[Discuss-gnuradio] Simplex RX/TX on USRP with GRC (RX/TX port of a B200mini)

[Martijn Moeling]

Hi All,

I just finished searching this lists archives for some more information on how 
to make a simplex radio with my USRP B200mini and GRC.
I am a ham radio operator and would like to learn from building stuff that 
replaced my radio’s.

I have had some success with transmitting and receiving and on the USRP 
mailinglist I was pointed towards using "stream tags” to implement a simple 
NBFM transceiver but after playing with it I just cannot seem to find out how 
to do it.

When searching the net I find tons of RTL-SDR receive stuff but I bought an 
B200mini to send! At the end I will use GPIO, pindiode switches and relays to 
build a all-band, all-mode setup.


Can someone help me out on how to switch the TX/RX port in grc in a proper way?

Some information:

for now I use the internal microphone in my Mac as the audio source,
and the speakers for the output.

I will probably need a USRP source and sink and want to use a on screen button 
to switch between RX and TX (like a PTT button)

for now I do not bother using a PA, implementing that will be no real issue. I 
have a local NBFM repeater which I can work with the standard output power from 
the USRP.
I managed to create a transmitter with CTCSS to open the repeater and in the 
same flow chart I have a second flow graph to receive.

It all works if I completely disable either the RX or TX chain and run it. I 
just need some way to switch between the two during runtime and in a proper 
fashion.

Kind regards,

Martijn