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R: Re: How far should one separate a LNA and its associated down converter, and Why?




----- Original Message -----
From: Bill Acito W1PA <w1pa@hotmail.com>
To: <amsat-bb@AMSAT.Org>
Sent: Monday, April 07, 2003 4:47 AM
Subject: [amsat-bb] Re: How far should one separate a LNA and its associated
down converter, and Why?


> > I also experienced 13ULNA preamp instability and solved it by putting
> a 1"
> > square piece of black anti-static foam in the DEM enclosure.  It was
> about
> a
> > 1/4" thick.  My 13ULNA is connected to my downconverter through a
> double
> > male N barrel connector.
> >
>
>
> While I am digging up the QEX reference, can the same thing be
> accomplished by putting additional shielding (a copper or brass plate)
> immediately over the ULNA board, in close proximity? I worry about the
> foam breaking down and shedding.
>
> Bill
> w1pa
>

Bill,

Additional shielding inside the box immediatley over the LNA board do
not prevent the RF energy to transfere from one stage to the previous
one inside the box.

On the other hand the conductive black foam absorbes and dissipates
the circulating RF  fields inside the box and it make very easy to cut
regenerative feedback  between the input and output of low signal  and
high gain amplifiers.

Dont worry about the possibility of foam breaking down is you use a
good quality elastic glue like BOSTICK for example.

73" de i8CVS Domenico

> ----
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