Let’s pretend you had a transmitter and an antenna. What determines the frequency at which you will broadcast? On one hand, doesn’t the transmitter have an oscillator which determines the Hertz? Yet, the physical dimensions of the antenna will govern whether or not it can send the signal at all, right? So, is that answer that it is a function of BOTH the receiver AND the antenna?
I’m not an engineer or amateur radioist or whatever, but with my limited understanding of physics and electronics, I can say that the primary thing that governs a signal is the oscillator.
The radio as a whole, but primarily the oscillator circuitry determines the output frequency.
The antenna geometry and mounting determine the effectiveness of getting the signal out to far distant lands, or the cell tower.
If I can recall my all-encompassing technical knowledge that earned me an official FCC radiotelephone license (third class) 30-odd years ago, it’s the transmitter. If you’re close enough and the transmitter is powerful enough, you’ll pick up a signal even if no antenna is present.
Weeeeel yes but … Most FM transmitter use a relatively low frequency oscillater followed by frequency multipliers to get up to the final output frequency. This is done because the output frequency needs to be frequency controlled by a crystal or other stable frequency control. At the same time it is desired to have a wide frequency deviation for good noise suppression. That is the carrier frequency needs to vary over a wide frequency range for good results.
Stable frequency control isn’t compatible with wide frequency deviation. So they use a low frequency (or phase) modulated oscillator with a relatively narrow band of frequency modulation. Then the oscillator frequency is multiplied to get the final transmitted frequency and this process also multiplies the frequency deviation by the same amount.
For example suppose you have an 8 mHz oscillator frequency modulated from 7.9 to 8.1 mHz. This is a deviation of 200 kHz. If you multiply it by 10 the deviation is from 79 to 81 mHz which is a deviation of 2 mHz.
The transmitter determines the frequency. The physical dimensions of the antenna determine how efficiently transmitter power is coupled to the outside world. An antenna of the wrong length for a given frequency will still work, it just wont work as well as an antenna of the proper length.
If the antenna isn’t carefully tuned to match the frequency of the transmitter, then aside from just being inefficient, a lot of the energy can end up getting reflected back into the transmitter. Depending on how your transmitter is designed, the excess energy reflected back into it could cause the transmitter to die a very ugly death.
You’re talking about an impedance mismatch between the transmitter and its load (transmission line and antenna). This can be fixed by using an impedance matching network between the transmitter output and the antenna, at the transmitter, at the antenna, or by using the transmission line itself as an impedance matching network,