Re: [Discuss-gnuradio] WBX and frequencies around 433 MHz?

[Patrik Eliardsson]

Nick,

I tuned the center frequency to 400 MHz, 430 MHz and 433 MHz and the LO is 
locked for all of them.

The spectrum for 430 MHz looks like the spectrum for 433 MHz (white line) in my 
previous post. I've tried the same thing on another USRP2 with another WBX and 
I get similar spectrums. So it doesn't happen on just one device.

BTW, I like the probe block, didn't know it before. It can be useful for other 
purpose aswell.

Br,
Patrik

> Patrik,
> 
> Can you please check to see that the WBX LO is locked? If you 
> have a GRC flowgraph, you can use a function probe block with 
> the following
> settings:
> 
> ID: lo_locked
> Block ID: uhd_usrp_source_0  (or whatever your UHD source 
> block is named) Function name: get_dboard_sensor Function 
> args: '"lo_locked", 0'
> Poll rate: 1
> 
> Then use a WXGUI checkbox with a default value set to bool(lo_locked).
> When you run your flowgraph, the checkbox will indicate 
> whether the LO is locked.
> 
> In your own non-GRC application you can use <usrp source
> name>.get_dboard_sensor("lo_locked", 0) to check the status of the
> daughterboard LO lock.
> 
> --n
> 
> On Tue, Dec 6, 2011 at 4:40 AM, Patrik Eliardsson 
> <address@hidden> wrote:
> >> > > Hi,
> >> > >
> >> > > While I was testing the DQPSK-(de)modulation blocks in GRC.
> >> > I found a frequency region where the reception failed. I
> >> started with
> >> > the ISM-band (433 MHz) as the center frequency, and the 
> reception 
> >> > didn't work. After checking my code several times I decided
> >> to change
> >> > the center frequency to 2 GHz and everything started to 
> work. So I 
> >> > tried several other center frequencies with successful 
> outcome, for 
> >> > example 2 GHz, 1.5GHz, 800MHz, 500MHz, 420MHz. If I tuned the 
> >> > frequency to the 430-440 MHz region the reception fails.
> >> > >
> >> > > I've used 2 USRP2s with the WBX and connected them with a
> >> > cable and 20 dB attenuator.
> >> > >
> >> > > I have 4 different WBX cards and the result is the same for
> >> > each of them.
> >> > >
> >> > > Have someone encountered the same problem with frequencies
> >> > around 433 MHz?
> >> > >
> >> > > Br,
> >> > > Patrik
> >> > >
> >> > >
> >> > Well, there's a lot of amateur radio traffic in that
> >> frequency range,
> >> > which may be interfering.
> >>
> >> I will keep that in mind. But I used a cable between the 
> USRP2s, so I 
> >> wouldn't expect any interference from other systems.
> >>
> >> > Also, there's a special frequency at 433.920MHz used for
> >> garage door
> >> > openers.  Are you running
> >> >   your USRP2 with the covers on or off?
> >>
> >> The covers are on.
> >>
> >> I will have a look at the received spectrum again, as Nick 
> suggested.
> >
> >
> > Please have a look at the attached spectrum.
> >
> > Cable.png shows the spectrum when the transmitter is 
> connected to the spectrum analyzer with a cable and 20 dB 
> attenuator. The white line is the spectrum at the center 
> frequency 433 MHz and the yellow line is at 400 MHz. The 
> spectrum for 433 MHz looks like crap.
> >
> > Figure 400.png and 433.png shows the received constellation 
> points and the received spectrum after a LPF for 400 MHz and 433 MHz.
> >
> > -Patrik
> > _______________________________________________
> > Discuss-gnuradio mailing list
> > address@hidden
> > https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
> >
>