RSP1 and ExtIo 4.1 and Decimation

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CaptainNemo
Posts: 134
Joined: Mon Jan 05, 2015 1:22 pm
Location: Genoa - Italy

RSP1 and ExtIo 4.1 and Decimation

Postby CaptainNemo » Fri Nov 17, 2017 11:47 am

Hi all.
Last evening I downloaded ExtIo 4.1 that I use with RSP1 and sdr#.
Fine to see there is a new parameter "decimation". Well done sdrplay team!
Even if we all are not radio engineers, most people in this forum have a general technical-scientific imprinting... so forgive me if I cut those concept with an axe...
Use case: HF SWLing. Displaying 200kHz on the screen is good enough for this use.
So I set 200kHz IFbw I get SR 2M decimation 8 and "final SR" 0.25 (Piece of cake... Shannon, Nyquist, prof. R. Lyons all in a good mood, all happy and satisfied).
I know sdrplay rsp1 can display 8M at a time, so I'm legitimate to think it can sample at 8M (at least, taking into account quadrature...).
Q1. The question is: why the extio don't allow to see a 200k span sampling it at 8M and decimate lets say 16 times? (8M/16 means 500k letting also some "fat" around the desired bw of 200k). Why not?
Q2. maybe there is some doc here on the website explaining this but i have some trouble in finding it, can some one head me to the place?
Q3. can we say decimating 16 times means 2 more bit in resolution in sdrplay? (here I'm asking in particular for sdrplay implementation...)
Thanks in advance.
gio

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CaptainNemo
Posts: 134
Joined: Mon Jan 05, 2015 1:22 pm
Location: Genoa - Italy

Re: RSP1 and ExtIo 4.1 and Decimation

Postby CaptainNemo » Sat Nov 18, 2017 5:40 pm

edit:
for some strange reason I succeed for a while to "unlock" the decimation drop down list...
so I got
zero if
if bw 200 khz
SR 8.00 M
decimation 16
unfortunately it was only for a moment...
I did click somewhere else and now it is again locked...
anyone has the same issue?
gio

Reason: No reason

Tech_Support
Posts: 243
Joined: Mon Jun 01, 2015 7:00 pm

Re: RSP1 and ExtIo 4.1 and Decimation

Postby Tech_Support » Mon Nov 20, 2017 12:54 pm

Hello Gio,
It is necessary to ensure that your IF bandwidth is less than the final sample rate to reduce the risk of spurious response as a result of aliasing. You should be able to enable a decimation factor of 16 with an 8 MHz sample rate if you have first set the IF bandwidth to 300 kHz or less. If you leave the IF bandwidth at 8 MHz, decimation will not be possible.

As a general rule, we would recommend using the lowest native sample rate first and then pick the decimation factor. This will give the lowest CPU load. For example, if you want to view 200 kHz bandwidth, the best settings would be:

IF BW = 200 kHz, SR = 2 MHz, Dec=8

This is better than:

IF BW = 200 kHz, SR = 8 MHz, Dec=32 as this will use a higher CPU load for no benefit.

Sincerely

SDRplay Tech_Support

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CaptainNemo
Posts: 134
Joined: Mon Jan 05, 2015 1:22 pm
Location: Genoa - Italy

Re: RSP1 and ExtIo 4.1 and Decimation

Postby CaptainNemo » Mon Nov 20, 2017 6:22 pm

Hi Tech Support, thank you for your answer.
Tech_Support wrote:...You should be able to enable a decimation factor of 16 with an 8 MHz sample rate if you have first set the IF bandwidth to 300 kHz or less...

I'm sorry not to be clear. Sorry for my bad english. Anyway what i wanted to do is exactly what you say:
IF 200k (less than 300k), sample rate 8 Mhz and I would like to set decimation 16... just to try... I'm not afraid of images since they are our daily bread with those low-cost sdr... but i could not set 16 nor 8... I suppose there is a bug.
To be honest, only one time cycling like a mad among those drop down list suddenly decimation ddl unlocks but I cant reproduce what I did
and currently I set IF bw 200khz and SR 8 then I see decimation NONE and I cant change this value.
Please help me to unlock this situation.
As I wrote I use 4.1 extIO with sdr# 1361, nevertheless according to me what happen inside the extio panel is widely independent from the "host"...
Thank you.
Gio

Reason: No reason

Tech_Support
Posts: 243
Joined: Mon Jun 01, 2015 7:00 pm

Re: RSP1 and ExtIo 4.1 and Decimation

Postby Tech_Support » Mon Nov 20, 2017 7:28 pm

Hello Gio,
I will check again for what you were seeing, but so far, I have not been able to replicate your problem. If I can repeat it, it will certainly be a bug, which we will fix. Just to confirm, you are setting a sample rate of 8 MHz, IF BW of 200 kHz, and you do not have the option for any level of decimation other than "none", correct?

Sincerely

SDRplay Tech_Support

Reason: No reason

CaptainNemo
Posts: 134
Joined: Mon Jan 05, 2015 1:22 pm
Location: Genoa - Italy

Re: RSP1 and ExtIo 4.1 and Decimation

Postby CaptainNemo » Mon Nov 20, 2017 7:52 pm

sdrplay extio version 4.1 build 1115

if mode=zero if
if bandwidth=200kHz
sample rate(mhz)=2.00
decimation=8 (no other values in the drop down list)
final sr= 0.25MHz

if mode=zero if
if bandwidth=200kHz
sample rate(mhz)=8.00
decimation=None (no other values in the drop down list)
final sr= 8.00MHz

if mode=zero if
if bandwidth=600kHz
sample rate(mhz)=6.00
decimation=None (no other values in the drop down list)
final sr= 6.00MHz

windows 7 professional, service pack 1

bye
gio

Reason: No reason

sdrplay
Posts: 626
Joined: Wed Jan 07, 2015 7:58 am

Re: RSP1 and ExtIo 4.1 and Decimation

Postby sdrplay » Mon Nov 20, 2017 8:34 pm

I also can't reproduce that here. I just want to make sure this isn't a rendering issue. When you've got decimation highlighted, can you see if other menu options are available by using the up and down arrows?

Before you start your test, can you click "Load Defaults" to make sure we're both starting at the same position. When I follow your steps I see other decimation options always available.

Best regards,

SDrplay Support

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CaptainNemo
Posts: 134
Joined: Mon Jan 05, 2015 1:22 pm
Location: Genoa - Italy

Re: RSP1 and ExtIo 4.1 and Decimation

Postby CaptainNemo » Tue Nov 21, 2017 8:33 am

My test case follows this sequence:
1. set the if mode to zero IF
2. set the if bw 200khz from the drop down list
3. set the SR 8.00 from the drop down list
4. set the decimation from the drop down list (if any available...)
5. read the "info" about the final SR reached
Right?
Any way I will try again this evening... so if there are other "instructions" let me know...
bye
gio

Reason: No reason

Tech_Support
Posts: 243
Joined: Mon Jun 01, 2015 7:00 pm

Re: RSP1 and ExtIo 4.1 and Decimation

Postby Tech_Support » Tue Nov 21, 2017 6:10 pm

Hello Gio,
We can confirm that this is a graphics rendering issue that only seems to show up with SDR#. We do not understand what is causing this, but have seen it with other ExtIO plugins. This problem does not occur with HDSDR, which was why we struggled to replicate your problem.

The options are there, but you don't see the drop-down menu. To select a different decimation factor, simple click on the decimation button and use the down arrow or up arrow on your keyboard to move between different decimation factors.

Sincerely

SDRplay Tech_Support

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CaptainNemo
Posts: 134
Joined: Mon Jan 05, 2015 1:22 pm
Location: Genoa - Italy

Re: RSP1 and ExtIo 4.1 and Decimation

Postby CaptainNemo » Tue Nov 21, 2017 7:51 pm

Using arrows now I can change those values...
Thank you very much for the trick.
Now I can start testing what setting is best for me.
gio

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