[Hackrf-dev] feedback on lesson 1

[dan farmer]

FWIW, coming from a neophyte in the space, I thought it simply tremendous;
the only thing I might quibble about was the lack of links pointing to
it, as I found it, lost it, and then took forever to re-find it (I put
a link up on the wiki to save me in the future ;))

Looking forward to more - are you going to do a set number, or make it
like a college course of 15 weeks or so of classes, or…?  And any plans
on the frequency also?  While I’m asking, an RSS on the main page would
be nice… yeah, yeah, your reward for giving is more asking, you know
how it goes…

Also selfishly hoping you’ll be covering more out-of-gnuradio-companion 
python trix o’ the masters, as that’s my own personal interest ;)

dan


On Aug 22, 2014, at 6:53 AM, Michael Ossmann <mike at ossmann.com> wrote:

> On Fri, Aug 22, 2014 at 06:08:01AM +0200, Joris wrote:
>> 
>> Hopefully it's ok to post some feedback on the SDR lesson 1.  All in
>> all I was very pleased. The format and teacher make it extremely
>> accessible.
> 
> Thanks for the feedback, Joris.  I think this is a fine place for this
> conversation.
> 
>> * If there are any good questions below or in the mailing list,
>> perhaps they can be converted into a "FAQ" on the lesson page?
> 
> I'm making a private list of questions people are asking me, and I'll be
> sure to address them in future lessons.  I do not intend to answer
> questions in written form (at least until I finish the video series).
> 
>> * It might be worthwhile to refer in the same spot to the ("lesson
>> 0"?) getting started documentation that exists already. I realise that
>> is not strictly the point of the lesson, but it might save some people
>> some frustration.
> 
> Is it not enough to link to that page in both the homework and resources
> section of the lesson 1 page?
> 
>> * Low pass filter: I may have missed it, but you emphasise the effects
>> for the CPU, but it's even more important for the listener (ie, no
>> noise).
> 
> I'll talk a lot more about filtering in future lessons.
> 
>> * Low pass filter bis: why is the transition width 25? In playing
>> around I found that 90/10, 75/25 and even 50/50 seem to work fine?
> 
> I'll talk a lot more about filtering in future lessons.  You could
> probably go as low as 45/5 and have it still work.  If the cutoff is too
> low, the audio will be degraded.  If the transition width is too low,
> your CPU may have trouble keeping up.
> 
>> * Low pass filter vs rational resampler: It seems there is a huge cpu
>> difference between doing the first decimation in the LPF vs doing
>> everything in the rational resampler. (my system can fun the former
>> just fine, the later is utterly unworkable). Is there no way to put
>> the decimation in a separate block?
> 
> Nice observation!  I'll talk a lot more about decimation (with and
> without filtering) in future lessons.
> 
>> * Perhaps it's a good idea to post a still screenshot of endpoint of
>> lesson 1. Posting the GRC file might be a good idea also, although it
>> might end up reducing tinkering.
> 
> There is a screenshot of the flowgraph in the homework section, and the
> .grc file is posted in the resources section.
> 
> Mike
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