[Discuss-gnuradio] UHD half bandwidth on USRP1 ?

[Vincenzo Pellegrini]

Hi List,

As I'm now fully moving to UHD, I've been trying for a while to do:

./tx_samples_from_file --freq 809500000 --rate 8e6 --file /home/vincenzo/Desktop/OFDM_DUMP --type short --bw 8 --subdev A:0 --gain 25

with a USRP1,

expecting my OFDM file to be transmitted over the requested 8MHz @ 8 complex Msps bandwidth like it always used to happen
when doing the same with the legacy libusrp.

unfortunately, although the executable output appears to confirm that the parameters I've requested have been correctly set,
 on the the spectrum analyser I'm seeing a correct OFDM shape downscaled to a 4 MHz bandwidth.

If I reduce the requested rate to 4 Msps, the shape is again correct but downscaled to 2 MHz bandwidth (instead of the 4 MHz that I would be expecting in this case), and so on, getting all the time half the bandwidth I expect.

also the USRP 1 carrier peak (using RFX900) is at half the distance from my center frequency than it is when using libusrp instead.

has anybody experienced the same ? 
what am I getting wrong in the tx_samples_from_file example usage or UHD usage?

best regards to everybody

vincenzo

_______________BEGIN SCREENDUMP:______________________________

Creating the usrp device with: ...
-- Opening a USRP1 device...
-- Using FPGA clock rate of 64.000000MHz...
UACTUAL USRP Master Clock: 6.4e+07
WARNING !!! TEST VERSION
 ...Using Device: Single USRP:
  Device: USRP1 Device
  Mboard 0: USRP1 (Classic)
  RX Channel: 0
    RX DSP: 0
    RX Dboard: B
    RX Subdev: WBX RX v2 + Simple GDB
  TX Channel: 0
    TX DSP: 0
    TX Dboard: A
    TX Subdev: RFX TX

Setting TX Rate: 8.000000 Msps...
Actual TX Rate: 8.000000 Msps...

Setting TX Freq: 809.500000 MHz...
Actual TX Freq: 809.500000 MHz...

Setting TX Gain: 25.000000 dB...
Actual TX Gain: 0.000000 dB...

Setting TX Bandwidth: 8.000000 MHz...
Actual TX Bandwidth: 8.000000 MHz...

Checking TX: LO: locked ...


  


-- 
Vincenzo Pellegrini
http://www.youtube.com/user/wwvince1