TopBand: Rx noise figure

[Larry Higgins]

Something I've wondered about for some time: if daytime 160 beverages
require only an amp having a 5 db noise figure or better, and nighttime 20
db or better, why do we need preamps at all?  I would have thought that
even the worst receiver out there would do better than a 5 db noise figure,
let alone 20 db.  

On the other hand, since virtually everyone either uses a preamp or says
they are necessary, there must be a reason.  I see some other postings
which say that receiver noise figures really aren't that good.  Are they
really that bad?

Larry, N9DX

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