lol... so obvious, that i overlooked this option. however, for now we now at least, that this is not implemented int gqrx. i thought, that it would be a device argument.
but, you're right, in gr you can't use channel 1 without using channel 0, at least with the osmocom blocks. maybe some day there will be a soapy-source & -sink
i already tried uhd blocks in gr with the lime, without any success. i get some version missmatch and i don't want to recompile everything to break it in the end ;D at least it is working
edit: actually you could set the antenna of channel 0 to 'NONE', which is possible and just use channel 1 then. i believe, that this would consume usb bandwidth though...
RX Antennas: NONE, LNAH, LNAL, LNAW, LB1, LB2
TX Antennas: NONE, BAND1, BAND2
i guess, you'd have to use a null sink then for the 0th output of the block then, but at least we have workaround for now