[Discuss-gnuradio] Re: help on xlating frequency

[Markus Feldmann]

Paul Mathews schrieb:
> See 'usrp_am_mw_rcv.py' for an example. Look for the code relating to these
> lines in particular:
>
>         if self.use_IF:
>           # Turn If to baseband and filter.
>           self.chan_filt = gr.freq_xlating_fir_filter_ccf (chanfilt_decim,
> chan_filt_coeffs, self.IF_freq, usrp_rate)
hI pAUL,

i used this example as possible as i can, but this
frequency translating filter has one important difference
to my application, the FFT-Plot-sink which is connected to this
xlating filter is staticly.
I have a slider to change my baseband to the wished spectrum, so
my xlating filter it is dynamically.

I still doesn't know whether to use a low_pass is usefull
or a band_pass. The low_pass doesn't delete the middle
signal in the FFT-Plot in my tryings.

Further on i doesn't know which conditions have to be made to
let my application work fluidly ?
Which decimation ?
Which rate is useful ? Should it use the same rate, than
the element before ?
Which is the centerpoint from which the low_pass_cutoff
and the high_pass_cutoff frequency will be counted ?
I tried it out, but still doesn't know how it works.

Regards Markus