Transmitting an RF signal

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there is this thing that ses that:

if you have an antenna of length equal to 1/4 of the wavelength of the EM frequency you are trying to transmit, then the antenna will efectivlt transmit the signal.

now does that mean that by following this simple rule you can transmit any frequency you want?

when you are trying to do this practicaly, does the signal going to the antenna have to be a fairly high voltage or something?

and also when the transmitter is conected and working, what kind of load impendance is the transmitter looking at (the impendance of the antena operating as a load)?

 

[throwaway18]

A λ/4 antenna requires a groundplane or counterpoise for a good impedance match to 50 or 75ohms.

does that mean that by following this simple rule you can transmit any frequency you want?

Within practical limits. At frequencys of a few megahertz and below a λ/4 is far bigger than you can practically errect. At high frequencys, roughly10GHz and higher quarter wave elements become very small.

There are also legal restrictions on what frequencys you can transmitt.

does the signal going to the antenna have to be a fairly high voltage or something?

There is no lower cut-off voltage. A small voltage causes a small amount of power to be radiated.

Antennas are typically designed to appear as a 50 or 75ohm resistive load to the transmitter at the frequency of operation.