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Re: [Discuss-gnuradio] Understanding the limitations of USRP1


From: Vanush Vaswani
Subject: Re: [Discuss-gnuradio] Understanding the limitations of USRP1
Date: Thu, 12 Feb 2015 18:35:08 +1100

Aliasing on purpose?

On Thu, Feb 12, 2015 at 11:25 AM, Marcus D. Leech <address@hidden> wrote:
> On 02/11/2015 06:15 PM, Tommy Tracy wrote:
>
> I am using a USRP1, and I'm trying to receive FM radio. I'm using a BasicRX
> daughterboard with a 0-250MHz range. The USRP itself has a LO frequency of
> 64MHz. Does this limit my frequency range to 0-32MHz, or can I get into the
> 100MHz range by somehow multiplying that Local Oscillator frequency?
>
> I get the following error:
>
> -- Opening a USRP1 device...
> -- Using FPGA clock rate of 64.000000MHz...
> -- Tune Request: 102.900000 MHz
> --   The RF LO does not support the requested frequency:
> --     Requested LO Frequency: 102.900000 MHz
> --     RF LO Result: 0.000000 MHz
> --   Attempted to use the DSP to reach the requested frequency:
> --     Desired DSP Frequency: -102.900000 MHz
> --     DSP Result: 25.100000 MHz
> --   Successfully tuned to -25.100000 MHz
>
> --
> --
>          Sincerely,
> Tommy James Tracy II
>      Ph.D Candidate
> Computer Engineering
>   University of Virginia
>
> _______________________________________________
> Discuss-gnuradio mailing list
> address@hidden
> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
>
> You might be better off getting a TVRX2 card for it.
>
> You're limited on the USRP1 to 64Msps, and since the BASIC_RX does no
> downconversion--it's just an ADC "buffer", you'd be limited to <= 32MHz in
> the
>   first Nyquist zone.
>
> You *could* put a very stiff FM-band-only filter and some gain in front of
> the BASIC_RX, and calculate the appropriate "Nyquist folding" for your
> desired
>   frequencies, and tune to those frequencies in the DC-32Mhz region.
>
>
>
> --
> Marcus Leech
> Principal Investigator
> Shirleys Bay Radio Astronomy Consortium
> http://www.sbrac.org
>
>
> _______________________________________________
> Discuss-gnuradio mailing list
> address@hidden
> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
>



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