[Discuss-gnuradio] Newbie questions

[ChoJin]

Hello,

I'm new into gnuradio, so sorry in advance for the very basic 
questions. I'm trying to read the code whenever possible but it takes 
times to get used to it :)

I'm playing around with the wfm receiver, adding time domain scopes, 
trying to get the stereo out (yes I saw someone has done it before ;) 
), new slide bars etc... just playing around to get familiar with the 
beast in other words.

First, I'm trying to understand why I don't get the whole 100khz band 
when I plug an fft_sink_f to the self.guts.deemph.
I only get from 0 to 16kHz whereas I was expecting to get something 
close to:
http://www.linuxjournal.com/files/linuxjournal.com/linuxjournal/articles/075/7505/7505f7.png

Could someone explain?

Also could someone explain the cutoff values from (and what is the 
passband ripple parameter using an intuitive explanation) from:
        chan_filt_coeffs = optfir.low_pass (1,           # gain
                                            usrp_rate,   # sampling rate
                                            80e3,        # passband 
cutoff
                                            115e3,       # stopband 
cutoff
                                            0.1,         # passband 
ripple
                                            60)          # stopband 
attenuation

why 80k and 115k?

Next, I'm trying to build a double slider for the frequency. One slider 
to set a rough frequency, and another slider to fine tune it more 
precisely. Kind of two synchronized sliders which get both updated (as 
well as the textbox with the exact frequency value) when one is moved. 
Is there any example around I could get inspiration from (I'm not 
familiar with wxWindow yet).

And finally I would like to extend it to be able to choose between 
different modulation mode (AM, CW, WFM...)
I wonder if I should start looking at the mblock for that, given the 
dynamic graph capability (from what I understood by reading the ML, 
with the mblock we can unplug block and replug new one in real time, 
which seems to be suitable in this case). Or maybe there is an easier 
solution?

I think that's pretty much it for my first day of experiment,

Thanks for any pointers you could provide,

-- 
Best Regards,
ChoJin