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#1
12-21-2005, 05:17 AM
 Scitnor Guest Posts: n/a
(Power) Db to Watt

This is so simple, ...but I can't nail it!!

What is the conversion from Db to Watt?
#2
12-21-2005, 09:04 PM
 Robert Fogt Administrator Join Date: Dec 2005 Location: Seattle, WA Posts: 3,452 Rep Power: 13
Re: (Power) Db to Watt

0 decibel is equal to 1 picowatt per square meter. This corresponds to the faintest sound that can be detected by a person with good hearing.

A sound of 10 decibels means it is perceived as 10 times louder than 0 decibels.

Since decibels is a logarithmic unit of perceptive sound, I do not think there is a direct conversion between it and power.

I have seen conversions between decibel and power/area and between decibel and pressure, but I am fairly sure it would depend on the specific circumstances.

Perhaps someone in the audio field could shed more light on the subject.
#3
12-29-2005, 05:03 PM
 Scitnor Guest Posts: n/a
Re: (Power) Db to Watt

This would be power conversion in RF terms. ie., 20Db @ 850Mhz. There is a power value in Watts. As in, so many Db equals so many watts.

I'm not clear on the conversion???
#4
12-30-2005, 01:34 AM
 Robert Fogt Administrator Join Date: Dec 2005 Location: Seattle, WA Posts: 3,452 Rep Power: 13
Re: (Power) Db to Watt

This is the closest thing I could find on the topic:

#5
03-18-2006, 01:53 AM
 Unregistered Guest Posts: n/a
Re: (Power) Db to Watt

Quote:
 Originally Posted by Scitnor This is so simple, ...but I can't nail it!! What is the conversion from Db to Watt?
108 DB = WATT?
#6
06-07-2006, 07:58 AM
 Unregistered Guest Posts: n/a
Re: (Power) Db to Watt

dbm = 10^((WATTS - 30)/10)
#7
07-25-2006, 06:22 PM
 Locoguru Guest Posts: n/a
Re: (Power) Db to Watt

30db = 1 watt (1000 mw)
27db = .5 watts (500mw)

for each 3 db gain or loss it doubles or halves.

33db = 2 watts (2000mw)

36db = 4 watts (4000mw)

24db = .25watts (250mw)
#8
07-25-2006, 06:26 PM
 Locoguru Guest Posts: n/a
Re: (Power) Db to Watt

Forgot the formula!

Converting db to mw and mw to db

db=10*log(mw)
mw=anti-log(db/10)
#9
11-27-2006, 06:35 AM
 Unregistered Guest Posts: n/a
Re: (Power) Db to Watt

Quote:
 Originally Posted by Scitnor This is so simple, ...but I can't nail it!! What is the conversion from Db to Watt?
DBM - 30 divide by 10 Inv log

60 dbm -30= 30 Divide by 10 = 3 log of 3 = 1000
50 dbm -30 = 20 Divide by 10 = 2 log of 2 = 100

+60 dbm =1000 watts
+50 dbm = 100 watts

each 3 db is twice or 1/2 of starting power
#10
04-26-2009, 08:51 PM
 ZachFlem Guest Posts: n/a
Re: (Power) Db to Watt

I am trying to convert dBm to Watts and none of the formula described so far work.

I have a reliable conversion from watts to dbm, but I cant reverse the situation, the formulas here don't reverse the result.

I am trying to do this in Excel, it is being used in a calculator for a Wifi Link budget.

This is the current Watts -> dBm (works) =10*LOG10(D8/ 0.001)

and in its current form, dBm -> Watts (doesn't work) =LOG((D9-30)/10)

'D8' (watts) and 'D9' (dBm) accept input from a user =)

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