[BC] dbu to microvolt program

[Peter Burk]

Richard,

dBu, as used in RF, is referenced to 1uV/meter. Only at about 40MHz is dBu
equal to dBuv, which presumably references to 1 1 microvolt.  To see this in
the spreadsheet, first convert 1uV into dBm, assuming 50 ohms (equation 4)
which is -106.99 dBm, then convert that using equation 8, yielding dB above
1uV/meter. You'll see that at 100MHz, 1uV is 8 dBu. You simply can't get dBu
from microvolts without the frequency.

In audio, dBu is sometimes used to state voltages referenced to 0.775vrms.
Seems like dBm does this well enough, but pick your standard. It's nice to
have so many to choose from.

Equations 2 thru 8 all use the 2 formulas you gave as their root and yes,
they are valid. 

Peter Burk
Burk Technology

-----Original Message-----
From: Richard Fry [mailto:rfry at adams.net] 
Sent: Monday, April 09, 2007 10:00 AM
To: Broadcast List
Subject: [BC] dbu to microvolt program

Peter Burk:
>dbu is frequency dependent. .
___________

Agree that the amount of voltage that an antenna can produce from being
immersed in a radiated field is frequency-dependent, as well as being
dependent on the antenna design, its physical orientation, line loss, and
the impedance across which that voltage is developed at the point of
measurement.

But any radiated or conducted voltage, once known, can be converted from
units of volts to X dB with respect to that value, at that point of
measurement.  They are just different forms of the same number. So the
simple equations I posted earlier will be valid.

There is an equation that relates the amount of voltage at a point in a
conducted circuit to the amount of arriving field at the antenna that it
will take to generate that voltage.  That does include consideration of the
frequency (plus more).

RF 

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