[USRP-users] N210 WBX annoying spurs while switching

Dan CaJacob dan.cajacob at gmail.com
Thu Oct 23 02:27:03 EDT 2014


I've never used this, but it looks like the Power Squelch block in GR will
do what you want.  Others who know better will correct me if I am wrong.

Very Respectfully,

Dan CaJacob

On Thu, Oct 23, 2014 at 2:06 AM, bob wole via USRP-users <
usrp-users at lists.ettus.com> wrote:

> Okay, I'll make a custom block in gnruadio to achieve ramp up/down for FSK
> waveform to avoid "keyclicks" .
>
> On Thu, Oct 23, 2014 at 10:52 AM, Matt Ettus <matt at ettus.com> wrote:
>
>>
>> No problem.  The RF filter at the output really isn't the proper way to
>> solve this problem, it will just keep the noise within a band.  What you
>> really want is to avoid putting out energy outside of your channel, and
>> that can only be done with ramping.
>>
>> Matt
>>
>> On Wed, Oct 22, 2014 at 10:46 PM, bob wole <bnwole at gmail.com> wrote:
>>
>>> Thanks Matt for your response, that is the exact answer I was looking
>>> for. Actually I am using USRPs for TDMA and I do not want my time slot to
>>> increase very much. I wanted to know the ramping duration because this will
>>> affect the time slot duration. Second option could be that I can add an RF
>>> filter at the output of USRPs.
>>>
>>> On Thu, Oct 23, 2014 at 10:25 AM, Matt Ettus <matt at ettus.com> wrote:
>>>
>>>>
>>>> Yes, but it is even better to ramp up at the beginning and down at the
>>>> end, and then pad a little bit with zeros.   If you ramp up and down
>>>> smoothly for 1us, you'll confine the emissions to about 1 MHz on either
>>>> side.  All bursty communication systems will do this, like Bluetooth, Wifi,
>>>> even morse code, and most newer standards even specify the ramping rate.
>>>>
>>>> Matt
>>>>
>>>>
>>>> On Wed, Oct 22, 2014 at 10:08 PM, bob wole <bnwole at gmail.com> wrote:
>>>>
>>>>> So you are suggesting that I should zero pad samples at start and end
>>>>> of my burst to avoid this ?
>>>>>
>>>>> On Wed, Oct 22, 2014 at 9:16 PM, Matt Ettus <matt at ettus.com> wrote:
>>>>>
>>>>>>
>>>>>> When you start and stop transmission without smoothly ramping the
>>>>>> signal to zero at the beginning and end, you will create wideband spurs.
>>>>>> Just think about it as amplitude modulation.  Even if you are transmitting
>>>>>> a pure sine wave, if you turn it on and off quickly, it will create out of
>>>>>> band spurs.  Hams call this keyclicks.
>>>>>>
>>>>>> Matt
>>>>>>
>>>>>>
>>>>>> On Wed, Oct 22, 2014 at 1:25 AM, bob wole via USRP-users <
>>>>>> usrp-users at lists.ettus.com> wrote:
>>>>>>
>>>>>>> I noticed that there are a lot of significant spurs generated in the
>>>>>>> output of WBX, on different frequencies randomly, when I use tx_time,
>>>>>>> tx_sob_tx_eob tags. I do not see these spurs if I transmit continuously.
>>>>>>> These spurs appears only when I start and stop transmission using stream
>>>>>>> tags.
>>>>>>> How can I get rid of these spurs and what is the cause?
>>>>>>>
>>>>>>> -
>>>>>>> Bob
>>>>>>>
>>>>>>> _______________________________________________
>>>>>>> USRP-users mailing list
>>>>>>> USRP-users at lists.ettus.com
>>>>>>> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
>>>>>>>
>>>>>>>
>>>>>>
>>>>>
>>>>
>>>
>>
>
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