R: [amsat-bb] Mode L/S

["i8cvs" <domenico.i8cvs@xxxxxx>]

Hi Karl, K5MAN

The isolation between 1.2 GHz and 2.4 GHz of your dual band patch is at
least 30 dB or 1000 time in power.
If you apply 2 watt at 1.2 GHz than the 23 cm power applied at the input of
your 2.4 GHz AIDC downconverter will be 2 mW or + 3 dBm
Even if your downconverter has not input filters +3dBm are not enough
to damage your GaAsFET or HEMT input device.
If your 1.2 GHz is overloading the 2.4 GHz front end than an open stub
1/4 wavelenght x velocity factor long at 1.2 GHz can be connected via a
coaxial T between your patch and the AIDC input.
The open end of the above 1/4 wavelenght long transmission line has in
theory an infinite impedance at the open end while the other end connected
to your ADIC converter represent a short circuit to the incoming 1.2 GHz
signal.

Are you counting the days for P3E to fly ?

Best 73" de

i8CVS Domenico


----- Original Message -----
From: Karl Sandstrom <k5man@cox.net>
To: <amsat-bb@amsat.org>
Sent: Tuesday, March 08, 2005 2:43 AM
Subject: [amsat-bb] Mode L/S


> I just put up a 36" dish with a W0LMD dual band patch feed for L/S.  It
has an
> K5GNA AIDC downconverter.  My 910 has the 1.2 ghz module and it has been
> tested to have about 10 to 12 watts of output power.  Unfortunately, the
cable
> I am currently using is 125 ft. long piece of 9913.  I figure I *might*
get 2
> watts to the patch.
>
> I know that there are issues with the 1.2ghz overloading the front end of
the
> 2.4ghz downconverter and that there are filters that can be bought or made
to
> help the problem.  My question is:  Are the overload problems so bad with
a
> patch that I may damage the downconverter or is it just a nuisance to the
> operator?
>
> Karl R. Sandstrom, K5MAN
> AMSAT Area Coordinator
> W5YI Volunteer Examiner
> Greenwell Springs, Louisiana
> k5man@arrl.net / k5man@amsat.org
> ----
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