Re: [Discuss-gnuradio] USRP S-Band RX

[Justin Shetty]

I'm using the SBX daughter board. I also misspoke, when I said no attenuation I was actually using a 10dB attenuator that I forgot about.

On Tue, Jul 17, 2018, 16:23 Marcus D. Leech <address@hidden> wrote:

On 07/17/2018 03:10 PM, Müller, Marcus (CEL) wrote:
> Hm, I'd agree, with 60 dB attenuation, we should at least see reduced
> intermod products. OK, you said you had a spectrum analyzer that shows
> the spectrum without these spurs, so I'm trying to rule out TX
> overload/clipping:
> Can you use the screenshot function of that spectrum analyzer (or make
> a good photograph) with at most 100 kHz resolution bandwidth and a
> smaller step size on your SA?
>
> Thanks!
> Marcus Müller
Also, what daughtercard are you using here on your N210.

Is it possible that while you were cabled direct without any attenuation
that the RX saw full-power from the TX?


>
> On Tue, 2018-07-17 at 14:49 -0400, Justin Shetty wrote:
>> I've tried the same test again with 30db and 60db of attenuation. The
>> average strength is lower but the FFT still has the same profile with
>> the repeated spurs. The RX overloading theory seemed promising, but
>> I'm not sure what to make of the situation now that attenuation had
>> little effect.
>>
>> On Tue, Jul 17, 2018 at 2:43 PM Justin Shetty <address@hidden>
>> wrote:
>>> Looks the same as with my flowgraph (which is just the USRP source
>>> going straight to the constellation and fft sinks). Also for
>>> reference I'm using the SBX daughterboard.
>>>
>>> On Tue, Jul 17, 2018 at 1:13 PM Marcus D. Leech <address@hidden>
>>> wrote:
>>>> On 07/16/2018 05:29 PM, Justin Shetty wrote:
>>>>> Hi all,
>>>>>
>>>>> I am working with an s-band radio and am receiving its OQPSK-
>>>>> modulated signal on an USRP N210. The signal I'm seeing on an
>>>>> FFT and constellation plot before any processing are not as
>>>>> expected though. It is very different from the example shown in
>>>>> the GNU Radio tutorial 7 (random source to a constellation
>>>>> modulator to a channel model). I also looked at the signal on a
>>>>> spectrum analyzer and it did not show the repeated peaks I am
>>>>> seeing on my FFT. Does anyone know where I might be going wrong
>>>>> or what's happening?
>>>>>
>>>>> Justin Shetty
>>>>>
>>>>>
>>>>   What happens if you just use the "uhd_fft" utility to view this,
>>>> rather than your own code?
>>>>
>>>>
>>>> _______________________________________________
>>>> Discuss-gnuradio mailing list
>>>> address@hidden
>>>> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
>> _______________________________________________
>> Discuss-gnuradio mailing list
>> address@hidden
>> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio