# Unmodulated carrier transmitted after stopping GR/PF model
**URL:** https://discourse.myriadrf.org/t/unmodulated-carrier-transmitted-after-stopping-gr-pf-model/4099
**Category:** LimeSDR
**Created:** [30 January 2019 22:08 UTC](https://discourse.myriadrf.org/t/unmodulated-carrier-transmitted-after-stopping-gr-pf-model/4099 "2019-01-30T22:08:21Z")
**Posts on this page:** 5
**Page:** 1
### Author:  [@TehWan](https://discourse.myriadrf.org/u/TehWan)
#### Post date: [30 January 2019 22:08 UTC](https://discourse.myriadrf.org/t/unmodulated-carrier-transmitted-after-stopping-gr-pf-model/4099/1 "2019-01-30T22:08:21Z")
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.
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.
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### Author:  [@andrewback](https://discourse.myriadrf.org/u/andrewback)
#### Post date: [31 January 2019 06:10 UTC](https://discourse.myriadrf.org/t/unmodulated-carrier-transmitted-after-stopping-gr-pf-model/4099/2 "2019-01-31T06:10:12Z")
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?
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### Author:  [@ccsh](https://discourse.myriadrf.org/u/ccsh)
#### Post date: [31 January 2019 08:25 UTC](https://discourse.myriadrf.org/t/unmodulated-carrier-transmitted-after-stopping-gr-pf-model/4099/3 "2019-01-31T08:25:07Z")
I don’t think this is something recent, have seen that since the beginning (but I was working mostly with SoapySDR + UHD).
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### Author:  [@gasparka](https://discourse.myriadrf.org/u/gasparka)
#### Post date: [31 January 2019 09:39 UTC](https://discourse.myriadrf.org/t/unmodulated-carrier-transmitted-after-stopping-gr-pf-model/4099/4 "2019-01-31T09:39:29Z")
+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.
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### Author:  [@TehWan](https://discourse.myriadrf.org/u/TehWan)
#### Post date: [31 January 2019 19:08 UTC](https://discourse.myriadrf.org/t/unmodulated-carrier-transmitted-after-stopping-gr-pf-model/4099/5 "2019-01-31T19:08:12Z")
Yes, I am using gr-limesdr blocks.