Re: [Discuss-gnuradio] Transmitting bursts with GRC by inserting SOB and EOB

[Frederik Wing]

> > > > > - You're using an ancient UHD version. Is there a reason you can't
> > > > > >>>>use a
> > > > > >>>>newer one?
> > > > >>>I am using Ubuntu 14.04 LTS and just pulled GNU Radio and UHD from the
> > > > >>>packet sources. There is no newer version available. And I don't
> > > > >>>like to
> > > > >>>compile myself unless it is absolutely necessary.
> > > >>Consider it outdated. Ubuntu's packet sources are most of the time
> > > >>horribly out of pace compared to GNU Radio's development process.
> > > >>For UHD it's the same. Note that Ettus ships its own Ubuntu packages
> > > >>for UHD*and*  GNU Radio, so you can get a non-ancient version of both
> > > >>without even compiling it.
> > > >>By the way: GNU Radio is a software radio developer's framework. You
> > > >>can do great things with it without touching a compiler, but at many
> > > >>points it becomes helpful when one can write his own C++ block, so
> > > >>you definitely need to lose your fear of compilers if you want to use
> > > >>GNU Radio to its fullest potential:)
> > >
> > >After some hours of compiling time I could finally update GNU Radio to
> > >version 3.7.6 and UHD to 003.008.
> > >
> > > > >>>I don't think it's because of an outdated version of UHD as the
> > > > >>>"tags_demo" application is working perfectly with my current version.
> > > >>... Well, my old tube radio also still works;)
> > >
> > >Unfortunately, even with the newest version the USRP is still
> > >transmitting its carrier over the air. I tried both with the Message
> > >Burst Source as well as with the Stream to Tagged Stream Block
> > >combined with setting a Length Tag name in the USRP Sink. With the Tag
> > >Debug Block I see tx_sob+tx_eob and the Length Tag, respectively. They
> > >all seem to be at the right place and have the right value.
> :(  ok, so we see something that looks like significant LO leakage.
>
> You can use offset tuning, by specifying a tune request instead of
> simply a target frequency f_t. By doing so, you instruct the USRP to
> tune the oscillator of the daughterboard to some frequency f_LO, and let
> the FPGA shift the resulting signal to baseband by a second frequency
> f_FPGA, so that f_LO+f_FPGA = f_t.
>
> You thereby would move the LO leakage out of your desired signal. Would
> that help you?

Thanks for this suggestion. It would be a workaround to the actual 
problem. And if there is no other way I have to do so.

I cannot believe that there is no solution to it since the "tags_demo" 
application shows that it is indeed possible. :-/

Frederik.