I was indeed trying to transmit with an empty slot; switching the channel
to 1 fixed the problem.

Thanks for your help!

On Tue, Oct 14, 2025 at 3:16 PM Brian Padalino <[email protected]> wrote:

> On Tue, Oct 14, 2025 at 3:05 PM Daniel Mayer <[email protected]>
> wrote:
>
>> Hello,
>> I am attempting to transmit with a USRP X310 using the 'tx_waveforms'
>> example (./tx_waveforms --rate 25e6 --freq 900e6 --gain 20), but a
>> SignalHound spectrum analyzer placed next to the transmitting antenna of
>> the USRP is not picking up any signal above the noise floor at that
>> frequency. The spectrum analyzer shows signals transmitted by other
>> devices, so it seems unlikely that the spectrum analyzer is broken.
>>
>> The text output of the example is as follows:
>>
>>> Setting TX Rate: 25.000000 Msps...
>>> Actual TX Rate: 25.000000 Msps...
>>>
>>> Setting TX Gain: 20.000000 dB...
>>>
>>> *Actual TX Gain: 0.000000 dB...*
>>> Setting device timestamp to 0...
>>>
>>> *[WARNING] [0/Radio#0] Attempting to set tick rate to 0. Skipping.*Setting
>>> TX Freq: 900.000000 MHz...
>>> Setting TX LO Offset: 0.000000 MHz...
>>> *Actual TX Freq: 0.000000 MHz...*
>>
>> I did notice that the 'Actual TX Gain' and 'Actual TX Freq' are both set
>> to 0; could this be a cause of the problem?
>>
>> For completeness, here are the configuration parameters that the example
>> prints out:
>>
>>> [INFO] [X300] Radio 1x clock: 200 MHz
>>> Using Device: Single USRP:
>>>   Device: X-Series Device
>>>   Mboard 0: X310
>>>   RX Channel: 0
>>>     RX DSP: 0
>>>     RX Dboard: A
>>>     RX Subdev: Unknown (0xffff) - 0
>>>   RX Channel: 1
>>>     RX DSP: 1
>>>     RX Dboard: B
>>>     RX Subdev: UBX RX
>>>   TX Channel: 0
>>>     TX DSP: 0
>>>     TX Dboard: A
>>>     TX Subdev: Unknown (0xffff) - 0
>>>   TX Channel: 1
>>>     TX DSP: 1
>>>     TX Dboard: B
>>>     TX Subdev: UBX TX
>>
>>
> It looks like you have a UBX in slot 1 and nothing in slot 0, but you're
> telling the TX waveforms program to transmit on the default channel (0
> presumably?) which would be the empty slot.
>
> Try changing the subdev or the channel specification to see if you can get
> it to talk to the UBX.
>
> Good luck.
>
> Brian
>
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