3 ms·
FM has a property known as "capture effect". The result is that the stronger station will usually "capture" the PLL (back when they used PLLs instead of SDRs f
by anonymousiam 6y ago
FM has a property known as "capture effect". The result is that the stronger station will usually "capture" the PLL (back when they used PLLs instead of SDRs for FM demod) and you will not hear the adjacent station. It can become a problem in a mobile environment (car stereo) when the signal levels are constantly changing, but "bleeding" is a problem usually associated with other modulation types (typically AM and SSB).
- tzs 6y agoSupposedly this is one of the reasons aircraft radios are AM instead of FM. If two stations transmit at the same time, you want to recipients to hear the interference so they can ask for a retransmission instead of one hearing a clear message and the other having no idea that someone tried to transmit to them.
- Johnythree 6y agoThis. Plus the fact that AM is actually capable of better sensitivity than FM, especially in the narrow bandwidths necessary for aircraft VHF communications.
- Johnythree 6y agoCapture effect has nothing to do with the operation of PLL's. Most FM radios have a Limiter stage which strips of all Amplitude variations. This means that any strong signal in the passband will completely suppress a weaker signal. https://en.wikipedia.org/wiki/Capture_effect https://en.wikipedia.org/wiki/Capture_effect