[Top][All Lists]

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [Discuss-gnuradio] The shortest pulse length

From: seph 004
Subject: Re: [Discuss-gnuradio] The shortest pulse length
Date: Fri, 2 Mar 2007 00:41:40 -0800 (PST)

I am only using 1 daughterboard. Sorry about the duc0 = 0 inclusion. It's something I neglected to remove when I was editing the original file. I don't think it should have any effect on what I am seeing though. I set the duc frequency to 0 because I wanted to transmit at baseband. I've already built the signal I want in the gr.vector, I just want the daughterboard to pass it as is. I've managed to do that with usrp_siggen.py. By setting the -f option to 0 and the -w option to some frequency, I get a waveform of the -w frequency at the daughterboard output. I'm pretty sure (0, 0) is TXA, and (1, 0) is TXB. My waveform does appear at the TXB output when I run the script. The problem is the pulse duration I'm seeing is much shorter (about 1/10) than what I expect.



----- Original Message ----
From: David Scaperoth <address@hidden>
To: seph 004 <address@hidden>
Cc: address@hidden
Sent: Thursday, March 1, 2007 7:15:36 PM
Subject: Re: [Discuss-gnuradio] The shortest pulse length

On 3/1/07, seph 004 <address@hidden> wrote:
This is what I did:

def build_graph ():
    nchan = 1
    interp = 512
    duc0 = 0
    duc1 = 0
    fs = 250e3                                        #2nd sample rate between usb and dac
    max_dev = 32e3                              #1st sample rate divided by 4 (1st = 2nd sample rate)
    gain = 16e3
    k = 2 * math.pi * max_dev / fs
    vec1 = Numeric.arange (0.624, 0.656, 0.0000128)
    vsource = gr.vector_source_f(vec1, False)
    fmmod = gr.frequency_modulator_fc (k)
    amp = gr.multiply_const_cc(gain)
    fg = gr.flow_graph ()
    u = usrp.sink_c (0, interp, nchan)
    tx_subdev_spec = (1, 0) #usrp.pick_tx_subdevice(u)
    m = usrp.determine_tx_mux_value(u, tx_subdev_spec)
    subdev = usrp.selected_subdev(u, tx_subdev_spec)
    sample_rate = u.dac_freq () / interp
    u.set_tx_freq (0, duc0)
    u.set_tx_freq (1, duc1)
Are you trying to use one daughter boards(nchen=1)?   Why did you set duc0 = 0?   that means your  frequency will not be set at all.  You do not need to do set_tx_freq() twice if you are using one daughter board.  you only need : u.set_tx_freq (0, duc0) where duc0 is some frequency.  Also, if you are using the basic daughterboards, you need to make sure that you have the output connector connect to TXA not TXB (according to your tx_subdev_spec)
Hope this helped.

Finding fabulous fares is fun.
Let Yahoo! FareChase search your favorite travel sites to find flight and hotel bargains.
reply via email to

[Prev in Thread] Current Thread [Next in Thread]