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What can be the reason of FM radio interference?

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A.Anand Srinivasan

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i hear some kind of noise in my FM radio reception when i stand at certain places in my house
isn't fm supposed to be noise free
what is the reason behind this interference
 

throwaway18

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radio interference

>isn't fm supposed to be noise free

No, FM is better than AM at rejecting interfering signals that are weaker than the desired signal.

If interfering signals are near or larger than the strength of the desired signal then you won't get good reception

>what is the reason behind this interference
We have no idea what noisy electrical equipment you have in your house and how strong the local FM signals are so there is no way we can say.
 

alexx

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Re: radio interference

FM is not noise free, but less sensitive to noise than for example AM. When the signal strength goes under a certain level the noise comes very fast because the FM demodulator has not linear signal-to-noise characteristics.

The reason you hear noise in certain places can be:
1. The signal strength is to low.
2. The signal has multi path propagation (and adds at your antenna out of phase)
3. High noise level (from for example electrical equipment, electronics, computer etc)
 

electronics_kumar

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Re: radio interference

A.Anand Srinivasan said:
i hear some kind of noise in my FM radio reception when i stand at certain places in my house
isn't fm supposed to be noise free
what is the reason behind this interference

two reasons i want to share with you all
1)
if there is another signal having same frequency as that of ur FM signal ,interfernce will happen( both will mingle) a new frequency will be produced whose new frequency will be either sum of two freq or difference of the two...so now two signals whose frequencies does not comes under tuned desired frequency then two newly formed signal will be eliminated ...scoring point....
2)
since all most all noises will affect only amplitude of carriersignal ..since it is FM( frequency of the carrier is the place where our intelligence is placed) it will not be affected by noise...superiority gained....

Because this two strong reasons , i dont know how noise occured in ur FM system..may something is to blamed ..which one....
 

sachinlan

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Re: radio interference

This intereferenc could be because of cordless telephones which work in same band.
 

airman

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Re: radio interference

I think "throwaway18" and "alexx" are the correct opinion , because thir perviouse reasons stated , also I want to add a note....

I know surelly that any object isn't at the zero Kelven temp. should produce a thermal noise ( WHITE noise) which contains all the bands of freq. , then these noise to be received by the antenna, which produce a noise. That in addition to the effect of multipath, the objects around you and your radio antenna it sometimes not a wire antenna (omnidirectional) but may be loop antenna (in some what directive).:D
 

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