Re: [Discuss-gnuradio] HELP: USRP1+WBXv3 "Overflow"

[Marcus D. Leech]

On 12/16/2014 12:24 AM, Thesis 2015 wrote:

Good day,

We are beginners using the USRP1 with WBX v.3 50-2200 daughterboard and GNU radio Companion version 3.7.5.1 with UHD_003.008.000-18-g864f84b5 installed on Ubuntu 14.04 LTS operating system. Our goal in using these is to create an SDR WBFM receiver.

We have followed what was done in the video posted by the ettus research (http://www.ettus.com/kb/detail/sdr-for-beginners-building-an-fm-receiver-with-the-usrp-and-gnu-radio) but have encountered some problems. As we ran the GRC file, both the FFT plot and Scope plot appeared but all we could hear are static sounds together with the script shown below:

Executing: "/media/thesis/Data/Downloads/Thesis/FM Reciever using GRC/fm_example.py"

linux; GNU C++ version 4.8.2; Boost_105400; UHD_003.008.000-18-g864f84b5

Using Volk machine: sse4_1_64_orc

-- Opening a USRP1 device...

-- Using FPGA clock rate of 64.000000MHz...

UHD Warning:

    The hardware does not support the requested RX sample rate:

    Target sample rate: 5.000000 MSps

    Actual sample rate: 5.333333 MSps

-- Tune Request: 88.100000 MHz

--   The RF LO does not support the requested frequency:

--     Requested LO Frequency: 88.100000 MHz

--     RF LO Result: 88.099634 MHz

--   Attempted to use the DSP to reach the requested frequency:

--     Desired DSP Frequency: -0.000366 MHz

--     DSP Result: -0.000366 MHz

--   Successfully tuned to 88.100000 MHz

-- 

INFO: Audio sink arch: alsa

OOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO

>>> Done

As we are doing all the simulations, we did not use any antenna yet. However, we are waiting for the arrival of the antenna LP0410 400 MHz to 1 GHz Log Periodic PCB directional antenna, at 5-6dBi Gain. We have purchased this antenna for it is capable to receive signals from 88.1MHz to 107.9MHz (frequency range of all the FM stations that we are about to receive).

-SKA15-

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The example is designed for an N200/N210, for which a 5Msps sample-rate is legal.

On the USRP1, the master-clock is at 64MHz, so you can't produce 5Msps from that, since that isn't an integer fraction of the master-clock rate.

Re-jig the graph to use 4Msps as the input sample-rate.  Pay attention to parts of the graph where it interpolates or re-samples, and make certain
  that re-sampling will still work with a 4Msps sample-rate.