[Discuss-gnuradio] some problem about benchmark_tx & benchmark_rx

hello all

i am using the example of /gr-digital/examples/narrowbands

the benchmark_tx.py and the benchmark_rx.py ,and my devices are two B210

these is my command:

sudo ./benchmark_tx.py -f 175e6 -m bpsk --bitrate 500e3 --tx-gain 60

another computer

sudo ./benchmark_rx.py -f 175e6 -m bpsk --bitrate 500e3 --rx-gain 30

and the result is if i start the rx at first ,then start the tx ,the rx will recieve nothing ,

if i start the tx at first,then start the rx when the tx is running,the rx program will recieve the data,

is there someone meet the same problem?and why i start the rx at first then start the tx, the program will recieve nothing(this means no output in command line)?

thank you

--Ekko