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R: Input impedance of DEMI2400-144RX?




----- Original Message -----
From: i8cvs <domenico.i8cvs@tin.it>
To: AMSAT-BB <amsat-bb@amsat.org>; Scott Townley <nx7u@arrl.net>
Sent: Tuesday, July 24, 2001 3:41 PM
Subject: R: [amsat-bb] Input impedance of DEMI2400-144RX?


> Hi  Scott,
>
> If the input device of DEMI2400-144RX is a GaAsFET and if the input
network
> has been adjusted for the lowest Noise Figure to 50 ohm input,than the
> reflection coefficient S11 allow you to get at best a return loss of  3 to
4
> dB or an input VSWR very high around 5 or 6.
>
> Such high input VSWR is normal in a devices such a GaAsFET adjusted for
the
> lowest Noise Figure.
>
> If you look at the scattering parameters of a GaAsFET for minimum noise ad
> make an exercise using PUFF,Computer Aided Design for Microwave Integrated
> Circuits Version 2.0 you will get the answere to your question.
>
> PUFF is widely used in Europe and originated as a teaching tool for
> Caltech's microwave circuits course by professors:
>
> Scott W. Wedge
> Richard Compton
> David Rutledge
>
> PUFF Distribution
> Electrical Engineering M/S 116-81
> California Institute of  Technology
> Pasadena, CA 91125
>
> FAX to (818) 356-2137
>
> 73 de i8CVS Domenico
>
>
> ----- Original Message -----
> From: Scott Townley <nx7u@arrl.net>
> To: <amsat-bb@AMSAT.Org>
> Sent: Monday, July 23, 2001 1:37 AM
> Subject: [amsat-bb] Input impedance of DEMI2400-144RX?
>
>
> > Has anyone measured the input impedance/VSWR of the DEMI 2400-144RX
> > downconverter?
> > Trying to assess whether mine is nominal or not.
> > So far have measured 20dB conversion gain but input VSWR is very high,
> > which may mean nothing depending on the design philosophy.
> > TIA,
> > Scott Townley
> > nx7u@arrl.net
> > ----
> > Via the amsat-bb mailing list at AMSAT.ORG courtesy of AMSAT-NA.
> > To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org
> >
>
>
>
>
>
>
>
>



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