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Luis Encinas

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Oct 29, 2016, 1:07:15 PM10/29/16
to Gqrx SDR
Dear Alexandru,

yours is the best (for me) SDR software available today.
But, as any "best-of", I found some strange things.

About demodulator,
I consider one thing is mode and a quite different thing is BW.
So, I fond uncomfortable the "NARROW/WIDE/...." selection.
I woud set TWO modes for FM: "mono" & "stereo". The BW, selected apart, is user responsability.

About working with Ettus,
I miss the ability to select the external reference.
I presume this would be easy. This is the code I use from niusrp.dll :

niUSRP_SetAttributeString(sessionRXHandle,
          "0",
          niUSRP_Attr_ReferenceFrequencySource,
          niUSRP_Val_Terminal_RefIn);

Anyway,
Thank You very much for your work !

Luis Encinas
EA4BGH


Alexandru Csete

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Oct 29, 2016, 2:08:34 PM10/29/16
to gq...@googlegroups.com
On Sat, Oct 29, 2016 at 7:07 PM, Luis Encinas <ea4...@gmail.com> wrote:
> Dear Alexandru,
>
> yours is the best (for me) SDR software available today.
> But, as any "best-of", I found some strange things.
>
> About demodulator,
> I consider one thing is mode and a quite different thing is BW.
> So, I fond uncomfortable the "NARROW/WIDE/...." selection.
> I woud set TWO modes for FM: "mono" & "stereo". The BW, selected apart, is
> user responsability.

Thanks for the feedback Louis, but I don't think I understand what you
mean here... What exactly is the problem?

Normal/narrow/wide are just some presets that depend on the mode,
because different modes have different bandwidths. For instance, it
wouldn't make sense to use a 200 kHz wide filter for AM voice, which
is usually band limited to 10 kHz.

You can see the presets here:
https://github.com/csete/gqrx/blob/master/src/qtgui/dockrxopt.cpp#L31

I'd be happy to adjust them if somebody makes an argument for
different values. However, the use can set the bandwidth to anything
by dragging the edge of the filter box on the FFT plot.

> About working with Ettus,
> I miss the ability to select the external reference.
> I presume this would be easy. This is the code I use from niusrp.dll :

I will take a look at it, but to be sure that I don't forget please
open a feature request on github:
https://github.com/csete/gqrx/issues

It should be possible to do it the same way that we do with antenna selection.

Alex

Luis Encinas

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Oct 29, 2016, 2:54:34 PM10/29/16
to Gqrx SDR
 For instance, it
wouldn't make sense to use a 200 kHz wide filter for AM voice, which
is usually band limited to 10 kHz.


I think the key word is "limited".
Why limit ? This is an experimental software, a general purpose one.

I mean something like this, independent controls for mode and bw:

 
(this is my software, just a trial; not released)

It's clearly right that is stupid to set a 100 kHz BW if you intend to hear 6 kHz AM voice, but what if your intention is other ?
For example, to measure channel pwr on multicarrier transmitters; to watch for two carriers few kHz apart....

Of course, Its just my opinion, based on the use of GQRX, and I'll continue using it if you don't agree on this :)

About the ext reference, yes, similar to antenna selection. Right!

Thank you very much, Alex
Auto Generated Inline Image 1

Alexandru Csete

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Oct 29, 2016, 3:12:45 PM10/29/16
to gq...@googlegroups.com
On Sat, Oct 29, 2016 at 8:54 PM, Luis Encinas <ea4...@gmail.com> wrote:
>>
>> For instance, it
>> wouldn't make sense to use a 200 kHz wide filter for AM voice, which
>> is usually band limited to 10 kHz.
>>
>
> I think the key word is "limited".
> Why limit ? This is an experimental software, a general purpose one.

Ok, now I see what you mean.
The reason why it is limited is that the AM and SSB modes have their
own receiver chain running at 48 ksps rate. This saves a lot of CPU.

One could change this so that for example the "Raw I/Q" would run at
higher rate.

Alex
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