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Re: [Discuss-gnuradio] Changing Bandwidth USRP
From: |
Marcus Müller |
Subject: |
Re: [Discuss-gnuradio] Changing Bandwidth USRP |
Date: |
Fri, 04 Oct 2013 13:41:22 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130923 Thunderbird/17.0.9 |
This is a completely different problem, is it? Bandwidth is orthogonal to the
concept of dynamic range and amplitude values.
Anyway, your FFT plot knows about complex samples; therefore, it displays dB relative to
the numeric value of "1.0"; this has nothing to do with your input signal
power. But since USRP/daughterboards tend to work linearly over most of their available
power range, you can just add a multiply_const to your signal processing flowgraph and
get your value.
The factor, however, depends on your ADC/daughterboard combination, on the gain you set
for the RF frontend, a little bit on temperature, the tuner, the impedance matching of
your RF input to the Daughterboard etc. So if you already know what you're putting in,
just use this as a reference and "calibrate" yourself.
Hope that helped clear things up,
Marcus
On 10/04/2013 01:05 PM, Antmrt wrote:
Thanks Marcus, my problem is how to calibrate the scale on the FFT plot. e.g:
I'm feeding a signal of -30 dBm to the usrp and on the plot the value
becomes about -10 dBm
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