Re: [Discuss-gnuradio] Getting started with the USRP/RFX2400 and underflows

[Jason Uher]

On Tue, Jul 8, 2008 at 3:03 AM, Martin Braun <address@hidden> wrote:
> On Mon, Jul 07, 2008 at 04:32:47PM -0500, Jason Uher wrote:
>>   #Connect the sink to a SIN source
>>   src0 = gr.sig_source_c (48000, gr.GR_SIN_WAVE, 350, 0.5)
>>   fg.connect (src0, ut)
>
> This doesn't seem right. You're creating a sine wave w/ amplitude 0.5.
> In order to fully use the dynamic range of your USRP D/A converters, the
> signal needs to be somewhere in +-2^15. All you're transmitting is very
> quiet noise.

Thanks, that was definitely the problem.  I added a multiplier in
there and I can now hear the sine wave (faintly) behind all the
static.

Also, last night while trying to figure out how to test code with only
one usrp I came up with what now seems like an obvious solution.  I
transplanted the sine wave transmission code and plopped it into the
usrp_oscope script, forcing the oscope and transmitter to use the
correct devices, and now the signal shows up nice and clean on the
oscope display.

Jason