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Re: [Discuss-gnuradio] dive into gnu-radio

From: Kevin McQuiggin
Subject: Re: [Discuss-gnuradio] dive into gnu-radio
Date: Thu, 17 Mar 2016 20:10:38 -0700

Hi Martijn:

Two cents from me, a relative non-technical newbie, also a long-time amateur 
radio operator.  My educational and professional background is in computing 
science and a bit of math.

I first found gnuradio a few years ago, and had a similar experience to yours.  
I played around with it, did some of the tutorials, but quickly got slain by my 
lack of technical DSP background, and (back then especially) the lack of clear 
documentation on the blocks.

I got discouraged and removed my gnuradio installation.

However, I knew that I wanted to know more, and understand gnuradio better, as 
the power of the package was obvious to me.  I saw this as a learning 
challenge.  I embarked on what ended up being about 1.5 years of reading and 
coding, outside of gnuradio.  

I found a fantastic couple of books, most notably the free "Digital Signal 
Processing: A Guide for Scientists and Engineers".  See http://dspguide.com.  I 
eventually bought a hardcopy of the book.

I used the book to code up some self-learning programs, for example a DTMF 
decoder, and got my head around a lot of the DSP concepts.  More reading 
augmented this, and I returned to gnuradio about a year ago with a $20 RTL 
dongle in hand.

The tutorials now made more sense, and while I was still on a steep learning 
hill, things went well.  I upgraded my hardware to an Ettus B200, and now feel 
a bit on top of things.  Stick with the cheap dongle for awhile.  I initially 
upgraded to the B200 as I wanted to build a transmitter.  However the RX is WAY 
better on the Ettus unit too, it was a fantastic jump and good investment.

If you have time and no particular deadline, I'd recommend this approach.

As for projects, I've built an FM RDS receiver and decoder, an FM SCA receiver, 
an SCA transmitter,  Multi-channel HF CW decoder (via an up converter), and am 
currently working on a clear channel Inmarsat decoder - this one is about half 
done.  My approach is to use gnuradio for the demodulator, then pipe the 
bitstream to a C program over a gnuradio TCP or UDP sink.  The RDS code, for 
example, is almost 1000 lines of C, so these things are not intrinsically 
"easy".  Incredible learning value and sense of satisfaction though when your 
code/flowgraph actually works!

Things like the need for an RRC filter become clear with reading, review of 
(say) RDS specs, and head scratching over a couple of weeks.  Read about 
"matched filters" and you'll understand what the RRC block does.

My recommendation is to recognize that this is a non-trivial field and big 
learning opportunity, and grab a couple of books like the (free) one by Smith 
above.  Read for awhile, then see where you're at.

It does grow on you with research, but I also have to say that my knowledge is 
"stone knives and bear skins" to quote a popular Vulcan, compared to the level 
of knowledge of most of the folks on this list.

Hope these comments help in some way!



Sent from my iPad

> On Mar 16, 2016, at 2:10 PM, Martin Braun <address@hidden> wrote:
>> On 03/16/2016 01:33 PM, Martijn Moeling wrote:
>> I feel there is a gap between the knowledge of the experts and the
>> information for newcomers. My questions have been answered pretty
>> quickly but the answers raise even more questions and confuse me.
> This is a common concern, but it's really, really hard for us as a
> community to address comprehensively. There's multiple reasons for that,
> but it all comes down to the fact that writing good tutorials is hard.
> Many of us core GNU Radio members have a DSP/Wireless background and
> then moved into GNU Radio. For people like us, you need completely
> different tutorials than for someone who's not familiar with DSP.
> Now, there's lots of very good books out there that go into DSP and
> wireless communication. They're usually written to address
> university-level students. But how do we condense them into nice and
> easy tutorials? It's hard.
> It gets exacerbated by the fact that writing tutorials becomes harder
> the more familiar you get with a topic. You lose sight of what's hard,
> and what's not. Unless you're a professional tutorial writer, of course
> -- but we have very few of those.
>>> What I need is: 
>>> 1) understand the blocks, their purpose and what they do
>>> 2) learn how to create a minimal scenario using grc
>>> 3) learn how to create blocks of my own
>>> 4) create more complicated scenario.
>>> I wanted to ask the same question in stackoverflow, as I have seen
>>> people from the community hanging around there. But, the amount of
>>> shitstorm coming from there is amazing when asking about learning
>>> pointers... They mark the Q as "opinion-based" immediately.
> SO can be tough like that. Also, 'gnuradio' tagged questions don't
> usually get a lot of attention. I'd be happy to see more action on SO,
> but we never really got there.
> Back to your list, 3) is comprehensively covered by the guided
> tutorials, as are parts of 2) and 4). 1), however, is where we get into
> the tricky scenario I went into above.
> I'm afraid I don't have easy answers for you here. All I can say is I
> hope people stay encouraged to submit documentation patches and
> tutorials, to make this all more accessible. We certainly don't want
> this to be available to only an elitist bunch of DSP nerds.
> Cheers,
> Martin
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