If I have 7 dB of loss in my antenna cable does it actually affect range since any noise is attenuated the same amount as the desired signal? Open


This is one of those Zen "It depends" questions and answers. If you are in a high noise environment you will attenuate the signal and the noise the same amount and the signal to noise ratio at the input to the receiver will remain about the same. The performance of the system in the high noise environment will not change due to the 7 dB of attenuation.

If you are in a quiet environment, (the middle of Montana) then you will attenuate noise and signal the same 7 dB. The external noise is now attenuated to a lower value than the front end noise of the receiver. The front end noise of the receiver is now the determining noise floor and you've reduced the signal 7 dB so you get 7 dB less range than you would have gotten in the wilds of Montana.

Since RF is hard to see directly (magic), let's put it into audio terms that is maybe more familiar. If you have a good mic in a very noisy environment and the talent is screaming into it (rock venue), you can attenuate the mic signal 7 dB (pad), then turn up the gain 7 dB to compensate and the system signal to noise ratio will remain the same. 

If you insert the same 7 dB attenuation pad in the mic line while recording a very weak signal in a quiet room (one hand clapping in a Zen temple) then the input noise of the mic pre amp is the dominant noise source and the overall signal to noise ratio is decreased 7 dB as you have turn up the board gain to compensate for the 7 dB mic pad. The pre amp hiss is now the problem.

So as I said, it depends. In general it's not good to throw away 7 dB of signal from the antenna, but sometimes it doesn't hurt.

Posted 3 years agoby LectroAdmin

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