Hi all
As a newbie at gnuradio, currently I have two problems. I want to transmit an audio file with gmsk modulation. I used the below transmitter and receiver flow graphs which include packet encoder/decoder blocks. It works but the audio I hear is "like" that it is playing 10x faster than normal that it gets intermittent too much and sound card can't follow it! I couldn't find why. Can you please tell me what i have missed here?
Can the packet encoder/decoder be the cause?
I guessed maybe the packet encoder/decoder are the sources of problem (because seemingly they are obsolete). Therefore I tried to implement what these two blocks do. I reached at the loopback configuration below in which I packed the data going into modulator. But it does not work. no warning no error but nothing to hear either! then I removed the mod/demod combination and put a tag gate block. This time it was ok as expected of course. This shows something is wrong with the mod/demod. I couldn't figure it out and this is now my second problem. Please guide me to the right way.
The format object I used is: digital.header_format_default(digital.packet_utils.default_access_code, 0)
and the endianness of repack bits block is MSB with length tag key of packet_len.
I'm using Ettus B205 SDR boards on Ubuntu 18.04 and GRC 3.7.13.4.
Thank you in advance.
--
Amir Hossein Aalipour
MSc student of Electronics engineering
Department of Electrical Engineering
Sharif University of Technology
transmiiter.png
receiver.png
loopback.png
loopback.grc