Have a rtl-sdr (or other SDR receiver) and wish it were a transceiver (transmit/receive)?
Have a Raspberry Pi?
How about a wire (any wire will do)?
Well now you can transmit along with receiving!
RPITX Allows you to use a single GPIO pin for transmitting various radio modulation.
This means voice, data, FM/AM.
See the demonstration here: https://tube.tchncs.de/videos/watch/5b718866-07e8-48a1-ae64-05797d9efb63
I will be doing tutorials on the complete setup for transmitting your own radio in coming videos, along with taking a closer look inside RPITX to see how viable the idea is (porting to a board I recently received- it might workout, might not).