1:why is there no phase modulated radio stations?

Answer 1

Because PM offers no real advantages over FM and both the transmitters and receivers are considerably more expensive to build.

But there actually *is* one application of PM in commercial broadcasting. The 3.58 MHz chroma sub-carrier in commercial color television broadcasting uses PM to encode the chroma information for the picture.


Doug

Answer 2

If there are, or are not phase mod stations, depends on who you ask, and exactly what you ask. See FM, frequency modulation, and PM, phase modulation, are so similar that they can both be received by the same receiver. In practice, PM has more energy in the higher frequencies. The text books will be very clear on the different definitions, but in practice one can be converted to the other with a filter called "pre-emphasis" or "de-emphasis" which is about 6 db starting at 2.1 kHz. In fact, all "FM" broadcast transmitters use FM modulators, but the audio has been "preemphasized" with a 75 microsecond filter, making the resulting signal exactly the same as what would have come from a PM transmitter. To get the audio back to normal, all receivers have a 75 us "deemphasis" filter.
So if you look at the actual signals, all FM radio stations are phase modulated

Answer 3

The equipment required to receive a phase modulated signal is a little more complex than the equipment required to receive FM or AM.

There are also issues with ambiguity of the signal- it is difficult to decode 0 degrees of phase or 180 degrees, for example.