[Elecraft] XG-1 MDS Calculation

[Robert Friess]

The meter is part of it.  An average reading meter calibrated for a sine
wave will measure noise about 1 dB lower than the actual power.  In this
case that would cause the MDS to be 1 dB worse than measured.  Also, it is
expected that there will be a variation of a dB or two from one radio to the
next which may explain the rest.

73,
Bob, N6CM

----- Original Message ----- 
From: "Bill Tippett" <btippett at alum.mit.edu>
To: "Robert Friess" <rfriess at usa.net>; <elecraft at mailman.qth.net>
Sent: Monday, May 17, 2004 1:13 PM
Subject: Re: [Elecraft] XG-1 MDS Calculation


> At 03:33 PM 5/17/04, NC6M wrote:
> >The definition of MDS is a signal that is equal in power to the noise
> >present in the channel.  When the s+n/n ratio is 3 dB this condition is
met
> >with the signal and the noise each making an equal contribution to the
total
> >power.  In the case of a measurement made with the XG1, the s+n/n ratio
is
> >much greater than 3 dB and the contribution of noise to the total power
> >measured in the channel is negligible, therefore the  MDS is simply equal
> >to -107dBm - s+n/n.
>
>          Thanks Bob, but then I'm wondering about the apparent discrepancy
> between measurements with my XG-1 and ARRL's measurements.  I assume
> I should still normalize any actual BW difference (to the 500 Hz
standard).  I
> thought I had the difference nicely explained with the additional 3 dB in
> the MDS definition, but your comment leaves me wondering why I'm now
> measuring MDS 3 dB lower than ARRL's measurement.  Any ideas?  Could it
> be due to using an average-responding instead of RMS-responding meter?
>
>                                  73,  Bill  W4ZV
>
>
>