Re: [Discuss-gnuradio] static peaks spectrum

[Cinaed Simson]

On 01/19/2017 02:16 PM, Marc Pàmies Massip wrote:
> Hey Paul,
> 
> You are right, if I reduce the gain the peaks are reduced too. Do yo
> have an explanation for it?

There are 3 gain settings on the HackRF One, namely, RF gain, IF gain,
base band gain.

The RF gain (which I presume is the LNA in SDR#) should be set to 0.

Unless you live in a rural area, you run the risk of smoking the LNA.

See

   https://greatscottgadgets.com/sdr

Lesson 5 is an introduction to the HackRF One.

> 
> Playing with SDR# I have seen that setting the LNA noise and the VGA
> noise to 0dB all the peaks are removed. If then I increase the LNA noise
> and maintain VGA noise to 0dB the peaks appear again (as it gets higher
> more peaks appear). And finally by increasing the VGA noise the peaks
> just go higher with the rest of the spectrum. However, if after setting
> both gains to 0dB I start increasing the VGA gain a few peaks appear
> too, but not as many as in the other case. Does it makes sense to you?
> 
> Many thanks for your reply,
> 
> Marc.
>>
>> On 19/01/2017 12:19:49, Garver, Paul W <address@hidden> wrote:
>>
>> If you change the receiver gain, does anything happen to the peaks?
>> Try lowering it. 
>>
>> Paul Garver
>>
>>
>> On Jan 19, 2017, at 4:32 AM, Marc Pàmies Massip <address@hidden
>> <mailto:address@hidden>> wrote:
>>
>>> Oh, really? I was using a HackRF-One and sampling at 10MHz.
>>>
>>> Now I've tried with different sample rates (8MHz, 10MHz, 12.5MHz and
>>> 16MHz) and the peaks are always there. Maybe it's true that they
>>> appear more often for higher sample rates, but I am not able to make
>>> them disappear.
>>>
>>> Marc.
>>>>
>>>> On 19/01/2017 9:38:34, Cinaed Simson <address@hidden
>>>> <mailto:address@hidden>> wrote:
>>>>
>>>> On 01/18/2017 01:31 PM, Marc Pàmies Massip wrote:
>>>> > Hi,
>>>> >
>>>> > Maybe this is a stupid question for experts in SDR, but I haven't
>>>> find a
>>>> > clear explanation yet. I know it is normal to have a DC offset in the
>>>> > center of the spectrum, but I am surprised by the amount of static
>>>> peaks
>>>> > that I see sometimes in specific bands (you can find attached some
>>>> > images to better understand what am I talking about). It is
>>>> obvious that
>>>> > those are not "real" signals, in fact when I re-tune the SDR
>>>> peripheral
>>>> > they don't move according to the frequency displacement. I want to
>>>> > understand if it is due to a software problem (the screenshots were
>>>> > taken from SDR#) or if it has something to do with the hardware
>>>> (maybe
>>>> > those are just harmonics from some kind of square signal, i.e
>>>> clock). I
>>>> > am worried because they are extremely strong and because of this I
>>>> could
>>>> > have trouble detecting weaker signals nearby.
>>>> >
>>>> > Summarising, my questions are:
>>>> >
>>>> > - What causes those peaks?
>>>> > - Is it necessary to remove them for a proper signal detection?
>>>> >
>>>> > Thanks in advance,
>>>> >
>>>> > Marc.
>>>>
>>>> You haven't indicated what hardware you used or the sampling rate.
>>>>
>>>> Try reducing the sampling rate - the sampling rate used may be
>>>> unstable.
>>>>
>>>> >
>>>> >
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>>>> >
>>>>
>>>>
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