Basic boards's problem with benchmark_tx.py/benchmark_rx.py

hello,everyone!

I have tested my usrp boards Basic Tx/Basic Rx, and run the following
commands:
Basic Tx: python benchmark_tx.py -f 100M
Basic Rx: python benchmark_rx.py -f 100M

It seemed that both sides send or receive ok spearately, but there is
no link constructed between them, and I have tried it with different
kinds of antenna but all couldn’t receive properly, so does anyone know
the reason and what could be?

BTW, I have successfully test daughterboards RFX2400 within the same
scene and the same program, just work in different frequency,but one
success and the other failure.