How to configure filter width

[Kevin Palivec]

I just started getting into SDR and I've been using gqrx.
I've looked and looked but I cant seem to find out how to edit the filter width.
so now the dumb noob question!

Is there a way to build your own filter width presets and if so. how?

Thanks for any help!
Kevin

[Jasper Ragworth]

I've found the width changes if you click and drag somewhere in the filter frequency. I do this occasionally and it's never intentional :-)

[Alexandru Csete]

On Thu, Jul 12, 2012 at 6:30 PM, Kevin Palivec <raht...@gmail.com> wrote:
> I just started getting into SDR and I've been using gqrx.
> I've looked and looked but I cant seem to find out how to edit the filter
> width.
> so now the dumb noob question!
>
> Is there a way to build your own filter width presets and if so. how?

Normally, you would see the filter width as a shaded area on the FFT
plot: http://flic.kr/p/aJdRmB
This is with the narrow band Funcube Dongle and here people find out
that they can drag the edges to the left and right using the left and
right mouse buttons.

The problem is that the rtl-sdr has a very wide bandwidth compared to
a standard AM/FM/SSB filter so the filter area (including the mouse
grab area) becomes practically invisible. Apparently, as Jasper
witnessed, it is still possible to grab the filter edges :-)
To improve this I added the wide/normal/narrow shortcuts which are
mode dependent. I have also been working on an additional control to
tune the filter width and offset, however, due to the necessity of
making rtl-sdr support available I didn't have time to finish it. So
it is on the todo list but not yet available.

Ideas and input on this matter are welcome. I have been thinking about
adding two widgets that can work in two modes:
(1) filter width + offset
(2) lower + upper cutoffs
I suppose people would be interested in storing and recalling filter settings.

Alex

[Jasper Ragworth]

I know it's less easily "discoverable", but how about <modifier>+mouse scroll, eg ctrl+scroll to scale the width of the filter? That way it doesn't depend on precision mousework with the wider-bandwidth SDR sources, and is less likely to be triggered unintentionally.

Also, a fourth filter option in each mode, "custom", or the ability to edit the existing ones, would probably satisfy most use cases.

[Alexandru Csete]

All right, this was relatively easy to add and is now available in git/master.

CTRL+wheel will adjust the filter width
SHIFT+wheel will adjust the filter shift (useful for SSB/CW)

The filter selector will switch to 'User' and also display the current
width. Selecting 'User' directly in the combo does not work yet.

Alex

[Jasper Ragworth]

Top work, as ever. You couldn't buy customer service like this!