USRP N200, RFX 1800 not receiving signal

Hi,

My USRP N200 / RFX 1800 combination seems to not receive any useful
signal. The software seems to work, there are no error messages, and the
USRP seems to sample noise but does not even show a signal from a signal
generator.

Has anybody an idea what I might be doing wrong, or what else I could
try?

I use Ubuntu and installed/compiled the latest GNUradio / UHD software.
I used the uhd_fft.py script to test the radio. I tried different
frequencies, both antennas and different transmit power level on the
signal generator (-110dBm - -10dBm). The only thing I see is noise,
which changes slightly when I change the gain.

The command to start uhd_fft.py was:

uhd_fft.py -A RX2 -f 2G --samp-rate=16M

The output of uhd_usrp_probe is:


linux; GNU C++ version 4.4.3; Boost_104000; UHD_003.002.001-fd33faa

– Opening a USRP2/N-Series device…
– Current recv frame size: 1472 bytes
– Current send frame size: 1472 bytes


/
| Device: USRP2 / N-Series Device
| _____________________________________________________
| /
| | Mboard: USRP-N200
| | rev: 2560
| | mac-addr: a0:36:fa:26:30:30
| | ip-addr: 192.168.10.2
| | gpsdo: none
| | serial: E3R10Z0UN
| |
| | Time sources: none, external, external, mimo
| | Clock sources: internal, external, mimo
| | Sensors: mimo_locked, ref_locked
| | _____________________________________________________
| | /
| | | RX DSP: 0
| | | Freq range: -50.000 to 50.000 Mhz
| | _____________________________________________________
| | /
| | | RX DSP: 1
| | | Freq range: -50.000 to 50.000 Mhz
| | _____________________________________________________
| | /
| | | RX Dboard: A
| | | ID: RFX1800 (0x0034)
| | | _____________________________________________________
| | | /
| | | | RX Subdev: 0
| | | | Name: RFX1800 (0x0034)
| | | | Antennas: TX/RX, RX2
| | | | Sensors: lo_locked, rssi
| | | | Freq range: 1500.000 to 2100.000 Mhz
| | | | Gain range PGA0: 0.0 to 70.0 step 0.0 dB
| | | | Connection Type: QI
| | | | Uses LO offset: No
| | | _____________________________________________________
| | | /
| | | | RX Codec: A
| | | | Name: ads62p44
| | | | Gain range digital: 0.0 to 6.0 step 0.5 dB
| | | | Gain range fine: 0.0 to 0.5 step 0.1 dB
| | _____________________________________________________
| | /
| | | TX DSP: 0
| | | Freq range: -250.000 to 250.000 Mhz
| | _____________________________________________________
| | /
| | | TX Dboard: A
| | | ID: RFX1800 (0x0035)
| | | _____________________________________________________
| | | /
| | | | TX Subdev: 0
| | | | Name: RFX1800 (0x0035)
| | | | Antennas: TX/RX
| | | | Sensors: lo_locked
| | | | Freq range: 1500.000 to 2100.000 Mhz
| | | | Gain Elements: None
| | | | Connection Type: IQ
| | | | Uses LO offset: Yes
| | | _____________________________________________________
| | | /
| | | | TX Codec: A
| | | | Name: ad9777
| | | | Gain Elements: None

On 24/08/2011 9:41 AM, Urs Hunkeler wrote:

I use Ubuntu and installed/compiled the latest GNUradio / UHD
software. I used the uhd_fft.py script to test the radio. I tried
different frequencies, both antennas and different transmit power
level on the signal generator (-110dBm - -10dBm). The only thing I see
is noise, which changes slightly when I change the gain.

The command to start uhd_fft.py was:

uhd_fft.py -A RX2 -f 2G --samp-rate=16M

Since 16M isn’t a “proper” sample rate for a N200, perhaps that’s the
problem.

Try 1.0M, 2.0M, 2.5M, 5.0M, 10M

If it’s just a narrowband signal, you don’t need very much host-side
bandwidth.

On 24/08/2011 12:20 PM, Urs Hunkeler wrote:

Urs
Yes, the driver will “adjust”, but then your signals may not appear
where you expect them to be.

Hi Marcus,

That’s right. Based on a discussion with Jason it looks like there might
be a hardware problem. I have a tendency to always blame software first
:-). Thanks for your tips.

Cheers,
Urs

On 8/24/11 6:22 PM, Marcus D. Leech wrote:

Cheers,
Urs
Yes, the driver will “adjust”, but then your signals may not appear
where you expect them to be.

Ok, but there was absolutely no spike and the signal did not change when
I disconnected the cable or toggled the RF TX button on the signal
generator…