Piotr, This is especially baffling to me, because I recall that the SKY13335-187LF switches used in B210 must be isolated from DC on all RF ports. But they are! The only components connected to the SMA connectors are a series 470pF capacitor.
Perhaps the problem is exacerbated by poor impedance matching rather than by lack of a DC path. If reflected power was causing the problem I'd expect lowering the transmit gain to affect your results. Could you try that for me? Nick On Fri, Oct 6, 2017, 1:41 AM Piotr Krysik via USRP-users < [email protected]> wrote: > W dniu 27.09.2017 o 07:06, Piotr Krysik via USRP-users pisze: > > Hi all, > > > > I narrowed down when the issue occurs. > > > > When using separate sides of B210 for transmitting (i.e. TX/RX port on > > RF A side) and receiving (i.e. RX2 port on RF B side) everything is fine > and B210 starts transmitting like i.e. X310. > > > > > > The problem appears when transmitting and receiving on the same side of > > B210 and it is dependent on what you connect to the TX port. The 300us > > transition appears if I don't connect anything and measure the TX-RX > > leakage or when VERT900 antenna from Ettus is connected. > > > > I tried also to connect a power splitter to the TX port and an antenna > > to one of the splitter's ports - with the same result. But as soon as I > > connected the 30dB attenuator to another port of the splitter, the > > problem immediately goes away. > > > >> The attenuator also has a path (resistive 50 ohms) to ground....an > >> antenna with a small pad on it (say 1 db) will probably work fine as > well. > >> Kent Torell > > So you might be right here Kent that it was the path to the ground in > the attenuator that > > changed how the output behaves. It is funny thought that the problem > > only appears when RX2 port on the same side of B210 is also used :). > > > Hi all, > > As for my current application transmitting bursts and receiving > continuous signal with use of all B210 RF ports is not required, I can > avoid the problem. So I don't have currently motivation to pursue the > investigation further. > > The problem isn't solved though. There are of course applications in > which it is required to use all RX and TX ports and it is convenient to > transmit burst. If someone needs it I can provide the codes that I used > for tests (they are not secret, I just don't want to lose time on > preparing them in case there is no such person). What I have is a GNU > Radio block that adds tx_time and length tags to a signal, with user > defined burst length and gap length. From the tagged stream UHD sink is > able to produce bursts instead of continuous signal. I have also a GRC > application that presents the problem. > > Best Regards, > Piotr Krysik > > _______________________________________________ > USRP-users mailing list > [email protected] > http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com >
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