[Fwd: LF: Rcvr - why not measure noise floor?]

[Andre' Kesteloot]

Andy Talbot wrote:

> >I agree that the sensitivity is not of great value to extimate an LF RX.
> >
> >But why those tests are not done measuring the usual 3 db S+N/N ratio?
> >This will be much more useful, and not ear-depending. Knowing this number
> >you may scale the signal to other BW and other ears.
> >
> >Also, since the 3 dB MSD/noise floor level is higher you reduce the
> >possibility
> >of ground loops and so ...
> >
> >Oh well, you need a true RMS audio voltmeter, but today it is really
> >inexpensive
> >(few US$ or £ or Euro for an HP 3400A).
>
> When testing with a tone, obtaining the 3db point  still leadds to
> uncertainty in the effective receiver noise bandwidth.  A spectrum display
> produced by a DSP system has a precisely defined noise bandwidth, and S/N
> can be determined with great accuracy
>
> Andy