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[Discuss-gnuradio] Maximum antenna input voltage on LFRX

From: Nick Smith
Subject: [Discuss-gnuradio] Maximum antenna input voltage on LFRX
Date: Fri, 24 Dec 2010 15:37:44 -0800 (PST)

I've looked through the mailing list archive and found a few messages related 
to this, but they referred to signal generators and power in dBm.
In my case, I plan to use it with an antenna and eventually a pre-amp. However, 
I've found that by measuring the voltage from even a 3ft (90cm) antenna using a 
multimeter with a probe on the antenna and a probe to ground gives a reading of 
four volts RMS. With a 25ft (7.6m) antenna, I can slightly light up an LED (I 
don't remember the voltage), and with a 100ft (30.5m) antenna, I got about 140V.

On http://gnuradio.org/redmine/wiki/gnuradio/UsrpFAQDBoards , under the 
question "If I want to apply the output (50 ohm) from a function generator 
directly to the BasicRX inputs, what is the allowed voltage range that can be 
applied?", it states "3V p-p should be safe, since it won't exceed the 3.3V 
supply voltage."
While that is for the BasicRX, I assume another limit exists with the LFRX.

I just want to confirm that I won't break anything if I attach an antenna.

Thanks for your time!

--- Nick


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