[amsat-bb] Re: AO27/TS2000

Edward R. Cole kl7uw at acsalaska.net
Sat Jul 31 13:15:44 PDT 2010

At 11:28 AM 7/31/2010, i8cvs wrote:
>----- Original Message -----
>From: <wa4hfn at comcast.net>
>To: "AMSAT" <amsat-bb at amsat.org>
>Sent: Saturday, July 31, 2010 8:45 PM
>Subject: [amsat-bb] AO27/TS2000
> >
> >
> > Just installed a preamp Ar2 { Advance Reciever Research) M# MSP432DG-160
>and the birdy that the TS2000 has on AO27 recieve is now gone and I was able
>to hear the bird from start of the pass to the end.Why ,I do not know, but
>the preamp seems to kill the birdy . Has anyone found this to be the same.
> >
> > WA4HFN Damon
> > _______________________________________________
>Hi Damon, WA4HFN
>The pramplifier "seems" to kill the birdy because the preamplifier gain is
>very high and so the birdy is belove the noise introduced by the
>preamplifier itself.
>I guess that without any signal on the band your S meter reading is well
>above S-9 only because of the preamplifier noise that is apparently killing
>the birdy.
>If you reduce the gain of your preamplifier to get an S-meter reading of say
>S-1 or S-2 without any signal on the band then the birdy will appear again.
>Best 73" de
>i8CVS Domenico
>Sent via AMSAT-BB at amsat.org. Opinions expressed are those of the author.
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Not sure this is the same explanation as Domenico gave, but, if the 
birdie is internal to the radio, running an external preamp operates 
the radio at a signal (plus noise) level above the level of the birdie.

The noise rises due to the exta gain but the noise floor actually can 
be lower due to the increase in sensitivity (lower noise 
figure).  Does this make sense?  In other words, the radio may go 
from operating at -122 dBm to operating at -110 dBm (if preceded by 
22-dB gain) and the receiver system (Rx+preamp) operate at -132 dBm 
(not necessarily what your system will do).  The birdie is not 
amplified but the signal+noise is.  This usually does not help with 
birdies external to the radio.

73, Ed - KL7UW, WD2XSH/45
BP40IQ   500 KHz - 10-GHz   www.kl7uw.com
EME: 144-QRT*, 432-100w, 1296-QRT*, 3400-fall 2010
DUBUS Magazine USA Rep dubususa at hotmail.com

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