Re: [Discuss-gnuradio] This is nice

[Marcus D. Leech]

On 03/22/2012 11:17 AM, Andrew Davis wrote:
> Right, but I think the idea here is for $20 why not?
Right, for $20.00, why not indeed!  I just didn't want people making 
long-term plans based on something that amounts to
  a serendipitous accident.

I really don't think doing a UHD driver is the right approach, for 
reasons of maintenance headaches, and support headaches.

But this *does* raise a bigger issue of perhaps needing an abstraction 
layer for "SDR-like" hardware sinks/sources for flow-graphs
  that could reasonably be entirely agnostic about hardware.  Myself, I 
have a couple of "radio science" applications that try to
  be agnostic by supported both UHD devices and gr-fcd--but that 
required two separate flow-graphs because there's no reasonable
  way to abstract that stuff away, which I think is a shortcoming.


> As far as a driver goes what they have now is a program that starts
> the thing and tunes it, then reads samples, all of this is already
> build into the UHD framework. I'm not sure but I would like to make
> this a UHD compatible USB device. ( Much like the USRP1 )
>
> ~Andrew
>
> On Thu, Mar 22, 2012 at 11:06 AM,<address@hidden>  wrote:
> > I also have a trio on order.  The issues I can see surrounding this approach
> > are:
> >
> >     o Consumer electronics parts lineups are capricious and unreliable--the
> > target device may use the "SDR-capable chip" this month, and next month,
> > they've found that they can shave $0.35 of off the B.O.M. by going with a
> > totally different parts line-up they will, even though it will cost them
> > $50K in engineering costs up front--they sell thousands and thousands a
> > month.  There are already *TWO* versions of this dongle, one using the
> > "good" RTL2832U chip, and the other using an Afatech chip (AF9015 or
> > AF9035). The "magic sauce" that Antti discovered in the RTL2832U chip to do
> > "raw samples" is peculiar to the RTL2832U chip, and doesn't necessarily map
> > on to other DVB-T digital demod chips on the market.
> >
> >
> >
> >    o The 28.8MHz master oscillator is a very cheap 100PPM part, which will
> > produce unpleasant frequency offsets, and phase-noise to match
> >
> >
> >
> >    o Not sure how good the noise figure is, since there's no LNA in front of
> > the E4000 tuner chip.
> >
> >
> >
> >    o Don't know how they implement re-sampling.  If it's not done right, then
> > there'll be nasty aliases in the passband handed to the host
> >
> >
> >
> > None of these are fatal, but be aware that the approach of "re-purposing"
> > consumer electronics is fraught with dangers as described above.
> >
> >
> >
> > -Marcus
> >
> >
> >
> > On Thu, 22 Mar 2012 10:53:13 -0400, Tom Rondeau wrote:
> >
> > Andrew and Sean,
> >
> > Glad to hear you both thinking about doing this! Coordinate as you can
> > and keep us up to date on the progress.
> >
> > Tom
> >
> >
> > On Thu, Mar 22, 2012 at 10:45 AM, Nowlan, Sean
> > <address@hidden>  wrote:
> >
> > Funny enough, a coworker mentioned it to me yesterday morning and then it
> > popped up on discuss-gnuradio. He must have seen it on Reddit as well.
> >
> > I have one on order too, and I was also contemplating a GNUradio driver...
> > let me know if you want to coordinate.
> >
> > Sean
> >
> > -----Original Message-----
> > From: address@hidden
> > [mailto:address@hidden On
> > Behalf Of Andrew Davis
> > Sent: Wednesday, March 21, 2012 9:34 PM
> > To: David Kierzkowski; address@hidden
> > Subject: Re: [Discuss-gnuradio] This is nice
> >
> > Saw it on Reddit a couple days ago, already have one on order. Then I might
> > work on making a GnuRadio driver or something for real-time use.
> >
> > On Wed, Mar 21, 2012 at 3:17 AM, David Kierzkowski<address@hidden>
> > wrote:
> >
> > The osmocom guys are using a 20$ USB catv tuner as a RF source in gnuradio.
> > 3.2MS/s !
> >
> > http://sdr.osmocom.org/trac/wiki/rtl-sdr
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--
Marcus Leech
Principal Investigator
Shirleys Bay Radio Astronomy Consortium
http://www.sbrac.org