why does the FM radio signal go fuzzy when somebody walks into my garage?

Question

every time somebody is in the garage the radio signal in the get completely fuzzy...they can be anywhere in the garage too, its not just in a certain spot...its really wierd and i was just wondering if anyone knew.

Answer 1

The same way that a security light switches on when somebody gets close enough to it. Those lights have a capacitance switch in them..

The local capacitance changes when people are in the garage and that affects the operation of the aerial tuning circuit, producing white noise.

Inductance/capacitance tuning is the usual means for FM radios although it's normally via a fixed inductance and a variable capacitor which is what you turn when you tune the radio.

Common problem type....osc is an oscillator

https://answersrip.com/question/index?qid=20091030154556AAQwZFk . . . .

Oscillators detect FM signals and a changing capacitance sends it all over the place, producing a lot of frequencies which together produce a sound known as white noise. You can get the same by moving a coaxial aerial lead connected to a Hifi FM tuner In some places a white noise is produced and in others the signal is good.

http://www.somerset.net/arm/fm_only_lowtech.html . . . . .

There will be plenty of reflected signals in the garage so the line of sight effect will not be the prime culprit although it does have an effect.

Very good FM hifi tuners have a reflected path (delayed signal)/direct path (normal signal) analyser and allow the reflected signals to be filtered out.

It's an old radio joke that very large people have a better capacity for messing up radio signals.

Answer 2

This is an example of a weak signal being distorted by something called "Standing Waves", where the body of a person in the garage reflects enough signal that the receiver is getting about as strong a signal via the reflection as direct from the transmitter. This is called "Multipath", and is often seen in FM with weak signals. In the old analog TV system, it would show up as ghosts. Try moving the receiving antenna to a different location, perhaps near a window.

Answer 3

The antenna for the radio must be just something connected directly to the terminals on the radio, not on the roof. That means if someone walks between the antenna and the station, their conducting body partially blocks the signal. FM transmission is very line of sight.



Just like if you are looking at something distant with a telescope and someone walked in front of the scope.



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Answer 4

because you now have two conductors instead of one and the band gets confused.