Re: [Discuss-gnuradio] Signal loss after a short time

[Ryan Seal]

Matt,

I solved this problem yesterday and it was my mistake. I measured the 
voltage levels of the internal oscillator with intentions of matching 
this level with my external clock. What I didn't see was the fact that I 
was measuring my levels with the "ac-coupled" setting on the scope. Too 
make a long story short, I needed to add a dc offset to my external 
clock to prevent the negative swings. Everything works perfectly now. I 
have been running the board for more than 24 hours without a problem. 
The past two systems I have worked with use an external clock directly 
from a frequency synthesizer so I think I was unconsciously making 
assumptions (bad news).

Thanks for the reply,
--Ryan

Matt Ettus wrote:
> Ryan,
>
> I am looking into this problem.  I will let you know if I find anything.
>
> You are using a 3.3V clock signal, right?
>
> Matt
>
> Ryan Seal wrote:
>   
> > When running both usrp_oscope and usrp_fft, I lose the signal and the
> > GUI becomes unresponsive after 5 - 30 minutes of operation. I had
> > previously ran this system for more than 24 hours with an installation
> > on a laptop back in July. Here is a short summary of my setup:
> >
> > 1. Dual HT Intel 64-bit processors with 32-bit Gentoo distribution.
> > 2. Latest dependencies from the portage tree (using ~x86 flag).
> > 3. I am using an external clock at 64MHz that will sync the USRP with
> > the rest of my system.
> > 4. I have an official USB 2.0 certified cable.
> >
> > To get the system back up and running properly, I either cycle power
> > (unplug the power supply) or run the usrper load_standard_bits
> > command. I also receiver failures when running the benchmark_usb
> > program maybe this is beginning to sound like a hardware problem ?
> >
> > --Ryan
> >
> >
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>
>