In that case you'd need a tuned cavity bandpass/notch filter. That is, one which will only pass that very specific frequency and reject all others. Such devices are not inexpensive! 
(Cheap) Ebay Filter?
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sorry I mean: 446.000 - 446.200
here its 430 - 439.400
All Toy Radios use that freq.
So you're not getting unintentional interference from another frequency, you're getting it on the same frequencies from other devices that use those same frequencies?
Delta33
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. You're Not saying enough to make yourself Understood. BE more specific.
I dont know where the noise come frome. I see it in my SDR.
Then you're wasting everyone's time.
If the noise is other transmitters on the same frequency, a filter WILL NOT HELP. The only thing that might help is a directional antenna, if you can point it at the transmitter you want to hear, and away from the one you do not want to hear. If the transmitter you want to hear is north, and the noise is east, the directional antenna will help. But if they are both north, it will not help.
If the noise is bleed-over from a strong signal on some other frequency, YOU MUST KNOW THE OTHER FREQUENCY to get the right filter to get rid of the noise, unless you get a duplexer-style cavity bandpass filter that only passes a single frequency and blocks everything else. But those filters are large, expensive, and require professional test equipment to tune properly. And you'd have to have them retuned (or buy another one) every time you want to listen to an additional frequency.
If the noise is other transmitters on the same frequency, a filter WILL NOT HELP. The only thing that might help is a directional antenna, if you can point it at the transmitter you want to hear, and away from the one you do not want to hear. If the transmitter you want to hear is north, and the noise is east, the directional antenna will help. But if they are both north, it will not help.
If the noise is bleed-over from a strong signal on some other frequency, YOU MUST KNOW THE OTHER FREQUENCY to get the right filter to get rid of the noise, unless you get a duplexer-style cavity bandpass filter that only passes a single frequency and blocks everything else. But those filters are large, expensive, and require professional test equipment to tune properly. And you'd have to have them retuned (or buy another one) every time you want to listen to an additional frequency.
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