Message-ID: <01C3C0B2.09F37E10.g4jnt@thersgb.net>
From: "Andy talbot" <g4jnt@thersgb.net>
To: rsgb_lf_group@blacksheep.org
Date: Fri, 12 Dec 2003 13:15:37 -0000
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Subject: RE: LF: Related Technical Query - Soundcard calibrator
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Yes please, do that.  My feeling is that there 'has' to be a pi in there 
somewhere,
Errors in H&H aren't unknown...

I dislike SIN(X)/X calculations, they always involve PIs in strange places and 
never seem to plot out properly without some juggling of constants.

Andy G4JNT


-----Original Message-----
From:	James Moritz [SMTP:J.R.Moritz@herts.ac.uk]
Sent:	2003/12/12 11:17
To:	rsgb_lf_group@blacksheep.org
Subject:	RE: LF: Related Technical Query - Soundcard calibrator

Dear Andy, LF Group

I hate to throw a spanner in the works, but... A noise source of exactly
this type is discussed in Horowitz & Hill "The Art of Electronics" 2nd
ed., section 9.34. This gives the formula (in the form Andy has used)
Vrms^2 = Vpk^2 * 2 * BW /Fclock, (giving 224mV rms) which is different
by a factor of sqrt(pi) from the value Andy gets. I spent some time last
night trying to figure out which one is correct, and came out with a
reasonably convincing case for Horowitz & Hill's formula - if anyone is
interested, I will put it into an e-mail compatible form


Cheers, Jim Moritz
73 de M0BMU