antenna can be. The narrower the beam is the more difficult/complicated will be the tracking mechanism, eventually the beam can be so narrow that the tracking error places a lower limit on SNR performance. $\endgroup$
    – hyportnex
    Jul 31, 2021 at 18:16

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