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Old September 15th 04, 11:56 AM
Thierry
 
Posts: n/a
Default dBW in S-unit and power strenght

Hi,

A question about dBW and power at receive.
Among scales used in power measurement, there is the signal strength or
noise level estimation, also known as the "dB below W" (dBW or SDBW). Its
relation is dBW = 10 Log P, where P is the power expressed in watt :
That means that 100 W is 20 dBW into 50 ohms.

But usually, in propagation program (VOACAP, etc), the power strength at
receive expressed in dBW is far below such values. I read somewhere the next
equivalences :
- (minus) 93 ~ S9+10, -103 = S9, -127 = S5, -151 = S1.

With -93 dBW for a S9+10 signal at receive, that 'd mean that the power 'd
be only P(W) = 10^ (dBW/10) = 0.7 watt ?
IMHO this power is much to low... What is wrong in this relations (or in my
interpretation) ?

Thanks in advance

Thierry, ON4SKY
http://www.astrosurf.com/lombry