S meter noise goes down with ANT preamp increase

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  • Updated 9 months ago
I’m trying to understand why my 6700 S-meter noise readings go down from let’s say S3 with ANT preamp set to 0 dB and then reads S1 or S0 with ANT preamp set to 20 dB.

I’m assuming it’s resulting in an improved signal to noise ratio for some reason but it’s counterintuitive.
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Rick - W5FCX

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Posted 9 months ago

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Ken - NM9P, Elmer

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Essentially Yes.  ... at least until you get to the point that the internal receiver/preamp noise is lower than the antenna/band noise.  Then any additional preamp gain will not be productive.  You can tell by two means:

1) if your background noise on a band rises when you connect the antenna, then you don't need any more gain.

or

2) if your noise floor doesn't go down a little when you bump the preamp gain another notch, then you don't need the additional gain.

Having too much preamp gain gets you nothing except reduced dynamic range.

I don't need any except for 10 dB on 10 meters, and 20 dB on 6 meters.  Sometimes, on a really quiet 12 Meters, I may add 10 dB.  and if I am using a low gain receive loop on 80/160, then I may add some more gain to raise signal levels.

Ken - NM9P
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Bill W2PKY

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Believe Flex said if you observe 10 dbm of additional noise when attaching the antenna then no more pre-amplification is necessary. 
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Ken - NM9P, Elmer

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I believe you are correct, I was just trying to simplify my answer.
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HCampbell WB4IVF

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Craig Williams

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