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

[Nick Foster]

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
>