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AF4MP
13-03-2013, 01:40
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?

F1BJB
13-03-2013, 17:22
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.
73

AF4MP
13-03-2013, 21:31
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?

PP5AZF-Ataliba
13-03-2013, 22:56
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/RTL-Upconverter/DRM-11715-20120218.jpg
https://dl.dropbox.com/u/25871636/RTL-Upconverter/DRM-RUV-2A-11635-SODIRA-0550-20130219.jpg
https://dl.dropbox.com/u/25871636/RTL-Upconverter/HDSDR-RTL-Upconverter-28m-20130223.jpg
https://dl.dropbox.com/u/25871636/RTL-Upconverter/OM-20130218.jpg
https://dl.dropbox.com/u/25871636/RTL-Upconverter/RNZI-17675-20130218-2.jpg

AF4MP
14-03-2013, 00:17
Hi Ataliba,

What type of computer were you using?

AF4MP
14-03-2013, 12:01
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)!

PP5AZF-Ataliba
14-03-2013, 13:14
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) )

AF4MP
19-03-2013, 21:14
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.

pksato
10-04-2013, 02:10
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/img841/9159/1181513041000050055pksa.png
http://img827.imageshack.us/img827/2171/20130409213201.png
http://imageshack.us/a/img856/3117/hubrtlupc.jpg

Bye.

tpreitzel
10-04-2013, 05:57
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.

Digger
05-06-2013, 19:22
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.

tpreitzel
30-06-2013, 05:51
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"

alokesh
06-07-2013, 14:34
http://sourceforge.net/apps/mediawiki/drm/index.php?title=RTL2832U_Guidance

F1BJB
06-07-2013, 22:08
Nice link Thanks

desai_amogh
25-08-2013, 17:12
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.

alokesh
25-08-2013, 17:22
Post details if you have done it .....

Digger
31-08-2013, 10:55
Hi all interested people,

I took my RTL USB dongle apart and located the pins 1 and 2 on the RTL2832U. In my version those two pins are fitted with coupling capacitors, C33 and C34. Connecting an antenna to pin 1 did not produce any results at all. Then I removed C34 and connected my active antenna via a 0.022 uF capacitor in series.

With the SDR# v1.0.0.163 set to Direct sampling (I branch) I can listen to KBC Radio on 6095 kHz with quite good results now around midday in Sweden.

mvs sarma
31-08-2013, 15:40
Hi all interested people,

I took my RTL USB dongle apart and located the pins 1 and 2 on the RTL2832U. In my version those two pins are bypassed to ground with two capacitors, C33 and C34. Connecting an antenna to pin 1 did not produce any results at all. Then I removed C34 and connected my active antenna via a 0.022 uF capacitor in series.

With the SDR# v1.0.0.163 set to Direct sampling (I branch) I can listen to KBC Radio on 6095 kHz with quite good results now around midday in Sweden.
Encouraging experiments Digger,
Many thanks

F1BJB
31-08-2013, 16:11
It might be interesting to feed it from a 455Khz IF thus bypassing the use of 12Khz converter
and sound card.

Digger
01-09-2013, 16:53
I must admit that I am not a computer specialist, and I wonder if someone could hint how to listen to DRM with Dream and SDR Sharp in Direct Sampling Mode? How to get the SDR# signal into Dream without getting the noise out into the speaker. Need two sound cards?

F1BJB
02-09-2013, 18:24
Hi
I'm not an expeet either.
The idea is to use a software that looks as a sound card
In your front software SDR# instead of your sound output you chose the input of the virtual sound card
Then in the DRM decoding software instead of your real sound card as input you choose the output
of the virtual sound card.
I used VB audio as virtual audio card.
http://www.vb-audio.com
There is another one called VAC for virtual audio cable
It worked but as my favorite software SODIRA support DRM and I'm used to it I didnt insist.

mvs sarma
04-09-2013, 09:14
Hi
I'm not an expeet either.
The idea is to use a software that looks as a sound card
In your front software SDR# instead of your sound output you chose the input of the virtual sound card
Then in the DRM decoding software instead of your real sound card as input you choose the output
of the virtual sound card.
I used VB audio as virtual audio card.
http://www.vb-audio.com
There is another one called VAC for virtual audio cable
It worked but as my favorite software SODIRA support DRM and I'm used to it I didnt insist.
i fear that VAC might have some delay related issues handling dream decoding.
Instead
the analog stage the iq signals from USB can be directed to VAC
and later f the dream can work from real sound card, getting the input from VAC and real sound card can decode and give audio at its line out as idf headphone or speakers.

F1BJB
04-09-2013, 16:00
Hi
I think that what comes out of an RTL2832 dongle doesn't look like the output of an USB sound card
It is only 8bits with a very high sample rate reaching 3Mbps.
So no audio software can deal with it as it can with a Funcube dongle.
Only SDR software that are specially written can deal ,with the output of RTL2832
Instead of using a virtual audio sound card at the output I think we could try to decode DRM as
USB with a 10 Khz bandwidth centred on the signal and the carrier a few Khz lower.
Then record the noisy audio as a *.WAV file.
Later feeding that file to DREAM could do the trick.

F1BJB
04-09-2013, 16:16
Connecting an antenna to pin 1 did not produce any results at all. Then I removed C34 and connected my active antenna via a 0.022 uF capacitor in series.

Hi
I would recommend not to try connecting a real antenna directly to any pin of an IC.
It is a good way to destroy an IC by ESD
Instead use some kind of high pass filter and may be clamp diodes to ground.
At least reduce the value of the capacitor as much as you can.

Digger
04-09-2013, 17:57
Hi
I would recommend not to try connecting a real antenna directly to any pin of an IC.

I'm aware of that after having spent my entire life as an RF design engineer, but on the other hand 10 USD is not a fortune. ;)

And, your ideas in your post #23 are worth looking into....

F1BJB
04-09-2013, 19:57
Sorry .I could have guessed that having had a look at your website.
Let us say it's a warning for the less experienced.
I too spent my active life in that field.

Digger
27-09-2013, 16:12
Slowly, slowly I am getting my antenna rigged up, soon I'll report on the dongle plus Dream via the virtual audio cable. I have a feeling that I would have to add some RF gain and a tuned circuit between the antenna and the dongle.

mvs sarma
03-10-2013, 15:22
Slowly, slowly I am getting my antenna rigged up, soon I'll report on the dongle plus Dream via the virtual audio cable. I have a feeling that I would have to add some RF gain and a tuned circuit between the antenna and the dongle.
the dongle has an inbuilt level(gain) adjustment, i suppose. please check before any such trial

F1BJB
04-10-2013, 07:37
Hi
I'm not sure that RF gain is available if you bypass the tuner.

Digger
12-10-2013, 09:00
Just a short report of not much progress with my RTL Dongle, SDR#, Virtual Audio Cable and Dream. In Direct Sampling Mode and USB with >12 kHz filter bandwidth I can get a Label in Dream, but so far I have not been able to get any decoded audio. :o

Siber
27-10-2013, 00:24
but so far I have not been able to get any decoded audio

Hi, Digger.
The VAC bitrate should be not below 48 bps, check it out.

Digger
14-04-2014, 16:21
In the meantime the RTL2832U works quite well on DRM in direct sampling mode together with VB-CABLE. Some kind of pre-selection or bandpass filters in the antenna circuit is necessary if you want to get rid of birdies caused by local FM transmitters. I'll post some logs later.

Aetheradio
20-12-2014, 00:49
In the meantime the RTL2832U works quite well on DRM in direct sampling mode together with VB-CABLE. Some kind of pre-selection or bandpass filters in the antenna circuit is necessary if you want to get rid of birdies caused by local FM transmitters. I'll post some logs later.


I've been doing a bit of catch-up having recently got the RTL2832u with the 820t tuner.

For use below 24 MHz I select direct sampling Q input
I found the easiest way to safely do this was to run a small ferrite bead choke of about 10 turns from the existing input connector across to a 100pF capacitor which connects to the AD IC pin 4. This method preserves the use of overload protection doides on the board, as well as using the original connector for all input and the case fits in place (removed the IR diode). I did this by heating the capacitor lead and waiting for solder to run to the chip pin viewed under a magnifying glass. there is also a 100 pF capacitor from the choke to ground. The purpose of this is to low pass 30MHz to Q input and reject above 30 MHz. It also mechanically anchors the choke wire. I used the info here
http://www.superkuh.com/rtlsdr.html
My dongle is the small stubby one unfortunately there is a lot of switching power supply noise around 500 kHz and 1 MHz and this model doesnt have an easy way to replace the supply with a linear regulator like some posters have done to eliminate these signals.

To use in the SW bands it helps to select the below 15 MHz segment or the above 14 MHz with some filtering - an antenna tuner will do this. If signals are too strong I add a 10dB attenuator inline.

The performance is not spectacular with the many compromises of the 8 bit dongle and no onboard filtering 'proper' models like FCDpro+, FiFi or AFEDRI would do much better.

To get a DRM decode I used VB Cable on a Sony Vaio laptop Win7.

Although I prefer the look of SDR# it doesnt work well on this laptop with annoying audio pops occuring especially if waterfall and main spectrum display are in use.

So I use HDSDR as the tuner program and select DRM as the mode.
DRM audio works fine the performance is about 4 dB worse MER than my best analog radio setup with 12 kHz soundcard to the same PC.

F1BJB
12-03-2015, 15:45
Another link :
http://www.rtl-sdr.com/new-experimental-r820t-rtl-sdr-driver-tunes-13-mhz-lower/

LoTHar57
31-05-2015, 09:31
hello, when use the drm log plotter a message appears; run time error 76 path not found, how can use this software?

Digger
31-05-2015, 14:07
hello, when use the drm log plotter a message runtime error 76 path not found,

Hi,
Did you follow the instructions to put the s/w in C:\drmplot?

http://www.hobbyradio.se/en/drm/drmlogplot_en.html#install