I heard that antenna convert the electrical signal to an electromagnetic signal.


what is the range range of electromagnetic signals?

 

I heard that antenna convert the electrical signal to an electromagnetic signal.


what is the range range of electromagnetic signals?

Radio telescopes pick up radio waves emitted from distant galaxies - that's a reasonable range.

Closer to home - Some of NASA's deep space probes have been sending signals from the edge of the solar system.

Even closer to home - short wave radio signals can readily propagate around the Earth.

 

I think the OP is talking about frequency range.

There really aren't any limits in size. A full wave dipole for 1Mhz is several miles, while light (which is increadibly short) would require nanotech lengths. The thing is, for those lengths (think upper microwaves) that are mechanically practical you can tweak the antenna electronically with capacitive or inductive reactances, and make its length seem different than it is.

You want some really long wavelengths either google or look up ELF with Wikipedia.