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

[Martijn Moeling]

In reply to Kevin:

Your path seems pretty similar to mine, I started a few years ago with a RTL 
dongle and got away with receiving in a few SDR programs available for Mac. 
After getting bored by that I installed gnu radio and seemingly quickly I got 
success with getting set-up what I needed. Since everybody can receive but we 
hams can transmit to I fell in love with the b200mini and bought one. So 
created some transmitters (like wbfm stereo with RDS) and as long as it was 
"broadcasting" this worked very well. With a 80W amp I was heard and RDS was 
decoded remotely.

My next step was to make a simplex nbfm trx so I could use my setup for 
communicating over a repeater. I never got this to work as I do not seem to be 
able to get the RX/TX switching to work within Grc. I searched and got answers 
from this list quickly, Tagged stream. Although I understand the concept, I 
never got this working and I have the feeling I miss something. I have a hard 
time formulating the question. 

The mentioning of the RRC filter is something different and sure I need to get 
more theoretical background but my math skills are far away from what is 
needed, currently I combine my extremely demanding job with math learning. 

As a ham operator, I am interested in a multi mode/band SDR solution which I 
can expand with digital modes one by one, up to the point where I can transmit 
analog ATV from say a connected frame grabber and I opted for this as my 
learning curve. Doing so by looking at examples, related theory etc.

If I only could get my b200mini to switch between RX and TX for simplex 
operations I would be a happy man for now.. (Off topic for this thread). But 
all examples I found claiming to do so never worked with my setup. (Most seem 
to switch to null sinks to stop transmitting)

General:
I completely agree with all of the two cents everyone has send. Although not 
everybody is getting that deep into it to make use of gnu radio, as said I want 
my usrp to replace my dedicated rigs.

Martijn



Verstuurd vanaf mijn iPad

> Op 18 mrt. 2016 om 04:10 heeft Kevin McQuiggin <address@hidden> het volgende 
> geschreven:
> 
> 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!
> 
> 73,
> 
> Kevin
> (VE7ZD)
> 
> 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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