[Premium-Rx] RA6793A Sensitivity?

[lb]

Raymond,

No such error exists in the definition of the Bel or its
derivatives (decibel, millibel, microbel, megabel, etc.).

They express a power ratio, i.e. Pin / Pout or vice versa.

The numbers used are logarithms: (log Pin) / (log Pout).
The base 10 log is used.

Since power = voltage squared / resistance, and the
resistance of both measurements should be equal...

the voltage ratio in Bels is (log Vin^2) / (log Vout^2).
For decibels it's (10 log Vin^2) / (10 log Vout^2).

Since exponentiation factors out in logarithms, that
becomes decibels = (20 log Vin) / (20 log Vout).

That's why half power = 3db and half voltage = 6db.
Similarly, 10x power = 10db and 10x voltage = 20db.

Basic electronic analysis.

- de Leigh W3NLB

From: Raymond Boute <raymond.boute at pandora.be>
Date: 4/8/17  2:16 AM  (GMT-05:00)
To: fintronicsusa <fintronicsusa at gmail.com>
Subject: Re: [Premium-Rx] RA6793A Sensitivity?
Dear Glenn,
Due to a quirk (actually a design blunder) in the definition of the
decibel, the amount in decibel is doubled for voltages as compared to
powers.  Furthermore, the impedance of your source must be matched to 
the Rx.