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[Discuss-gnuradio] DBSRX Modification and Antenna Bias Question

From: Eric Cottrell
Subject: [Discuss-gnuradio] DBSRX Modification and Antenna Bias Question
Date: Wed, 11 Jul 2007 18:33:10 -0400 (EDT)


The question: What is the maximum voltage I can put into the antenna bias 

The possible mod or configuration jumper:

I have a WR-LNA-3500 preamplifier that can be powered by coax or a coaxial 
power connector.  There is a diode to prevent backfeeding power through the 
receiver port if the coaxial power connector is used.  There is no shunt 
resistor to prevent diode leakage current from building up a voltage on the 
receiver port.  I measure 13.2 volts on my high impedance DVM at the receiver 
port with the preamplifier powered.

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.

73 Eric

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