Still a newbee

GNU Radio
1

Hi all,

For the life of me I still can not figure out how to properly build an
AM
and SSB receiver. Using grc I am able to build and run FFT sink and
observe
the AM broadcast band spectrum and control the frequency. But I can not
detect the audio. (I have not yet tried to build an SSB receiver.God
forbid.)
I tried various filters and AM DEMOD. When I install the AM DEMOD I keep
getting an error message “number of taps must be >=3.” Can anyone tell
me
how to build an AM/SSB receiver using grc? I have searched the web but
haven’t found anything.

Searching the gnuradio directory I found hf_explorer, hf_radio and
usrp_am_mw_rcv.py. These files appear to be what I am looking for but I
have
not been able to figure out how to install and run them under python.
Can
anyone instruct me on how to get these files/programs up and running?

I have spent hours and hours trying to figure it all out (and searching
the
web)but so far I haven’t been successful. Is there any way to get an HF
receiver up and running without the need to become an expert in python,
C++,
etc? I do want to learn to use python, C++, etc so that one day I can
write
some blocks but I would like now just to get a receiver up and running
to
play with.

Thanks for your help,

Steve

2

For the usrp_am_mw_rcv.py; if you have an USRP you should just be able
to
run it and it will work, ie (may need to be in the right directory?):

python usrp_am_mw_rcv.py

As for making in GRC I am afraid I cannot help much since I never use
it. It
shouldn’t be to hard to pick up the level of python needed to create a
flowgraph however. usrp_am_mw_rcv.py seems to be pretty much what you
want;
look at how the flow graph is connected in there to get an idea of what
blocks you will need in GRC.

This is the line which describes all the blocks in the flow graph:

self.connect (self.u, self.chan_filt, self.am_demod, self.audio_filt,
self.volume_control, audio_sink)

You should only need self.u (ursp source), chan_filt (anti aliasing and
down
sampling), and am_demod to get an audio signal which you can hear.
Important
to remember to downsample to the correct freq! Ursp ADCs run at 64 MS/s
so
with max hardware decim (250) the samples come in at 256KHz, meaning you
AA
/ downsampling filter needs to decimate a further 8 to get to 32KHz
(probably what your sound card runs at). In usrp_am_mw_rcv.py they use 4
decim in chan_filt then 2 in audio_filt so will need to take that into
consideration and not just use their filter coefficients ;-).

Hope that helps,
Kieran