aUaUaUaUaUaU and requested rx frequency not supported problem

Hi Everybody,
I am using USRP with daugherboard of range 1MHz to 250MHz. I am running
the program with gnu-radio 3.6.0 on Ubuntu 11.10. I am trying to run the
basic fm receiver program as shown in the video.

Whenever I try to execute the code, I get following things on grc. I
have
double checked that the daughterboard works for the range. When I see
the
fft plot of the received signal I see that I have just noise all around.
The hardware does not support the requested RX frequency:
Target frequency: 100.000000 MHz
Actual frequency: -28.000000 MHz
aUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaU

I have also tried to see if the antenna choices are correct. I checked
it
with uhd_usrp_probe
The important part of the result was
RX Subdev: AB
| | | | Name: Basic RX (0x0001) - AB
| | | | Antennas:
| | | | Sensors:
| | | | Freq range: -250.000 to 250.000 Mhz
| | | | Gain Elements: None
| | | | Connection Type: IQ
| | | | Uses LO offset: No
| | | _____________________________________________________
| | | /
| | | | RX Subdev: BA
| | | | Name: Basic RX (0x0001) - BA
| | | | Antennas:
| | | | Sensors:
| | | | Freq range: -250.000 to 250.000 Mhz
| | | | Gain Elements: None
| | | | Connection Type: QI
| | | | Uses LO offset: No

So, when I try to work with uhd_fft. I got same problem with following
results
uhd_fft --spec B:AB

linux; GNU C++ version 4.6.1; Boost_104601; UHD_003.004.001-39-unstable

– Opening a USRP1 device…
– Using FPGA clock rate of 64.000000MHz…
Using Volk machine: ssse3_64

UHD Warning:
The hardware does not support the requested RX frequency:
Target frequency: 100.000000 MHz
Actual frequency: -28.000000 MHz

Could you help me out here?
Thanks in advance.

– Pranav Sakulkar

On Fri, 11 May 2012 19:08:38 +0200 (CEST),
[email protected] wrote:

Hi Everybody,
I am using USRP
with daugherboard of range 1MHz to 250MHz. I am running
the program
with gnu-radio 3.6.0 on Ubuntu 11.10. I am trying to run the
basic fm
receiver program as shown in the video.

http://www.youtube.com/watch?v=KWeY2yqwVA0 [1]

Whenever I try to
execute the code, I get following things on grc. I have
double checked
that the daughterboard works for the range. When I see the
fft plot of
the received signal I see that I have just noise all around.
The
hardware does not support the requested RX frequency:
Target
frequency: 100.000000 MHz
Actual frequency: -28.000000 MHz

aUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaU

I have also tried to see if the antenna choices are correct. I
checked it
with uhd_usrp_probe
The important part of the result
was
RX Subdev: AB
| | | | Name: Basic RX (0x0001) - AB
| | | |
Antennas:
| | | | Sensors:
| | | | Freq range: -250.000 to 250.000
Mhz
| | | | Gain Elements: None
| | | | Connection Type: IQ
| | |
| Uses LO offset: No
| | |


| | | /
| | |
| RX Subdev: BA
| | | | Name: Basic RX (0x0001) - BA
| | | |
Antennas:
| | | | Sensors:
| | | | Freq range: -250.000 to 250.000
Mhz
| | | | Gain Elements: None
| | | | Connection Type: QI
| | |
| Uses LO offset: No

So, when I try to work with uhd_fft. I got
same problem with following
results
uhd_fft --spec B:AB

linux;
GNU C++ version 4.6.1; Boost_104601; UHD_003.004.001-39-unstable


Opening a USRP1 device…
– Using FPGA clock rate of
64.000000MHz…
Using Volk machine: ssse3_64

UHD Warning:
The
hardware does not support the requested RX frequency:
Target
frequency: 100.000000 MHz
Actual frequency: -28.000000 MHz

Could
you help me out here?
Thanks in advance.

– Pranav Sakulkar


Discuss-gnuradio
mailing list
[email protected] [2]

https://lists.gnu.org/mailman/listinfo/discuss-gnuradio [3]

The aU is
because your audio subsystem is experiencing underruns, probably because
you have a sample-rate issue in your flow-graph.

The UHD warning is
because the BASIC_RX has no downconversion hardware at all, which means
that any frequency above Nyquist (32Mhz for USRP1 and 50Mhz for N2XX)
requires that the FPGA/ADCs sample the appropriate alias frequency, and
UHD is warning you that’s what it’s doing. But without analog filtering
in the front-end, you’ll end up with unwanted aliases as well. The
BASIC_RX is very “BASIC”, and it’s really intended as an interface card
to “proper” RF front-ends, with filtering, and probably downconversion
to an IF.

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