Thanks for the reply, Jason. The uhd_usrp_probe --version command gave the following result:
linux; GNU C++ version 4.4.5; Boost_104200; UHD_003.004.000-71810ad 003.004.000-71810ad Do I have to download the latest UHD image? The image that I am using right now was downloaded by one of my colleagues and I think that he did it recently. Also, I tried running the benchmark_tx and benchmark_rx codes with a 1 MHz frequency offset input, i.e., I gave the following commands: ./benchmark_tx.py -f 2.4G -r 1M -m gmsk -a "addr = 192.168.10.2" ./benchmark_tx.py -f 2.401G -r 1M -m gmsk -a "addr = 192.168.10.2" Since the uhd_fft.py and the my lab spectrum analyzer show a 1 MHz frequency offset, I assumed that the above commands would work. Unfortunately, this did not help either! Suggestions will be very appreciated. Thanks, Nazmul On Wed, Feb 8, 2012 at 7:37 PM, Jason Abele <ja...@ettus.com> wrote: > On Wed, Feb 08, 2012 at 06:39:24PM -0500, Nazmul Islam wrote: > > Hello, > > > > I am running the benchmark_tx.py codes and looking at the spectrum of the > > signals using uhd_fft.py. I am using the latest image of GNU radio > > (GNUradio 3.5) and I have XCVR2450 daughterboards. I ran the > > benchmark_tx.py code in three transmitter nodes and surprisingly, all of > > them are transmitting with 1 MHz frequency offset! I have attached two > > screenshots with the email (I hope that they go through). I give the > > following input parameters to run the benchmark_tx code. > > > > ./benchmark_tx.py -f 2.4G -r 1M -m gmsk -M 10 -a "addr = 192.168.10.2" > > > > Both uhd_fft.py and the spectrum analyzer of my laboratory show that the > > received signal is centered at 2.401 GHz. I varied the frequency to 2.45 > > GHz, 2.41 GHz, but this 1 MHz frequency shift persists. > > > > When I run the benchmark_rx.py code at the receiver nodes, they don't > > receive/detect any packets (due to the frequency offset, I guess). I even > > tried to run the transmitter at 2.4 GHz and the receiver at 2.401 GHz. > > However, that did not help either! > > > > I will try to modify the control loop gain parameters using Tom's blogs > > suggestions and see if that helps. However, I am really surprised to see > > how all three different transmitter nodes can transmit with almost > exactly > > 1 MHz frequency offset. Any suggestion will be appreciated. > > > > Can you tell us which version of UHD you are using? > (uhd_usrp_probe --version) > > We have heard reports of such an issue and my best guess is that it was > related to an accidental swap of I and Q in the XCVR2450 transmitter > code. This went in after the 3.3.2 release and is fixed on latest UHD > master since 837437c65ce36d418cceb3df5b093f9497b3af5f > > Jason > -- Muhammad Nazmul Islam Graduate Student Electrical & Computer Engineering Wireless Information & Networking Laboratory Rutgers, USA.
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