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#1




converting dBm to uV/m
Hey all,
I'm still skeptical about this formula: Field Strength (uV/m) = 10 ^ ( (107  dBm ) / 20 ) Is this valid? I saw this formula somewhere and jotted it down. Thanks! 
#2




converting dBm to uV/m
Ron J wrote:
Hey all, I'm still skeptical about this formula: Field Strength (uV/m) = 10 ^ ( (107  dBm ) / 20 ) Is this valid? I saw this formula somewhere and jotted it down. Thanks! dBm is a measure of power, and the field strength as a function of power is going to depend on antenna characteristics. The equation you have is a pretty direct conversion between power in dBm to voltage, with a magic proportionality factor (the 107) buried in the exponent. So I suspect it's a valid function, but only for one type of antenna.  Tim Wescott Wescott Design Services http://www.wescottdesign.com 
#3




converting dBm to uV/m
There's not enough information to calculate field strength. There's a
direct relationship between uV/m (field strength) and W/m^2 (power density), providing you're in the far field and you know the intrinsic impedance of the medium (about 377 ohms for free space). But you need a distance from the source and the antenna gain in order to know what the power density is for a given power (dBm). So at the very least, you have to specify the distance from the source and the antenna gain to calculate field strength from dBm. And then it's valid only in the far field. Roy Lewallen, W7EL Ron J wrote: Hey all, I'm still skeptical about this formula: Field Strength (uV/m) = 10 ^ ( (107  dBm ) / 20 ) Is this valid? I saw this formula somewhere and jotted it down. Thanks! 
#4




converting dBm to uV/m
dBm significant the logarithm relation to Power (mW). In case of field
strength or voltage (mV) you have to multiplication with 20. Take a look at: http://www.sengpielaudio.com/calculatorvolt.htm http://www.nobbi.com/conversion.htm and very good: http://en.wikipedia.org/wiki/Decibel Regards, Ralf  Vy 73 es 55 de Ralf, DL2MRB EMail: www.hamradioboard.de 
#5




converting dBm to uV/m
On 28 Dec 2005 10:53:34 0800, "Ron J" wrote:
Hey all, I'm still skeptical about this formula: Field Strength (uV/m) = 10 ^ ( (107  dBm ) / 20 ) Is this valid? I saw this formula somewhere and jotted it down. Your expression does not apply in general, it is the unstated assumptions that are the issue (freq, receiver R, antenna factor. bandwidth). The calculator at http://www.vk1od.net/sc/FS2RPCalc.htm my be of interest. Owen Thanks!  
#6




converting dBm to uV/m
On Wed, 28 Dec 2005 21:38:46 GMT, Owen Duffy wrote:
On 28 Dec 2005 10:53:34 0800, "Ron J" wrote: Hey all, I'm still skeptical about this formula: Field Strength (uV/m) = 10 ^ ( (107  dBm ) / 20 ) Is this valid? I saw this formula somewhere and jotted it down. Your expression does not apply in general, it is the unstated assumptions that are the issue (freq, receiver R, antenna factor. bandwidth). With an Antenna Factor of 0dB/m (eg 0dBi gain at 30.83... MHz), a rx power of 0dBm/Hz in a matched receiver, would be the result of a field strength of ~107dBuV/m/Hz. So, the lhs of your formulat is in units of dBuV/m, and assumes AF=0dB/m and 1Hz bandwidth. AF depends on antenna gain and frequency, and antenna / receiver R. Owen The calculator at http://www.vk1od.net/sc/FS2RPCalc.htm my be of interest. Owen Thanks!  
#7




converting dBm to uV/m
Everything you need plus!!!!
http://www.sengpielaudio.com/Calculations03.htm Bill "Ron J" wrote in message oups.com... Hey all, I'm still skeptical about this formula: Field Strength (uV/m) = 10 ^ ( (107  dBm ) / 20 ) Is this valid? I saw this formula somewhere and jotted it down. Thanks! 
#8




converting dBm to uV/m
On Thu, 29 Dec 2005 06:57:40 0500, "Bill"
wrote: Everything you need plus!!!! http://www.sengpielaudio.com/Calculations03.htm A page full of calculators Bill, can you be more specific about a URL for one that converts field strength to received power or viceversa? Bill "Ron J" wrote in message roups.com... Hey all, I'm still skeptical about this formula: Field Strength (uV/m) = 10 ^ ( (107  dBm ) / 20 ) Is this valid? I saw this formula somewhere and jotted it down. Thanks!  
#9




converting dBm to uV/m
On Wed, 28 Dec 2005 22:22:04 +0100, Ralf Ballis  DL2MRB
wrote: dBm significant the logarithm relation to Power (mW). In case of field strength or voltage (mV) you have to multiplication with 20. Take a look at: http://www.sengpielaudio.com/calculatorvolt.htm http://www.nobbi.com/conversion.htm and very good: http://en.wikipedia.org/wiki/Decibel Do any of these actually deal with field strength to receive power conversion? Regards, Ralf  
#10




converting dBm to uV/m
Owen Duffy wrote:
Do any of these actually deal with field strength to receive power conversion? At starting point I would say yes for those how know to use it. Regards, Ralf  Vy 73 es 55 de Ralf, DL2MRB EMail: www.hamradioboard.de 
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