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From: larry@kitty.UUCP (Larry Lippman)
Newsgroups: sci.electronics
Subject: Re: VHF tranceiver specs
Summary: SINBAD rating for marine radios
Message-ID: <3899@kitty.UUCP>
Date: 29 Jul 90 04:10:18 GMT
References: <1990Jul29.015732.21869@phri.nyu.edu>
Organization: Recognition Research Corp., Clarence, NY
Lines: 42

In article <1990Jul29.015732.21869@phri.nyu.edu>, roy@alanine.phri.nyu.edu (Roy Smith) writes:
> 	I'm trying to compare several Marine VHF/FM tranceivers.  In the
> spec sheet, there are figures for Sensitivity, subheading "12 dB SINAD".
> I've never seen the acronym SINAD before; what does it mean?  The ratings
> run from 0.20uV to 0.35uV.  Are these good numbers?  They also list "20 dB
> quieting" (0.25uV to 0.40uV), but I'm not sure exactly what that means
> either.

	Your data sheet must have a typographical error.  In the particular
case of marine radios, the acronym SINBAD is used, which is a subjective
sensitivity rating originated by Sinbad the Sailor.

	I'm sorry; the Devil grabbed hold of my keyboard and made me write
the above.  :-)

	Seriously, though, SINAD is a widely accepted approach for the
specification of receiver sensitivity.  SINAD is an EIA method which
expresses in decibels the ratio of [SIGNAL + NOISE + DISTORTION] to
[NOISE + DISTORTION].  A 12dB ratio is used as an arbitrary point for
reference sensitivity.  The 12 dB merely indicates the measurement
ratio, and is not a specification for the receiver per se.

	12 dB SINAD sensitivities of 0.20 uV to 0.35 uV are good numbers;
offhand, on a top-of-the-line commercial VHF-FM radio radio like say,
the Motorola Micor, I don't ever recall seeing anything better than
0.175 uV - and that was with the preamp option.

	20 dB quieting sensitivity is used as a means to express the
noise figure of the radio in uV as opposed to dB.  The 20 dB is a fixed
ratio used to define a measurement condition.  The 20 dB quieting
sensitivity will always be a higher value than the 12 dB SINAD value.
The figures you give above are good numbers, and they don't get any
better for this type of radio.

	A specification which you haven't mentioned is EIA SINAD
selectivity, which would be my next concern.  I would not settle for
anything less than -95 dB @ +/- 30 kHz.  In addition, I would look
for spurious and image rejection of at least 95 dB.

Larry Lippman @ Recognition Research Corp.  "Have you hugged your cat today?"
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