[ICOM] Using RF Gain

[John]

Here is a question which I should know the answer to, but can't come up with it at the present time.  I have an Icom 706 original, which I generally run with the preamp on.  This makes HF kind of noisy, but turning off the preamp makes the radio pretty deaf (QST measured the MDS at -123dbm, 20 meters, preamp off).  Can I use the RF gain to reduce sensitivity a bit to quiet things up?  A MDS of -130 or so would probably be fine, but there is no way to achieve this by using the preamp and/or ATT.  Can reducing the RF gain lower sensitivity while preserving S/N ratio?

73s John W5TD 

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