R: [amsat-bb] S units

["i8cvs" <domenico.i8cvs@xxxxxx>]

Brian and All,

For 30 MHz and lower S 9 = -73 dBm available signal power at the receiver
input

For 144 MHz and above S 9 = -93 dBm of available signal power at the
receiver input.

To convert dBm to microvolt, recall that E= SQR (R x P ) where E is in volt
R is resistance in ohm and P is power in watt.

Example:

Since -93 dBm is 5,011 x 10 E -13 watt, than -93 dBm is equivalent to
5 microvolt across a 50 ohm input termination.

However, for a matched signal  generator where the output impedance
is equal to the RX input impedance  i.e. Z=50+j0  ohm, the generator voltage
must be twice the voltage across the receiver input because of the voltage
dividing effect of the two series impedances in the network.

For a matched 50 ohm source, therefore, an input signal of -93 dBm
corresponding to S 9 at 144 MHz and up requires a generator voltage
of 10 microvolt.

Similarly, for 30 MHz and lower an input signal of -73 dBm corresponding
to S 9 requires a generator voltage of 100 microvolt in a matched 50
ohm system.

73" de

i8CVS Domenico

----- Original Message -----
From: Brian <groupes@smart-tech.dk>
To: <amsat-bb@AMSAT.Org>
Sent: Monday, October 06, 2003 5:02 PM
Subject: Re: [amsat-bb] S units


>
> ----- Original Message -----
> From: "i8cvs" <domenico.i8cvs@tin.it>
> To: "Gerald Horn" <ghorn666@earthlink.net>; "AMSAT-BB"
<amsat-bb@AMSAT.Org>
> Sent: Monday, October 06, 2003 3:45 PM
> Subject: R: [amsat-bb] S units
>
>
> > The S 9 reference level for frequency bands above 144 MHz is -93 dBm
> > available signal power at the receiver input.
>
> What about below 144MHz?
>
> > 73" de
> >
> > i8CVS Domenico
>
> Regards
> Brian OZ1SKY
>
> ----
> Sent via amsat-bb@amsat.org. Opinions expressed are those of the author.
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