Transmitting on both channels with the LFTX board

Hello,

I have a LFTX board and a LFRX board in a USRP-N210 and I am using GRC
3.6.1 in ubuntu 13.10.

I would like to transmit on both LFTX channels simultaneously. Does
anyone
know how?

Here are some things I tried:

I can transmit on either channel by specifying the subdevice as A:A or
A:B
in the attached file called TransmitsOneChannel.grc.

If I try to do this on both channels it does not work. (See
DoesNotWork.grc) When I run the program it just starts, stops, and the
python output on the bottom of GRC just says ‘done’.

I would like to specify two sources on the sink like in
(StillDoesNotWork.grc) but it complains that there are not two tx dsp’s.
It
would be nice if I could specify the input type as ‘float’ but that does
not seem to be an option.

However if I choose the subdevice A:AB I can get both channels to
transmit
but I cannot seem to control what they send. My attempt is in
TransmitsBothChannelsButWeird.grc where I specify the real and imaginary
parts of the signal to the USRP by feeding float signal sources into a
float to complex conversion block. The scope output within GRC looks
right
but when I use an oscilloscope on the actual outputs, the sine wave
output
seems to flip around randomly in phase and amplitude. It looks the same
on
both channels…

Any help would be appreciated,
Karl Edler