If wavelength is 2 meters, antanna is .50 meter how many percent of power are transmited?
Answer:
You've provided no antenna design information, so we'll assume you've got yourself a dipole to play with.
You have created a 1/4 wave dipole with, apart from any feed losses (at 73 ohms) or other losses, produces a gain of 1.86db. So your EFFECTIVE power aimed directly 90 degrees broadside to that antenna (that's the strongest direction in the radiation pattern for a dipole) would be about 1.5X the power you put in.
However, it is unlikely that your transmitter and coax expect to operate at 73 ohms. You'd do OK with 75 ohm coax as long as the transmitter was willing to do so (they're more typically set up for 50 ohms). You'd need some sort of transmatch to get the gain I provided above.
Other antenna designs, especially multi-element, can have gains considerably higher than I showed for a simple 1/4 dipole.
if you have a swr of 1.1 100%
depends on the antenna design..there are many types.
strange question. are you talking the ratio of TPO (transmitter power output) to ERP (effective radiated power compared to reference dipole)? All of the TPO gets radiated no matter what the size of the antenna elements except for a small amount that gets converted to heat. The antenna "resistance" is a fiction used to calculated feed requirements, but that is radiated, not converted to heat as an actual resistor would do. The radiation may not go in the intended directions so that may reduce the quality of the antenna system. the manufacturer's ERP calculations are usually based on radiation in a prefered direction and disregards spurious. So the antenna ERP can be and often is greater than TPO, it is not a percent efficiency thing.
antennas that are very short compared to the operating frequency, such as an HF whip antenna on a car have resistance loss that is comparable to the radiation resistance. that could be called an efficiency factor because it will generate heat as RF is applied and that reduces the RF available for radiation. The antenna you propose is not so short that it should be a factor, in fact if used with a proper ground plane it should be a quite efficient radiator.
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