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Old 13-03-2013, 01:40   #1
AF4MP
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RTL-SDR DVB dongle for DRM

I just posted my first (not very good) attempt at decoding DRM on the 9630 kHz REE Cariari Thread (post #1296) with the RTL-SDR dongle + hf converter.

That signal was not really the best to test the dongle and I'll try tomorrow with the excellent TDP signal from Montsinery.

Has anybody else tried this $10 dongle for DRM decoding?
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Old 13-03-2013, 17:22   #2
F1BJB
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Hi
I am very curious of the results.
I miss the HF converter for trying myself.
I think that the 8 bits dynamic range and the wide bandwidth are the main
problem.
May be using the dongle behind the crystal filter of a up conversion receiver
would be interesting.
Thus the 8 bits would be entirely devoted to the useful signal.
But the cost advantage is lost.
What kind of dongle are you using ?
I have 2 : one with ET4000 and one with R820T front end.
Also interested in the up converter you are using.
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Last edited by F1BJB : 13-03-2013 at 17:39.
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Old 13-03-2013, 21:31   #3
AF4MP
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Hi,

I am using The RTL2832 + R820T DVB Dongle and the hf converter is made by Jani Electronics (all purchased on ebay).

The dongle plus hf converter works very well on the short wave bands!

The connection between the Dongle, DReaM and the sound card is via the Virtual Audio Cable.

I am having problems trying to decode DRM and the result is a lot of re-syncs.

Perhaps this older 2.40 GHz Pentium 4 is too slow for all the simultaneous computation?
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Old 13-03-2013, 22:56   #4
PP5AZF-Ataliba
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I tested the reception with RTL-2832U E4000 + Upconverter. Below are some images of reception GG52QK (São José City (SC) - Brazil:

https://dl.dropbox.com/u/25871636/RT...5-20120218.jpg
https://dl.dropbox.com/u/25871636/RT...0-20130219.jpg
https://dl.dropbox.com/u/25871636/RT...m-20130223.jpg
https://dl.dropbox.com/u/25871636/RT...M-20130218.jpg
https://dl.dropbox.com/u/25871636/RT...20130218-2.jpg
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Old 14-03-2013, 00:17   #5
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Hi Ataliba,

What type of computer were you using?
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Old 14-03-2013, 12:01   #6
AF4MP
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The DReaM analog demodulation works well with the dongle as shown by the 12095 kHz BBC reception.

The interface between dongle/converter and computer, therefore, is working correctly.

Yet with DRM the system has trouble decoding.

When using my normal (external) receiver attached to my (old) computer DReaM re-synchs occur whenever an action such as opening a file, etc., is performed.

So I suppose it should not be surprising that constant re-synchs happen with the dongle as there is more computer processing events happening at the same time.

This will motivate me to build the faster computer (that all the parts have been laying around waiting to be put together)!
Attached Images
File Type: png BBC 12095 kHz RTL-SDR 13March13.PNG (51.1 KB, 946 views)
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Old 14-03-2013, 13:14   #7
PP5AZF-Ataliba
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Quote:
Originally Posted by AF4MP
Hi Ataliba,

What type of computer were you using?

My computer is NOTEBOOK:

MSI, Intel Core i5 CPU M480 @ 2.670 Ghz 4GB RAM, 32 bits, Win 7 Home Premium.

Sometimes need to use 2 sound cards for use in audio decoding with DRM30 DREAM (line out of a sound card connected to the line in of the sound card)

(As vezes preciso utilizar 2 placas de som para utilizar o audio na decodificação do DRM30 com DREAM (line out de uma placa de som ligada ao line in da outra placa de som) )
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Old 19-03-2013, 21:14   #8
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I assembled my new computer over the weekend. It uses a 64 bit AMD Phenom II X4 840 multicore processor operating at 3.20 GHz and 4 GB of RAM.

Using the computers ASUS motherboard sound card and The Virtual Audio Cable I was able to decode TDP on 17875 kHz from Montsinery this afternoon!

Picture of this (but poor quality file) shown on post #282 of that thread.
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Last edited by AF4MP : 19-03-2013 at 21:18. Reason: editorial
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Old 10-04-2013, 02:10   #9
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Hi,
I test this setup this night.
Instead a GUI sdr software, I used the rtl_fm, a command line sdr receiver for rtlsdr.
The advantage of rtl_fm is a low cpu usage.
Computer is a AMD A4-3400 2.7GHz 4GB.
OS is a Linux Debian 6.0.6
Total cpu usage below 20%, most by DReaM.
command of rtl_fm and aplay to send data to aloop device.
rtl_fm -s 48000 -r 48000 -f 61803000 -l 0 -R - | aplay -r 48k -f
S16_LE -t raw -c 2 -D hw:5,0

O windows, yes, have rtl_fm to, aplay can replaced by play (sox), and aloop by VAC or second sound card (or mixing feature do some sound card).

Some images
http://img841.imageshack.us/img841/9...050055pksa.png
http://img827.imageshack.us/img827/2...0409213201.png
http://imageshack.us/a/img856/3117/hubrtlupc.jpg

Bye.
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Old 10-04-2013, 05:57   #10
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pksato can add more information tomorrow if he likes, but I'll comment briefly since I'm already here after posting a log.

Basically, most modern distributions of ALSA already have the driver, snd-aloop, pre-built. Type, lsmod | grep aloop, to check if the module is loaded. If the module is not loaded, as root type, modprobe snd-aloop. Once the module is loaded, if desired one can type, aplay -l, to find the specific device. In pksato's example, the device for the aloop driver on his machine is hw:5.

Briefly, the code uses the ALSA command, aplay, to output a 48 kHz, 16-bit raw stereo signal from the USB DVB receiver to the aloop device which is then used as the input to DReaM. Furthermore, DReaM is configured by default to combine L+R or option -c 2.

Good luck.

Last edited by tpreitzel : 10-04-2013 at 06:03.
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Old 05-06-2013, 19:22   #11
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Quote:
Originally Posted by AF4MP
Has anybody else tried this $10 dongle for DRM decoding?

I ordered one from eBay today and I'll be back when / if I get any results.


Info: The parcel arrived from Hong-Kong yesterday.

More info: In "Funk-Amateur" 7/13 on page 742 there is an interesting article (in German) about an SDR receiver and converter for 1 MHz to 1.7 GHz based on a USB DVB-T Stick with the RTL2832 decoder.
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Last edited by Digger : 26-06-2013 at 18:04.
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Old 30-06-2013, 05:51   #12
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In my previous reply, I should have noted the signal input channel to DReaM should be set to "I/Q Pos" or "I/Q Pos Split"

Last edited by tpreitzel : 27-08-2013 at 05:44.
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Old 06-07-2013, 14:34   #13
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http://sourceforge.net/apps/mediawik...2832U_Guidance
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Old 06-07-2013, 22:08   #14
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Nice link Thanks
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Old 25-08-2013, 17:12   #15
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There is an update to this. The upconverter is not needed any more to receive the 0 - 30 Mhz spectrum. Using direct sampling in the rx application and an Antenna (5 meter wire?) attached to either Pin 1 or 2 of the RTL2832 will allow direct reception of frequencies in 0- 30 Mhz spectrum.
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