Status Update

Mathias Coinchon coinchon at yahoo.com
Wed Mar 21 00:11:06 UTC 2012


Hi Christian,

Despite the great interest in the rtl2832u based stick because of its unbeatable low cost, I'm still looking forward for Osmocom SDR:
- As you said the sensitivity of such low cost USB devices is not so good. The LNA will make the difference and this is important. 

- Quantisation (and filtering if you have added external filters) can make the difference too, especially when sampling on crowded bands with strong adjacent interferers.

- The characteristics these USB sticks are not well known but you are doing measurement and calibration on all bands. This is useful for measurement applications
- Osmocom-SDR design is open and let's hope, here to stay. Who knows, maybe one day realtek may give up baseband sample transfer and do everything on the chip or change the design and so we will be done. I experienced this already with other reverse engineered devices.

- In the future, what will really make the difference is if you add a TX board, none of these OEM USB stick will do it anytime soon and here there's also a great interest from amateur radio to local applications but also for testing, experimentation and why not broadcasting.


So, I am very interested and look forward to Oscomcom-SDR. If it is possible, I would  like to get in the queue to get one from the first batch of 100 .

I am working on the organisation of a new media theme for the next Libre Software Meeting (RMLL) that will happen in Geneva from 7th-12th July 2012: http://2012.rmll.info/ 

Do you think you could present the design ? (or in an another theme if you prefer)

There's a plan to setup a full open hardware and software DAB+ transmission over Geneva for this period using CRC mmbtools. A first successful high power test was done last February in Geneva to test the concept, see: 

http://www.opendigitalradio.org/index.php/Live_DAB%2B_test_transmission_in_Geneva_during_the_EBU_Radio_Week_2012_with_100W_ERP  


The chain could be completed by an open receiver design, showing a real fully free/open chain. The interesting thing is that the Canadian have also implemented CELT free/open audio coding over DAB (as an alternative to the proprietary HE-AAC codec used for DAB+). Standard receivers don't get it but with the SDR approach, this gets feasible.


Cheers


Mathias Coinchon
opendigitalradio.org



________________________________
 De : Christian Daniel -- maintech GmbH <cd at maintech.de>
À : osmocom-sdr at lists.osmocom.org 
Envoyé le : Mardi 20 mars 2012 17h42
Objet : Status Update
 
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Hi everybody,

after a few weeks of apparent silence I'm here to report the current
status of the OsmoSDR stick. I know that a bit more reporting and
general traffic on the list would be good for the project, but please
be patient with us since this project runs in all our spare time - and
there is not much of that...

I have to admit that the advent of the rtl-sdr is bit a kick into the
stomach, but I fear that the problem lies with us and our slow progress.

However I can only stress that the OsmoSDR will be more flexible,
powerful, programmable (even stand-alone operation is possible!) and
sensitive. Many of you don't care much about sensitivity, but you will
notice the difference when you see it...

But now to the facts:
- - the OsmoSDR revision 2 review is completed and the PCBs are ordered
- - depending on the workload of the PCB shop, we have to wait ten to 15
working days for the PCBs to ship to Stefan Reimann (DG8FAC)
- - he will assemble 20 boards immediately (machine time is booked)
- - after that we will tests and checks that no fatal bug remains
- - after that the rest are assembled
- - we will have about 100 boards then (most probably a few will need
some rework as soldering is not a 100% process)

For the revision 2 we changed the following things:

- - clock output of the Si570 was reworked the mitigate voltage level
problems on the E4000 input
- - a lowpass in to E4000 input was added to kill harmonics from the
Si570 (the Si570 produces a square wave signal)
- - a ~20dB LNA was added to increase sensitivity to -125dB @ 450 MHz
(at least we hope so :)
- - a lowpass at the antenna input was added to avoid driving 100mW into
the E4000 when a WLAN near to the stick goes on TX
- - serial wire debugging for the SAM3U was added
- - a few lines at the FPGA were rerouted
- - LEDs moved to the border of the board
- - the board was shrunk 1mm to fit into a casing
- - the expansion pins were moved to fit into the 2.54mm grid (a
breadboard should fit neatly on top)


During the sensitivity tests I did two weeks ago I saw that the RX
spectrum is pretty clean and the RX filters in the E4000 are really good.


So - even with a few weeks delay - we can finally look forward to get
our hands at the OsmoSDR and we will have a really good receiver at
our hands!


Cherio!
Christian

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