RTL-SDR - an SDR receiver from a cheap DVB-T tuner on a USB connector

Install these drivers https://www.elektroda.pl/rtvforum/topic2353101-360.html#14390448, I was calmly receiving 5Mhz transmissions (but they were strong stations). I noticed that around 11MHz the tuner system stops working and only the ADC works. Suddenly (abruptly) the signal level drops significantly.

I will check it in a moment. It seems to me that the new drivers do not unlock the head at lower frequencies, but switch from the machine to direct sampling and use the "puncture of the signal through the bone".

Which is, of course, 5 seconds to show. You go through this sensitive point and touch the adc pins with a needle, when the signal jumps in value, you know when it appears elsewhere, the transformation works.

mkpl wrote:

Which is, of course, 5 seconds to show. You go through this sensitive point and touch the adc pins with a needle, when the signal jumps in value, you know when it appears elsewhere, the transformation works.

I touched the ADC pins with a needle, but it didn't change anything. I touched both before and after the condensers.

I analyzed both screenshots you posted. Unfortunately, both look like interference from the FM band.
Were you able to pick up something?

At the time of taking screenshots, no. I did them only to show the decrease in signal strength (without the antenna). However, much earlier, when I connected a long cable (about 15m) to the hot wire and grounded the screen, I calmly received radio stations on 5MHz modulated in AM. These were, of course, foreign stations. https://obrazki.elektroda.pl/3804903500_1428088459.png

In addition, on 17Mhz I also receive AM stations.

You convinced me. I am going to get the tuner and I will test it

I noticed that with these new drivers, the 5Mhz reception was supposed to improve, the tuner is not as sensitive as it should. I changed the dongle by completely cutting off the signal from the head. I ran the signal straight from the antenna through capacitors on the RTL2832. Of course, the mass paths to which the antenna socket was soldered had to be cut so that the rest of the system would not wake up. I set "Direct sampling Q-branch" in the SDRSharp settings and I receive signals from 1MHz to 28Mhz on a 1.5 meter vertical antenna. The photo shows the connections. Of course, such a converted dongl is no longer suitable for receiving the band above. There are descriptions on the net how to do it, you can also use a choke, but I gave it up because it lowered the sensitivity.

don_viking IMHO pity the tuner Something else like the head layout burned or something. BTW. since you are modifying the tuner in this way, try to connect the output of the head chip to the sound card (remember to connect the tuner to the power supply).

For me, Direct sampling is not working. After changing the settings, the program throws an error when you try to press the play button.

You are right, I decided to convert the dongle because I accidentally fried the E4000 head and therefore instead of throwing it away I changed it. Because of them, I made a short circuit at the antenna input and 12V went there. Therefore, when someone has such a damaged tuner, he can successfully use it as a HF receiver. I don't know what program and what dongle you are using, but I have LV5TDLX, the kf one on the E4000 and for the higher band I use the same dongle only on the FC0013. I also have one for the R820T, but I don't test it that way and I use the band above 1Ghz to receive it. As for the program, SDRSharp and HDSDR. I turn on HDSDR using the driver in the attachment.

When I gave 12V to the input, I only burned the protective diode. Everything works (without the diode ). At the antenna input I have a capacitor in front of the head, so 12V will not go there anyway.
As for the reception above 1 GHz, any converters, is it just spinning? Has anyone been listening to 2.4GHz? :)

Except for the topic, this is how the 10Ghz band looks like, I connected to the LBN out of the sat decoder (working).

It just so happened that I burned the head and two capacitors fired near it. I don't have a converter, but maybe I will connect something one day.

I wanted to show off my successful modification of the SDR

I removed the sockets (the usb was factory defective anyway) and the IR receiver because it was unnecessary anyway

The housing is a BADMOR signal splitter (it fell into my hands and the sockets fell apart).

A cable from some telephone (the use of a shielded one lowers the noise).

To sum up. By default, the gain was set to 12.5dB to get noise around 55dB (I live in Mysłowice and have 5km to the transmitter in Costowy ...),

Currently without antenna -60dB noise at 42dB gain! Revelation!.

I did not get such effects even by shielding the dongle housing with aluminum foil and by placing x ferrite cores on the USB cable.

Interesting modification. I see my friend has some other SDR (square one) and with a resonator instead of an oscillator. The foil screen does nothing in my case. BTW. SDR works fine for me with a laptop, a desktop PC sows terrible.

I have a tuner like this:

[img]
https://obrazki.elektroda.pl/1408081000_1324724991.jpg[/img]

So rather typical. The housing only says "DVB + DAB + FM"

tomek10861 wrote:

and with a resonator instead of an oscillator.

A mistake, a colleague is with the generator, instead of the resonator itself.

That's exactly what I meant I just wrote something else In any case, it is worth giving such a generator to a purchased tuner? How's the frequency stability? Holds on regardless of the temp or floats?

Man, I don't know, I'll check.

Generally, when the tuner heats up (and it does it quickly and efficiently) it is practically stable as a frequency standard.

Such parasitic OCXO

This is the first time I see a Media Tech tuner with the R820T tuner. Typically, IT systems are installed there, e.g. IT9135 and IT9137. A colleague may give the model symbol of this tuner, eg MT4166.

I expressed myself badly, the housing is only similar.

I haven't been able to find anything like mine on the internet ....
So I throw in a photo of the case

So you have something else. It is a cheaper version of the tuner from NooElec.
http://www.nooelec.com/store/nooelec-nesdr-na...l2832-r820t-w-antenna-and-remote-control.html
This tuner of yours is available on the Allegro for about PLN 55.

It was sold on alledrogo as a typical SDR, the guest even tested a band or something for about PLN 70. I don't remember any more because it was a year ago .

However, all these tuners are patched on one diagram, so I do not see a problem to duplicate the modification.

Yesterday evening, during a creative conversation with one of our colleagues, we came up with the following housing:


Copper tube for CO (under the width of the pcb), two "plugs" and a 2mm copper flat bar.


Cut the flat bar so that the tuner fits on it and is the entire length of the tube. Then we clean it of oxides and put a thick thermopile on which the tuner will lie. The mounting of the tuner itself is as simple as possible, i.e. the silver plate soldered from the bottom of the flat bar and to the ground on the tuner pcb so that it presses it firmly against the thermocouple.

One of the ends of the flat bar is soldered to the plug with an SMA / BNC socket, and to the other plug, a USB socket such as "printer". Now you just need to put everything together and we have a nice durable SDR



Rectification:
Shielding significantly reduced noise, etc., a revelation, but thanks to cleaning the signal and the tuner environment, you can now see other undesirable effects. A weak "carrier spectrum" appeared - signals coming from the computer and propagating through the USB cable. In days I will make a coupled choke and describe the results.

Hello, I bought the R820T2 usb scanner through alledrogo, along with the telescopic antenna for the broadband scanner BNC is about 110cm. And got out. I controlled this whistle, supposedly active on sdhrd, sdr, etc., but you can not hear anything at all, even a commercial radio on 107.7 fm with distortions barely, barely 1 station, audible only when I set the sampling very high and this strong radio from Toruń is known what because I'm about 20 km from Toruń. I did an experiment - put the laptop next to the cb radio, set the frequency, modulations, the spectrum seemed to respond, but the voice was barely harshly mumbling something there. The antennas next to each other, i.e. the CB and the telescopic antenna, were about fifteen meters apart. Antenna screwed on properly. I flew through the instructions, tests, even instructions on you tube. I do not get it. Will someone drive? Or he knows what it is about. And he doesn't want to expose the visitor to the negative, as they say; ignorance does not exempt from responsibility ... because maybe there is a procedure that will make it not junk, but an efficient invention of this Finnish man. best regards

Enter the tuner options and set the sensitivity.

I will say this: radio stations caught clean, what I do not know, I also have a question: wfm and nfm, squelch is active with nfm, is it just the difference, and this is the same fm? The second thing on hdsdr does not work, but the stations started after the setting you gave me on the screen on the sdr sharp.

WFM - wide fm. NFM - narrow FM. FM is frequency modulation, which means that the transmitter detracts a bit, and AM is amplitude modulation (that is, transmission power regulation). Thus, this frequency modulation can be wide or narrow. Squelch is active - you can turn it off however you want. What can you listen to? Catch my video (maybe the admin won't get upset )

For the test, fire around 930Mhz, you should hear GSM.

tomek10861 wrote:

Except for the topic, this is how the 10Ghz band looks like, I connected to the LBN out of the sat decoder (working).

I think that the effect would be better if you connected this DVB-T dongle through the separator directly to the converter. Remembering that you would need to supply the converter with voltage of about 12V (writes sat on the back of the tuner) through this separator. Then in the band between 900Mhz and 2200Mhz you should be receiving the satellite signal. Converter - what is it? Satellite converters are devices used to shift and amplify signals in the ranges 10.7 - 11.7 and 11.7 - 12.75 GHz in the range of the first intermediate satellite frequency (950 - 2150 MHz).

don_viking wrote:

I think that the effect would be better if you connected this DVB-T dongle through the separator directly to the converter.

Separator needed? I will do some research, but at 10GHz, apart from satellites, there is nothing interesting

You need a separator, because the LNB requires a power supply, and the polarity is switched by voltage. 14V - vertical, 18V - horizontal

And so, what I was supposed to burn on the tuner, I burned it (giving voltage without a separator to the TV antenna).

I tested USB filters today. In general, the effects are interesting, I put them in the attachment.

The tests were performed on one frequency (the largest muck) with a Sample Rate of 2.4 MSPS, RTL AGC and RF Gain turned off 49.6 dB and the antenna disconnected.

But I am worried about another matter. These crap are due to the USB extension cable that I use with the tuner.

After making your own cable with an appropriate shield, the problem was 10 times less visible at the beginning, but in general the filters I recommend do the job.

Execution:
"Bead" cores such as are sometimes applied to the legs of the elements. For USB, it is a 2x 0.25mm winding wire pulled 2 times (2 coils) between D + and D-, the second choke is 4 coils on the same core, plugged into the positive power supply rail. I didn't plug anything in the negative rail because it caused the tuner to hang ...

Generally, the inductance of the coupled choke for D + and D- is about 5uH (for 40MHz it gives an impedance over 400OHm). The power supply choke is 6.5uH (for 40MHz it is about 600OHm).

In my free time, I will also experiment with the capacities between the power supply and the screen, it may allow to reduce the inductance, which will ensure greater resistance to strong interference signals (communication likes to crash when turning on a high-power device, e.g. microwave).