Just don't make the common mistake of thinking that the units on your
receiver's S meter are 6 dB. That can lead to some extremely mistaken
conclusions.

Hams keep insisting that an "S-unit" is 6 dB, while the marks on typical
S-meters almost never are, and sometimes are much different ( 2 dB for
example).

Roy Lewallen, W7EL

Caveat Lector wrote:

Agree and disagree

For example, let's start with a 100-Watt exciter then add an afterburner of
800 Watts. Doubling power is 3 dB and an S-unit is 6dB. So from 100W to 200W
is 3dB, 200W to 400W is 3 more dB, and 400W to 800W is 3 more dB for a total
of 9 dB or only 1-1/2 S-Units possible increase on the receiving end. One
can achieve almost the same result with a 3-element beam.

BUT Although one and a half S-Units does give a little more oomph while
working a pileup, it really comes into play for weak signal work where if it
gets you just up out of the noise on the receiving end, two way QSO's may be
possible where without the linear, the DX just can't copy. I can attest to
this many times on any band.



On the other hand I have worked DXCC - QRP - 5 Watts



A lot depends on propagation (of course)