Unmodulated carrier transmitted after stopping GR/PF model

Projects LimeSDR
1

I tried several different GNU Radio and Pothos Flow models. Whenever I stop the model, my LimeSDR-USB begins transmitting an unmodulated carrier on its last center frequency with the previously used TX gain.

Here’s a screenshot using my RTL-SDR as a monitor.

image
image.png960×1040 97 KB

I have not figured out a way to make it stop transmitting other than unplugging it (obviously), setting the TX gain to the minimum (so it’s drowned out by noise, but technically still transmitting), or powering down the TX modules (which is unwanted as I’d have to power it back on to run my model).

Thanks.

2

Are you using the gr-limesdr blocks?

@IgnasJ, could this be related to a recent commit I saw that destroys the stream upon closing a flowgraph?

3

I don’t think this is something recent, have seen that since the beginning (but I was working mostly with SoapySDR + UHD).

4

+1, this was/is even present on BladeRF (LMS6 chip).

Two ideas:

  1. DAC gets stuck at outputting the last value.
  2. Analog DC correction is not turned off properly i.e. it keeps adding constant voltage to output.
5

Yes, I am using gr-limesdr blocks.