Greetings Vladislav Unfortunately these block functions are not represented in terms of GRC blocks. You're correct that dv_tx.py is at present the only implementation (aside from its big brother, multi_tx.py) Also AFAIK the rtl-sdr is a receive only device - it's not usable for transmitting.  Don't know about the limesdr... Max On Monday, January 20, 2020, 11:46:01 AM EST, Владислав Д. <quasar1902(a)gmail.com> wrote: Good evening, Would You kindly to answer a few questions about the OP25 project and how to organize a transmitter with it using SDR devices (RTL-SDR, LimeSDR)?In the creation process of DMR-standard transmitter in the GnuRadio environment, we came across the absence of some necessary blocks: 4FSK modulator, DMR encoder, packet shaper.Inside the OP25 project we found a file that contains some functionality of DMR TX (dv_tx.py), but only in form of code, not as a GRC block. Could you tell us does this file fully implements the TX-side of the DMR system and whether there is an analogue of it, in the form of a GRC block for GnuRadio? We will be very grateful if you can help us sort this out. Yours faithfully, Vladislav.