[Discuss-gnuradio] Large FFTs
We are considering to purchase a USRP2 + a DBSRX board in order to utilize it for some GPS stuff. Thus it would be interesting to know what's the maximum supported (implemented) FFTs size. I have checked the old discussions, but there's nothing really conclusive. What we are looking for is something larger than 16K FFT points. Maybe someone has experiences with such large FFTs and how they perform (Flops or FFTs per second)? Best regards, Thomas Hobiger -- ** Dr. Thomas Hobiger Space-Time Measurement Project Space-Time Standards Group New Generation Network Research Center National Institute of Information and Communications Technology -- 4-2-1 Nukui-Kitamachi, Koganei 184-8795 Tokyo Japan -- email: hobi...@nict.go.jp -- homepage (priv.): http://www.hobiger.org ** ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
RE: [Discuss-gnuradio] doubt about the the DC offset
hi Eric: I think I am the one who ask the same question in my last e-mail.But there is no answer for it.I still can not find where is the process of setting this value.and I do not understand why this value is 4M.I hope someone can help me to figure it out. thank you Date: Sun, 22 Aug 2010 20:16:30 -0700 From: e...@comsec.com To: tianxia...@hotmail.com CC: discuss-gnuradio@gnu.org Subject: Re: [Discuss-gnuradio] doubt about the the DC offset On Mon, Aug 23, 2010 at 09:42:56AM +0800, intermilan wrote: Hi all: when I run the test program test_usrp_standard_tx/rx.cc, I found that the DC offect is set to 4M. So can anyone tell me how this value come out and where can I find the process of setting this value? and can we set other values to instead of this value? Please search the mailing list archives. This questions was asked and answered in the last 10 days or so... Eric ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
[Discuss-gnuradio] Re: usrp_probe fails with AttributeError: 'Param' object has no attribute 'get_input'
Hi Josh, On calling 'usrp2_probe'I am getting the exact same error as Jacinda. I am working with the USRP2 kit for the first time . On calling usrp2_fft.py a GUI is opened but nothing is displayed in it . Also , in the terminal window an error message is displayed saying usrp2: channel 0 not recieving usrp2:: rx_samples() failed I have installed only 1 version of gnuradio (gnuradio3.3.0) from their FTP . Kindly help. Himanshu ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Re: [Discuss-gnuradio] Large FFTs
Hi, Gnuradio uses FFTW, which as a pretty nice benchmark page [1]. If we look at the results for a fairly new intel processor, we see that a 262144 point FFT can be computed with about 9 GFLOPS speed, which means that a 262144 point FFT should be done in less than 3 ms. [1] http://www.fftw.org/speed/ I have been using 65 kpoint FFTs for real-time spectral analysis with USRP1 and USRP2 with no problems. juha On Mon, Aug 23, 2010 at 08:00, Thomas Hobiger hobi...@nict.go.jp wrote: We are considering to purchase a USRP2 + a DBSRX board in order to utilize it for some GPS stuff. Thus it would be interesting to know what's the maximum supported (implemented) FFTs size. I have checked the old discussions, but there's nothing really conclusive. What we are looking for is something larger than 16K FFT points. Maybe someone has experiences with such large FFTs and how they perform (Flops or FFTs per second)? Best regards, Thomas Hobiger -- ** Dr. Thomas Hobiger Space-Time Measurement Project Space-Time Standards Group New Generation Network Research Center National Institute of Information and Communications Technology -- 4-2-1 Nukui-Kitamachi, Koganei 184-8795 Tokyo Japan -- email: hobi...@nict.go.jp -- homepage (priv.): http://www.hobiger.org ** ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
[Discuss-gnuradio] semi OT - data-aided SNR estimate of a complex signal in MATLAB/Octave
I'm working on processing, in MATLAB/Octave, some data that I've taken with a communication device we've built. We're planning on moving to USRP/GNURadio, but before that happens, I've got to get this data processed. Previously we've done communication with an on-off-keying signal (OOK with a laser). We wanted to estimate the SNR of the signal, so we use a data-aided approach. Now I'm changing the system to use complex signaling and I'm struggling with how to do the SNR estimation with complex signals. Previously, we did this: Y=2*(RxSymbols-mean(RxSymbols)); % First statistic, E(Yi^2) Stat1=var(Y); % Second statistic, E(Yi*Xi) Stat2=mean(Y.*X); % SNR = 2*E(Yi*Xi)^2/( E(Yi^2)-E(Yi*Xi)^2 ) SNRlin=2*Stat2^2/(Stat1-Stat2^2); SNR_dB=10*log10(SNRlin); Now I need to modify this for complex signals. Should I: a) compute the SNR for the real and imaginary components separately and then somehow combine them? b) compute the SNR on the complex signals directly. If a), then how should I combine them? It's AWGN noise, btw. If b), then I need to take the covariance of Y, but I don't know how to take the two variances and use them. I've never been all that good at this stuff and I'm learning slowly. Thanks for your help. -William ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
[Discuss-gnuradio] (WBX+USRP) Unknown signal at the middle of any FFT plot in receive mode
Hello, I am currently testing two USRP radios with 3 WBX transcievers. When I test the receive path, I would use gnuradio companion and go from USRP source to FFT plot. However, I see that at every center frequency of the FFT window there is a signal even though I am not inputting anything. The signal power is about 0 dBm. Also, if I inject a signal, the power of the signal is shown to be much higher than the true power I am sending through. For example, when I send a -50 dBm signal it shows up to be +30 dBm and I've tried using multiple signal generators. So now I'm stuck. How do I fix this? Thank you. ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Re: [Discuss-gnuradio] (WBX+USRP) Unknown signal at the middle of any FFT plot in receive mode
On 08/23/2010 01:11 PM, jan acosta wrote: Hello, I am currently testing two USRP radios with 3 WBX transcievers. When I test the receive path, I would use gnuradio companion and go from USRP source to FFT plot. However, I see that at every center frequency of the FFT window there is a signal even though I am not inputting anything. The signal power is about 0 dBm. Also, if I inject a signal, the power of the signal is shown to be much higher than the true power I am sending through. For example, when I send a -50 dBm signal it shows up to be +30 dBm and I've tried using multiple signal generators. So now I'm stuck. How do I fix this? Thank you. The FFT plot in Gnu Radio is *uncalibrated*--it's showing you *relative power* and *NOT* dBm You *could* perform some calibration and apply calibration constants to the output of the FFT to turn it into dBm, but out of the box, it *is not* dBm. It's rather hard to make it be dBm, as well, since each daughtercard type is different, etc, etc. So, that signal at 0dB is actually quite small compared to your -50dBm input signal. it's an artefact of the down-conversion process. -- Marcus Leech Principal Investigator Shirleys Bay Radio Astronomy Consortium http://www.sbrac.org ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Re: [Discuss-gnuradio] USRP/gnuradio Issues in OS X
Hi Mark - I don't know where to point you exactly, since some tests work for you while others don't. You're using --with-fusb- tech=libusb1, which should work but hasn't been thoroughly tested (at least on OSX). Have you tried configuring without this flag then re- testing to see what happens? The native FUSB/OSX drivers do use the legacy libusb (as found on MacPorts), but they are well tested just as fast as those provided by libusb1. - MLD ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Re: [Discuss-gnuradio] USRP/gnuradio Issues in OS X
On Aug 23, 2010, at 11:52 AM, Michael Dickens wrote: Hi Mark - I don't know where to point you exactly, since some tests work for you while others don't. You're using --with-fusb-tech=libusb1, which should work but hasn't been thoroughly tested (at least on OSX). Have you tried configuring without this flag then re-testing to see what happens? The native FUSB/OSX drivers do use the legacy libusb (as found on MacPorts), but they are well tested just as fast as those provided by libusb1. - MLD I have the lib...@1.0.8 port installed rather than the libusb-leg...@0.1.12 port, because (I think) I have other stuff that wants the newer libusb port. I discovered that I needed to use the --with-fusb-tech=libusb1 flag to get the configure script to properly identify my libusb version. Before I used that flag everything would compile, but the usrp executables would fail to find a symbol they needed in libusb and then crash. -- Mark J. Blair, NF6X n...@nf6x.net Web page: http://www.nf6x.net/ GnuPG public key available from my web page. ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Re: [Discuss-gnuradio] USRP/gnuradio Issues in OS X
Hi Mary - So long as you use MacPorts for background dependencies, libusb1 and libusb-legacy (v0.1.12) can be installed at the same time you can easily choose between them (different PKGCONFIG files). Do note that libusb-compat does NOT work with FUSB/Darwin since GNU Radio's FUSB/LIBUSB code uses internals that are not in the 'compat' version (only the API is compat, not the internal implementation). On my MacBook Pro (10.5.8, i386), GNU Radio compiles and executes just fine using libusb-legacy -- so, if you're having issues using it let me know I'll see what I can do to help out. That said, I've also used libusb1 with some success -- so, you might have some other issue (e.g., a bad USB cable). - MLD On Aug 23, 2010, at 3:00 PM, Mark J. Blair wrote: I have the lib...@1.0.8 port installed rather than the libusb-leg...@0.1.12 port, because (I think) I have other stuff that wants the newer libusb port. I discovered that I needed to use the --with-fusb- tech=libusb1 flag to get the configure script to properly identify my libusb version. Before I used that flag everything would compile, but the usrp executables would fail to find a symbol they needed in libusb and then crash. ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Re: [Discuss-gnuradio] USRP/gnuradio Issues in OS X
On Aug 23, 2010, at 12:09 PM, Michael Dickens wrote: Hi Mary - So long as you use MacPorts for background dependencies, libusb1 and libusb-legacy (v0.1.12) can be installed at the same time you can easily choose between them (different PKGCONFIG files). Do note that libusb-compat does NOT work with FUSB/Darwin since GNU Radio's FUSB/LIBUSB code uses internals that are not in the 'compat' version (only the API is compat, not the internal implementation). On my MacBook Pro (10.5.8, i386), GNU Radio compiles and executes just fine using libusb-legacy -- so, if you're having issues using it let me know I'll see what I can do to help out. That said, I've also used libusb1 with some success -- so, you might have some other issue (e.g., a bad USB cable). - MLD I'll give libusb-legacy a try tonight (I don't have my USRP with me at work today). I'm sure I don't have a cable problem since I can transmit and receive signals with my USRP. Thanks for the suggestions! -- Mark J. Blair, NF6X n...@nf6x.net Web page: http://www.nf6x.net/ GnuPG public key available from my web page. ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Re: [Discuss-gnuradio] doubt about the the DC offset
On Mon, Aug 23, 2010 at 05:18:58PM +0800, intermilan wrote: hi Eric: I think I am the one who ask the same question in my last e-mail.But there is no answer for it.I still can not find where is the process of setting this value.and I do not understand why this value is 4M.I hope someone can help me to figure it out. http://osdir.com/ml/discuss-gnuradio-gnu/2010-08/msg00122.html We picked a value that improved the performance of the test cases we looked at. You are free to pick another value if it works better for you, for whatever interpretation of better you like. Date: Sun, 22 Aug 2010 20:16:30 -0700 From: e...@comsec.com To: tianxia...@hotmail.com CC: discuss-gnuradio@gnu.org Subject: Re: [Discuss-gnuradio] doubt about the the DC offset On Mon, Aug 23, 2010 at 09:42:56AM +0800, intermilan wrote: Hi all: when I run the test program test_usrp_standard_tx/rx.cc, I found that the DC offect is set to 4M. So can anyone tell me how this value come out and where can I find the process of setting this value? and can we set other values to instead of this value? Please search the mailing list archives. This questions was asked and answered in the last 10 days or so... Eric ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Re: [Discuss-gnuradio] Large FFTs
Dear Thomas, we have found some problems when using USRP2+DBSRX for GPS due to phase noise. See details in http://www.ruby-forum.com/topic/213845 If someone have succeded on this, we would appreciate some hints to make it work. Our software GPS receiver was not able to track signals, while it run smoothly when using USRP1 + DBSRX without modification. Best regards, Carles Fernandez On Mon, Aug 23, 2010 at 10:00 AM, Thomas Hobiger hobi...@nict.go.jp wrote: We are considering to purchase a USRP2 + a DBSRX board in order to utilize it for some GPS stuff. Thus it would be interesting to know what's the maximum supported (implemented) FFTs size. I have checked the old discussions, but there's nothing really conclusive. What we are looking for is something larger than 16K FFT points. Maybe someone has experiences with such large FFTs and how they perform (Flops or FFTs per second)? Best regards, Thomas Hobiger -- ** Dr. Thomas Hobiger Space-Time Measurement Project Space-Time Standards Group New Generation Network Research Center National Institute of Information and Communications Technology -- 4-2-1 Nukui-Kitamachi, Koganei 184-8795 Tokyo Japan -- email: hobi...@nict.go.jp -- homepage (priv.): http://www.hobiger.org ** ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
[Discuss-gnuradio] USRP2+WBX full duplex doesn't receive
I'm trying to simultaneously transmit and receive with a USRP2 and WBX in a C++ command line tool. I'm using txrx_wbx_raw_eth_20100608.bin and u2_rev3-20100603.bin on the USRP2 and have tried GNU Radio version 3.3.0 and 3.3.1 on the Ubuntu 10.04 host. I have a spectrum analyzer on TX/RX and an antenna on RX2. Transmitting without receiving works fine, as does receiving without transmitting. If I attempt to do both at the same time, the receive thread gets stuck -- that is rx_samples doesn't call the rx_sample_handler so I never receive the data I'm after. The transmit thread keeps running and I can see the transmitted signal on the spectrum analyzer. I've set breakpoints in various places in the USRP2 host code and as near as I can tell, there are no packets being received (poll times out each time it's called in eth_buffer::rx_frames). What am I missing? Is full duplex supported using raw ethernet with the WBX? -Marc ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
[Discuss-gnuradio] FFT filters--still a problem with filter growth
I thought the problem with FFT filters growing after initial construction was gone in recent Gnu Radio, but it's back. I'm running the latest next branch, along with UHD. Create an FFT filter of length X. If the filter coefficients change at run time and the resulting length is longer than the initial X, the flow-graph seems to wedge (the previous failure mode for this caused it to dump core). If I change my code so that the initial filter size is as big as it will ever need to be, I don't get any problems. I have a tap generator for the FFT filter that produces filters whose lengths are powers of 2, to hopefully improve performance. But if the initial filter is (let's say) length 4096, and then dynamically changed to 8192 or 16384, etc, then the flow-graph seems to wedge. ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Re: [Discuss-gnuradio] Large FFTs
Hi Juha, Gnuradio uses FFTW, which as a pretty nice benchmark page [1]. If we look at the results for a fairly new intel processor, we see that a 262144 point FFT can be computed with about 9 GFLOPS speed, which means that a 262144 point FFT should be done in less than 3 ms. [1] http://www.fftw.org/speed/ I have been using 65 kpoint FFTs for real-time spectral analysis with USRP1 and USRP2 with no problems. Your reply is related to running the FFT on the CPU, right? Do you have any experience running it on the FPGA of the USRP1 or USRP2? Thomas ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Re: [Discuss-gnuradio] Large FFTs
Hi Carles, Thanks for the reply. That's a very helpful comment. we have found some problems when using USRP2+DBSRX for GPS due to phase noise. See details in http://www.ruby-forum.com/topic/213845 Once we have the components in the lab, I am going to play with them, having your comment on my check-list. If someone have succeded on this, we would appreciate some hints to make it work. Our software GPS receiver was not able to track signals, while it run smoothly when using USRP1 + DBSRX without modification. By tracking signals, do you mean that one of the receiver loops (DLL, PLL) lost lock or does it only prevent to extract the navigation bits? Best regards, Thomas Hobiger -- ** Dr. Thomas Hobiger Space-Time Measurement Project Space-Time Standards Group New Generation Network Research Center National Institute of Information and Communications Technology -- 4-2-1 Nukui-Kitamachi, Koganei 184-8795 Tokyo Japan -- email: hobi...@nict.go.jp -- homepage (priv.): http://www.hobiger.org ** ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Re: [Discuss-gnuradio] Large FFTs
On Tue, Aug 24, 2010 at 1:02 AM, Thomas Hobiger hobi...@nict.go.jp wrote: Hi Carles, Thanks for the reply. That's a very helpful comment. we have found some problems when using USRP2+DBSRX for GPS due to phase noise. See details in http://www.ruby-forum.com/topic/213845 Once we have the components in the lab, I am going to play with them, having your comment on my check-list. If someone have succeded on this, we would appreciate some hints to make it work. Our software GPS receiver was not able to track signals, while it run smoothly when using USRP1 + DBSRX without modification. By tracking signals, do you mean that one of the receiver loops (DLL, PLL) lost lock or does it only prevent to extract the navigation bits? I mean that the PLL lost lock after a few seconds, so we were able to extract only a few (and useless) navigation bits. We played with the filter loop, without success for the moment. We are quite confident in the software receiver, it works nice with other hardware configurations, and that is why we suspect that it could be a hardware issue. We will be working on this in the next month. I will let you know our advaces. Best regards, Carles Best regards, Thomas Hobiger -- ** Dr. Thomas Hobiger Space-Time Measurement Project Space-Time Standards Group New Generation Network Research Center National Institute of Information and Communications Technology -- 4-2-1 Nukui-Kitamachi, Koganei 184-8795 Tokyo Japan -- email: hobi...@nict.go.jp -- homepage (priv.): http://www.hobiger.org ** ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Re: [Discuss-gnuradio] USRP2+WBX full duplex doesn't receive
On Mon, Aug 23, 2010 at 1:41 PM, Marc Epard mep...@me.com wrote: I'm trying to simultaneously transmit and receive with a USRP2 and WBX in a C++ command line tool. I'm using txrx_wbx_raw_eth_20100608.bin and u2_rev3-20100603.bin on the USRP2 and have tried GNU Radio version 3.3.0 and 3.3.1 on the Ubuntu 10.04 host. I have a spectrum analyzer on TX/RX and an antenna on RX2. Transmitting without receiving works fine, as does receiving without transmitting. If I attempt to do both at the same time, the receive thread gets stuck -- that is rx_samples doesn't call the rx_sample_handler so I never receive the data I'm after. The transmit thread keeps running and I can see the transmitted signal on the spectrum analyzer. I've set breakpoints in various places in the USRP2 host code and as near as I can tell, there are no packets being received (poll times out each time it's called in eth_buffer::rx_frames). If you stop transmitting, does your RX sample stream then begin again? If so, it is because I think auto transmit switching is enabled by default with the WBX on the USRP2. I asked a question a while back as to whether or not the WBX has auto TR enabled or not by default, and how to change it, but I don't think I got an answer. Auto TR switching basically stops the RX stream while something is in your TX buffer. - George ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
[Discuss-gnuradio] Anne Kwong wants to stay in touch on LinkedIn
LinkedIn Anne Kwong requested to add you as a connection on LinkedIn: -- Abdul, I'd like to add you to my professional network on LinkedIn. - Anne Kwong Accept invitation from Anne Kwong http://www.linkedin.com/e/kcqq4e-gd86slvk-4v/vd6zfNxBgx85xjU-yrUbg0DbdNCYdgCBPTBioq/blk/I818830346_3/pmpxnSRJrSdvj4R5fnhv9ClRsDgZp6lQs6lzoQ5AomZIpn8_cRYSd3cMcPwUcjx9bR4PsnwVqlsNbPkVd3cUdPcVdj4LrCBxbOYWrSlI/EML_comm_afe/ View invitation from Anne Kwong http://www.linkedin.com/e/kcqq4e-gd86slvk-4v/vd6zfNxBgx85xjU-yrUbg0DbdNCYdgCBPTBioq/blk/I818830346_3/0PnPoQcP0Pe3wNe4ALqnpPbOYWrSlI/svi/ -- (c) 2010, LinkedIn Corporation___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
RE: [Discuss-gnuradio] doubt about the the DC offset
hi: So that mean you have done many test cases,then found the 4M is the best value to improve the performance.but there is another question,where do you set this value in the code? I can not find this in the code.I hope you can tell me the position of this value is set at 4M in the code. Thank you Date: Mon, 23 Aug 2010 12:35:41 -0700 From: e...@comsec.com To: tianxia...@hotmail.com CC: discuss-gnuradio@gnu.org Subject: Re: [Discuss-gnuradio] doubt about the the DC offset On Mon, Aug 23, 2010 at 05:18:58PM +0800, intermilan wrote: hi Eric: I think I am the one who ask the same question in my last e-mail.But there is no answer for it.I still can not find where is the process of setting this value.and I do not understand why this value is 4M.I hope someone can help me to figure it out. http://osdir.com/ml/discuss-gnuradio-gnu/2010-08/msg00122.html We picked a value that improved the performance of the test cases we looked at. You are free to pick another value if it works better for you, for whatever interpretation of better you like. Date: Sun, 22 Aug 2010 20:16:30 -0700 From: e...@comsec.com To: tianxia...@hotmail.com CC: discuss-gnuradio@gnu.org Subject: Re: [Discuss-gnuradio] doubt about the the DC offset On Mon, Aug 23, 2010 at 09:42:56AM +0800, intermilan wrote: Hi all: when I run the test program test_usrp_standard_tx/rx.cc, I found that the DC offect is set to 4M. So can anyone tell me how this value come out and where can I find the process of setting this value? and can we set other values to instead of this value? Please search the mailing list archives. This questions was asked and answered in the last 10 days or so... Eric ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Re: [Discuss-gnuradio] Large FFTs
Dear Carles, On Mon, 2010-08-23 at 21:37 +0200, Carles Fernandez wrote: Dear Thomas, we have found some problems when using USRP2+DBSRX for GPS due to phase noise. See details in http://www.ruby-forum.com/topic/213845 I have experimented with using the clock from the usrp to a modified TVRX (disabling the internal TVRX clock, using a 4 Mhz clock from the usrp). One of my findings was that if you use a low resistor from the usrp clock output to a daughterboard, followed by a relatively large capacitor to ground (for lowpass filtering) you can get a lot of spurious. The usrp can generate quite some power on this clockline. When you load the clockline to heavy, it wil start generating RF power. The load being a low resistor and big capacitor. The antenna being the track from the usrp to the lowpass filter. In the worst case you can be generating several milliwatts. This can definitely have an effect on the performance. Especially if you happen to be on a multiple of the daughterboard clock. My advise would be to experiment with a higher impedance lowpass filter which does not put a heavy load on the clockline. You could also experiment with a buffer amplifier. Good luck, Martin Dudok van Heel Olifantasia.com If someone have succeded on this, we would appreciate some hints to make it work. Our software GPS receiver was not able to track signals, while it run smoothly when using USRP1 + DBSRX without modification. Best regards, Carles Fernandez On Mon, Aug 23, 2010 at 10:00 AM, Thomas Hobiger hobi...@nict.go.jp wrote: We are considering to purchase a USRP2 + a DBSRX board in order to utilize it for some GPS stuff. Thus it would be interesting to know what's the maximum supported (implemented) FFTs size. I have checked the old discussions, but there's nothing really conclusive. What we are looking for is something larger than 16K FFT points. Maybe someone has experiences with such large FFTs and how they perform (Flops or FFTs per second)? Best regards, Thomas Hobiger -- ** Dr. Thomas Hobiger Space-Time Measurement Project Space-Time Standards Group New Generation Network Research Center National Institute of Information and Communications Technology -- 4-2-1 Nukui-Kitamachi, Koganei 184-8795 Tokyo Japan -- email: hobi...@nict.go.jp -- homepage (priv.): http://www.hobiger.org ** ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Re: [Discuss-gnuradio] Large FFTs
Hi Carles, I mean that the PLL lost lock after a few seconds, so we were able to extract only a few (and useless) navigation bits. We played with the filter loop, without success for the moment. We are quite confident in the software receiver, it works nice with other hardware configurations, and that is why we suspect that it could be a hardware issue. We will be working on this in the next month. I will let you know our advaces. Thanks. I am looking forward to have my USRP2 in the hands, to start playing with it. Your experience is highly appreciated. Best regards, Thomas -- ** Dr. Thomas Hobiger Space-Time Measurement Project Space-Time Standards Group New Generation Network Research Center National Institute of Information and Communications Technology -- 4-2-1 Nukui-Kitamachi, Koganei 184-8795 Tokyo Japan -- email: hobi...@nict.go.jp -- homepage (priv.): http://www.hobiger.org ** ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
