[TowerTalk] RE: 6db per s-unit?

[L. B. Cebik]

On Sat, 9 Aug 1997, Tom Osborne wrote:
> Roger A. McCarty wrote:
> > he challenged me ie, "Where did you hear that?" I couldn't answer him. 
> > I have maintained as fact 1 S-Unit = 6 DB my entire life, but I cannot
> > find a technical source to confirm. Any help?
> > 
> > Roger KD6CC
> 
> Check April QST
> 
> Tom W7WHY
The proposal for an industry-wide standard of 1 S-unit = 6 dB goes back
into the 40s.  It was never adopted on an industry-wide basis, basically
because it was (and still is) a daunting task to equalize gains in the
amplifier and mixer chain of a receiver to achive this figure.  Ten-Tec
and some few others strive for this figure, while others are looser and
some do not care--indeed, they like optimistic S-meters thinking hams are
gullible.

The S-unit proposal does not square with the concept of S in RST reports,
which recognizes only 1-9, even though the 6 dB standard would permit any
number of levels.  I have even heard a local VE claim that there is an S0
level (when the meter does not move), but this only shows that they have
not read into the history of the RST system of reporting in the mid 1930s
onward.  (Incidentally, VE means volunteer examiner, not my Canadian
neighbor.) S0 would mean that you are too weak to hear, but I shall
pretend you are there and tell that you are too weak to hear in any way,
shape, or form.  And S9 is as loud as the reporting systems permits, so
that any +xdB additions are really requests to reduce power (although few
take them as such).

The 1 S-unit=6 dB is most useful in comparisons of signal strength, both
in real time (flipping on your amp raised your signal by over 1 S unit or
10 dB) or when anticipating results (my new beam with 6 dB gain over the
old one should help by a full S-unit).  Since 3 dB = a power doubling or
halving, 6 dB equals an S unit = a power quadrupling or quartering--very
convenient--much more so than an alternative proposal of an S-unit = 5 dB.

It is unlikely that there will be any official standardization in the near
future on an industry-wide basis.

-73-

LB, W4RNL



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