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Old 25-08-2013, 17:22   #16
alokesh
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Post details if you have done it .....
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Old 31-08-2013, 10:55   #17
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First try with direct sampling

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.
Attached Images
File Type: jpg C34_2832U.jpg (39.4 KB, 651 views)
File Type: jpg pin_1_ant.jpg (23.1 KB, 718 views)
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Last edited by Digger : 14-04-2014 at 16:15.
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Old 31-08-2013, 15:40   #18
mvs sarma
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Quote:
Originally Posted by Digger
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
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Old 31-08-2013, 16:11   #19
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It might be interesting to feed it from a 455Khz IF thus bypassing the use of 12Khz converter
and sound card.
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Old 01-09-2013, 16:53   #20
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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?
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Old 02-09-2013, 18:24   #21
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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.
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Old 04-09-2013, 09:14   #22
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Quote:
Originally Posted by F1BJB
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.
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Old 04-09-2013, 16:00   #23
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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.
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Old 04-09-2013, 16:16   #24
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Quote:
Originally Posted by Digger
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.
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Old 04-09-2013, 17:57   #25
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Quote:
Originally Posted by F1BJB
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....
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Last edited by Digger : 04-09-2013 at 18:00.
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Old 04-09-2013, 19:57   #26
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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.
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Old 27-09-2013, 16:12   #27
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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.
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Old 03-10-2013, 15:22   #28
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Quote:
Originally Posted by Digger
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
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Old 04-10-2013, 07:37   #29
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Hi
I'm not sure that RF gain is available if you bypass the tuner.
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Old 12-10-2013, 09:00   #30
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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.
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