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Re: Re: AMSAT-BB-digest V2004 #967



----- Original Message -----
From: "Kyle Yoksh" <yokshs@totalusa.net>
To: <amsat-bb@amsat.org>
Sent: Thursday, December 01, 2005 3:24 PM
Subject: [amsat-bb] Re: AMSAT-BB-digest V2004 #967


> ----- Original Message -----
> > Date: Wed, 30 Nov 2005 23:56:58 -0500
> > From: "GEORGE ABBOTT"
> > Subject: RE: [amsat-bb] HRD and two radios: was dual IC-706 station
> >
> > Hi:I was told that they lack the necessary sensitivity for SSB signal
> > detection in the vhf and uhf bandwidths.
>
> Hi George,
>
> Thanks for the reply. I did some checking, and there is something to what
> you've heard. The first generation (MKI) 706 models show .16 uV
sensitivity
> at 144 MHz with the preamp on.
>
> The spec on my MK2g is .11 uV, same as the IC-910.
>
> Good to know - I had no idea that Icom improved the sensitivity from MKI
to
> MKIIg.
>
> Under 144 MHz the specs on the two rigs are about the same.
>
> 73,
>
> Kyle Yoksh
> K0KN
> Olathe, Kansas
> Amsat# 35249

Hi Kyle, K0KN

Quoting the sensitivity in uV without specifing for how many dB
of S/N ratio or (S+N)/N ratio the sensitivity is given and without 
mentioning the band width and the mode of operation for wich the 
sensitivity is specified it means very small and it make impossible 
to compare one receiver to another one.

For example a  FT-736 at 144 MHz in to a BW of 2.5 KHz for SSB
has the following specifications:

Sensitivity =  -15 dB uV for a ratio (S+N)/N = 12 dB

The above is equivalent to a sensitivity of 0.177 uV  for a ratio
(S+N)/N = 12 dB or to a sensitivity of 0.177 uV for a ratio
S/N = 11.71 dB

The above sensitivity is intended when a signal of 0.177 uV is
applied across the 50 ohm nominal RX input impedance.

If a signal of 0.177 uV applied to the RX input is capable to produce a
ratio of (S+N)/N = 12 dB at the RX output than the RX noise figure
NF= 6.27 dB

If someone is interested to know how the above numbars are derived
in order to compare receivers please let me know.

Best 73" de

i8CVS Domenico
----
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