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jopohl / urh

Universal Radio Hacker: Investigate Wireless Protocols Like A Boss
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PlutoSDR - when transmittion is started the first thing transmitted is some junk #659

Closed Matjaz-B closed 5 years ago

Matjaz-B commented 5 years ago
Expected Behavior

Only actual signals should be transmitted

Actual Behavior

When starting transmission the first thing transmitted is some highpower noise. After that the actual data is transmitted. It seems like FIFO is not cleared and some obsolete data is transmitted before actual data.

Steps To Reproduce
  1. Open two URHs (or spectrum analyser)
  2. Use one URH as receiver
  3. Use one URH as transmitter - set transmitt buffer to all muted data
  4. Start transmission for 1s and stop if afterwards - repeat for few times
  5. On reception side you will see received peaks

Or - transmit data via command line: urh_cli.exe -d PlutoSDR -f 868000000.0 -s 3e6 -bb -20 -g -70 -cf 868000000.0 -mo FSK -bl 61 -p0=-50000.0 -p1=+50000.0 -m 555559999999999999999999999999999/10ms -tx --hex The issue is more visible, when gain is set to low value. The initial noise is quite wideband and amplitude is almost at 0 dBm.

Screenshots

urh_tx_issue

Platform Specifications
andynoack commented 5 years ago

Well, that is a behaviour we can observe with many SDRs when they change into transmit mode and we think that it is a hardware or driver problem. Can you test with another TX software (e.g. Gnuradio), if the problem occurs there too?

andynoack commented 5 years ago

Any news here? Can we close the Issue?

Matjaz-B commented 5 years ago

Thanks for response. I did not know that this is genral problem (SW and HW). Frankly before this use case I was always using higher output power (more than -50 dBm) where this behaviour was not important/detected. I will try to reproduce this issue with GNU Radio to locate the source of the problem. I hope that I'll something to show by end of this week.

Thanks

vsboost commented 5 years ago

I get the same with LimeSDR-mini - huge spike of junk at startup, prior to the signal being replayed even starts, also notice once i hit stop the mini still is in TX, have to go to receive a signal for it to stop the TX.

jopohl commented 5 years ago

Just verified with a very simple GNU Radio Flowgraph that the behaviour is also present there: image

Every time I run the flow graph I record a short signal as described in this issue.

Therefore, I assume this is a hardware and/or driver problem of PlutoSDR and we cannot do much about it at URH side.

jopohl commented 5 years ago

@vsboost just saw that this is an open issue with LimeSDR-mini: https://github.com/myriadrf/LimeSuite/issues/235

vsboost commented 5 years ago

Thanks Johannes, I was unaware this is an issue with the mini itself..

From: Johannes Pohl notifications@github.com Sent: Monday, July 1, 2019 3:06:51 AM To: jopohl/urh Cc: vsboost; Mention Subject: Re: [jopohl/urh] PlutoSDR - when transmittion is started the first thing transmitted is some junk (#659)

@vsboosthttps://github.com/vsboost just saw that this is an open issue with LimeSDR-mini: myriadrf/LimeSuite#235https://github.com/myriadrf/LimeSuite/issues/235

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