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Re: [Discuss-gnuradio] DBSRX Modification and Antenna Bias Question

From: Matt Ettus
Subject: Re: [Discuss-gnuradio] DBSRX Modification and Antenna Bias Question
Date: Wed, 11 Jul 2007 15:58:09 -0700
User-agent: Thunderbird (X11/20070326)

> In looking at the schematic of the DBSRX I noticed there is no real DC path 
> to ground when DC Bias is not used.  Would there be any problem to either 
> jumper the DC Bias connector when not used or to add a high value shunt 
> resistor across the DC Bias connector to keep any DC levels down?  I assume 
> the choke will keep most of the RF on the proper side.

Shorting J101 puts 5 Volts (up to 500 mA I believe) on the antenna line.
Applying voltage to J100 pin 1 allows you to send bias other than 5V.

The DC-blocking cap to the LNA should be good to 50V, but I wouldn't
push it.

Shorting across J100 would give a DC short to your amplifier, which
seems ok from the DBSRX side, but make sure your amp won't send
significant current down that line.


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