Dial_tone.py add_ff()

GNU Radio
1

Another GNU Radio noob here. I’ve been playing around with some of the
examples while I eagerly await my USRP1 and I had a question about the
dial_tone.py example.

I ran the dial_tone.py example that’s part of the 3.3.0 release and
noticed it doesn’t really sound like a (US) dial tone. I’m not sure if I
understand the code correctly but it doesn’t seem like the signals
actually get added together. For example, changing src0 to 440 and src1
to 350 produces a different sound.

I did some more searching on the Internet and found some other examples
using gr.add_ff(), so I added this to the dial_tone.py and it seemed to
do the trick. Did I miss something in the original example? I thought
maybe my libraries were out of date or perhaps I missed something on the
install. I double checked the repository at gnuradio.org and my copy is
the same. I’m running Ubuntu 10.10 on lenovo laptop with gnuradio 3.3.0.

Original source:
— dial_tone.py —
48 dst = audio.sink (sample_rate, options.audio_output)
49 self.connect (src0, (dst, 0))
50 self.connect (src1, (dst, 1))

Changes:

adder = gr.add_ff()
sink = audio.sink (sample_rate, options.audio_output)
self.connect (src0, (adder, 0))
self.connect (src1, (adder, 1))
self.connect(adder, sink)

Cheers,
-Tim

2

The intention of the original example was to play the two tones on
separate speakers (left and right). Might not work on
all sound systems/configurations.

–
Marcus L.
Principal Investigator
Shirleys Bay Radio Astronomy Consortium

3

The intention of the original example was to play the two tones on
separate speakers (left and right). Might not work on
all sound systems/configurations.

Thanks for clarifying this, apparently my speakers weren’t balanced (had
left only) hence the different sounds when swapping sources. I had also
incorrectly assumed that dial_tone.py was set up the same as the GRC
example which uses an adder. Once I fixed my speakers though everything
worked out, I probably spent over two hours just adding different
saw-tooth, square and triangle waves together and messing with the
frequency sliders.

Cheers,
-Tim