3 ms·
An antenna doesn't amplify a received signal. It takes an actual electrical amplifier to do that. When an antenna's gain is being mentioned, that gain is actual
by sizzzzlerz 7y ago
An antenna doesn't amplify a received signal. It takes an actual electrical amplifier to do that. When an antenna's gain is being mentioned, that gain is actually how much better the antenna is at taking in more of the signal than the standard candle isotropic antenna, e.g., one that transmits and receives equally in any direction.
- spapas82 7y agoYes I tried to make that clear by mentioning that an antenna is a passive device. I just wanted to clarify that antennas help both at the transmitting and receving end. English are my 2nd language so maybe I could have explained it better...
- madengr 7y agoWell it amplifies the signal by the Q of the antenna. The issue is that high Q resonators make lousy radiators, as the radiation resistance is very low compared to the reactance, and bandwidth is 1/Q. But you can certainly get amplification by a high-Q resonator inserted in a field. This is why electrically small antennas have an effective aperature much, much larger than their physical size. That ferrite rod antenna in an AM radio can have a massive electrical aperature (antenna gain) since it is narrow band (high Q). The resonance is amplifying the signal. You can also transmit through it if you can keep it cool. It may have 0.1% efficiency, radiating 1W for 1 kW of input power, if you have a nuclear reactor (say a VLF antenna on an aircraft carrier where you can’t have wire antennas), you can trade power for size.