[hpsdr] Wide bandscope

[Helmut Oeller]

Hi Bob,

Terminate your Mercury with a 50 Ohms dummy and you'll see nearly the same
noise level over the entire 1. Nyquist zone and no difference between 48K
and 384 k sampling rate. Marginal deviations are caused by slight changings
of the system noise figure. Please note the that PWSDR varies FFT bin width
together with the sampling rate.

You can watch the same behavior using the KISS console.

73, Helmut, DC6NY
 
-----Ursprüngliche Nachricht-----
Von: Hpsdr <hpsdr-bounces at lists.openhpsdr.org> Im Auftrag von Bob Cowdery
Gesendet: Montag, 23. April 2018 12:38
An: hpsdr at lists.openhpsdr.org list <hpsdr at lists.openhpsdr.org>
Betreff: Re: [hpsdr] Wide bandscope

***** High Performance Software Defined Radio Discussion List *****

Just realised I got bounced from the group again so not sure if this got
through or if any replies got junked.


On 4/23/2018 7:48 AM, Bob Cowdery wrote:
> Hi,
>
> I have some questions regarding the wide bandscope. Yes, I'm still 
> playing with Atlas based protocol 1 system after all these years!
>
> Metis V3, Mercury V3.4, Penelope V1.8
>
> 1. Could someone explain what the wide bandscope should show. The 
> noise floor seems to be constant across the frequency range and does 
> not follow the actual noise floor. Also the display varies with the 
> receiver frequency giving the impression that the data is going 
> through a bandpass filter. With 3 receivers all 3 have an effect.
>
> 2. I'm not sure if I should be taking 4096 or 16384 samples to process 
> as the documents are ambiguous.
>
> 3. I've got the implementation wrong somewhere, never been sure about 
> how to process this stuff. I followed what KISS does but have not 
> ended up with the same display. The code for that part is in C so if 
> anyone would like to help spot the problem I will post it.
>
> Thanks for any help
>
> Bob - G3UKB
>

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