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

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

  
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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