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

mkpl wrote:

You have too high a gain value and therefore the background obscures the signal.

Uncheck RTL AGC and Tuner AGC and set the gain to the minimum and increase it until the background noise slightly jumps so that it does not exceed -50 to -55dB and you should hear more.

Has no effect

This is the question of the antenna. Increasing the gain only spoils the signal / noise ratio. You will receive the same according to the formula I gave in the previous post and further increasing the gain only increases the noise.

You can make the antennas as using the original base to which you wind the appropriate length radiators soldered to the pcb distance or if you have the option to buy "tubes", for example in a Praktiker with the appropriate diameter + threading (length according to the pattern and shortening factor).


As a comforting argument, I will add that with a factory radio and a 2m antenna in my location, I sometimes receive better stations 200 km away than stations less than 20 km away. It's all about the propagation and "shadow" of the radio.

czifeng wrote:

mkpl wrote:

You have too high a gain value and therefore the background obscures the signal.

Uncheck RTL AGC and Tuner AGC and set the gain to the minimum and increase it until the background noise slightly jumps so that it does not exceed -50 to -55dB and you should hear more.

Has no effect

You receive digital DMR modulation (MOTOTRBO) I wrote about it earlier in post 711 but nobody reads it, only everyone writes more posts, I even added a sample in post 734 for sound comparison. And change the modulation to NFM because in the photo you have AM and therefore you have noise instead of the normal modulation that is used in this particular band. As for these wide, evenly spaced vertical stripes, it's noise from the computer. Try to connect to a different port and preferably through an isolation cable. I am about a meter long and well shielded, away from power cables. But the basic thing, as a colleague wrote above, do not give full amplification and turn off RTL AGC and TUNER AGC.

Thank you for your help

These Chinese radios are practically the same as sdr but with a receiving amplifier and the ability to transmit. You can see the whole band and you know who is talking where on the monitor, and he can only turn on the scanner and wait when it stops somewhere. I do not recommend these Chinese toys. But I recommend buying an antenna amplifier, eg FP6L works from 5MHz to 2400MHz or the SWA9701 antenna amplifier. I have both and find both of them working great. You connect the amplifier between the tuner and the antenna through a separator, of course, if the antenna is not short-circuited, i.e. the antenna's ground is not connected to the radiator. You power around 12V and the tuner works better for you than this Chinese toy. Of course, then the gain in the program is reduced to 1/3. For the 80MHz to 900MHz band, I recommend SWA9701, and above FP6L, but the FP6L puts the voltage on the antenna, so below I described the connection sequence depending on the type of antenna.

The antenna is short-circuited

1.Antenna electronically short-circuited
2. Antenna separator without power supply
3. FP6L antenna amplifier
4. Antenna separator powered by 12V
5.Tuner

The antenna is not short-circuited

1.Antenna not short-circuited
2. FP6L antenna amplifier
3. Antenna separator powered by 12V
4.Tuner

The best amplifier is an antenna. Putting amplifiers into RTL is asking for trouble. This is due to the lack of bandwidth filtering at the SDR input.

For example, we assume that we receive e.g. 145MHz and set ourselves to the maximum sensitivity for this band. The sensitivity will come out within 0.5uV and the overload is 20uV (theoretical values) and now by connecting the broadband antenna to the amplifier we have theoretically better signal, but when something next to it is strong, e.g. RMF on 93MHz will enter the input with a signal strength of 30uV, then after the short circuits. Nothing is picked up by a distorted tuner and chaff on the band or permanent noise.

In this invention, absolutely everything goes into the head, there is no bandwidth cutting and attenuation, so it is important to work with a good antenna or make appropriate bandpass filters for the sections of the band we are interested in. Then the RTL amplification does not generate such a mess and the noise is much lower.

I used several tuners on different E4000, FC0013, FC0012 and R820T2 chips. For about 3 years I have been testing these tuners on amplifiers and I make various antennas for the bands from 50MHz to 2GHz. I will say one thing, if you know how many gain you can set and in what band, you will never overdrive it. One must know moderation in everything. I know that without these amplifiers, I would receive maybe 1/3 of all signals I receive now and I have no problem with clipping. If you live like me in a block of flats, you don't have a lot of choice when it comes to antennas because there is no place to mount them.

The problem is that I receive the 127MHz band from a distant city +/- 30 km, while from my city zero ... all gain off (RTL, AGC, TUNER AGC, RF Gain to zero. When the signal appears, it is immediately very strong, so 'compact' The zoom, range, contrast, RF adjustment is for nothing. The antenna has been shortened to 41.5m and still catches the 130MHz band very well. Thanks in advance for your help.

From what you write, you listen or want to listen to the airport, because 127MHz is the air band. This is when you set the AM and you have a different frequency. Below you have a link to the page with frequency.
http://lotniska.dlapilota.pl/kielce-maslow

Write to me at PW what amplifier are you interested in and we will continue the topic there.

I have a question, has anyone ever tried to connect similar 2.4GHz tuners? Once in the movie I saw someone using a similar tuner from surveillance cameras to receive the L band.

Will copper tubing have better reception than 2.5mm copper tubing? Because I do not know if I should make a new antenna from pipes and what about this frequency scan anyone have any idea?

czakos wrote:

Will copper tubing have better reception than 2.5mm copper tubing?

Generally it makes no difference. If only mechanically grasped it, it would not break or deform under its own weight.

Damn because I bought tubes hoping that the reception will be better than the wire from the electric cable and, of course, the broomstick, because the stick would not be able to withstand it tomorrow I will post photos after I put it together. Anyone know where in the block I can install the antenna? Because I have a balcony on the balcony, but the blocks form a horseshoe, so I wanted to throw it on the roof, but it is too noticeable. I ordered 9 m of cable and I want to throw naked on the chimney above all the blocks because she is not so conspicuous

They once taught me that the larger the diameter of the tubes, the wider the dipole works, but I have no physical explanation for it.

czakos wrote:

and, of course, the broomstick, because the stick would not be able to withstand it

A broomstick? Better to use the tubes.

internick wrote:

They once taught me that the larger the diameter of the tubes, the wider the dipole

They taught well, but on the reception it doesn't matter. What else, if you wanted to broadcast, you will immediately see the difference.

internick wrote:

but I have no physical explanation for that.

The larger diameter of the radiator represents a larger capacitance. Generally, the L \ C ratio of such a radiator changes.

Hello gentlemen, on Sunday morning I decided to go to work after yesterday's shopping, for comparison, I attach photos of the previous antenna made quickly And here, to my surprise, this 1 structure received much better reception, I mean it also receives a much weaker signal and maybe I have a higher gain on this one, I have 8.7 dB. From what my colleague Kamilo noticed that he has just behind the can, such as a coil made of a wire, maybe this is the reason? It seemed to me that thicker tubes had more copper surface to receive
The last two photos, the 1st construction, the next one, is the 2nd construction, I will add that the tubes are 50 cm long and the 1st construction is 48 cm, which is typical for the strip. It is mounted exactly in the same place and yet the reception is worse and I suppose the distance is probably shorter, but after 15 minutes it's hard to say.
I checked with a meter and the transition is from the tube on the plug and there is no short circuit.

czakos wrote:

.. maybe I have a higher gain on this, 8.7 dB ...

I have 42 dB and then it receives almost the same as the Uniden BCT15X.

Condition? No distractions, otherwise there will be chaff and kociokwik.

But on the wire I had 7.7 dB and it collected better, and how many can you go up so that nothing will happen to the tuner? Kamillo, I ordered baofeng when I test, let me know: p

Solder a 1k resistor or a 100uH coil between the tubes (better a coil). The antenna is open and must be shorted for DC to protect the tuner.

The thickness of the tube determines the slenderness of the antenna, i.e. its bandwidth, but this parameter goes hand in hand with the shortening factor, which should be taken into account for the antenna to tune in the assumed band.

Hello

I wanted to ask what core these transformers should be wound on? I have a T37-2 (red)

I see. For the latter, I have all the parts. How to expand it to All right walked on short waves.

In the second diagram, cores from television baluns are written, the closest material is material no. 43 from Amidon.

OKAY. But they are quite expensive these Amidones ......

Will the ferrite from the SYM-02 antenna balun be good?

PLN 3 a piece. And this SYM 02 is made of what material it is made of.

RAFPOL5 wrote:

In the second diagram, cores from television baluns are written, the closest material is material no. 43 from Amidon.

You mean FT50-43

Would anyone be able to write about the differences between the following receivers and which one is best to order?

100KHz-1.7GHz VHF UHF Band RTL.SDR + UpConverter SDR Receiver NFM FM DSB LSB CW
http://s.aliexpress.com/BFBNRvEz
(from AliExpress Android)

100 KHZ - 1.7 GHz all band radio RTL - SDR receiver RTL2832 + R820T RTL-SDR
http://s.aliexpress.com/quUZNFfa
(from AliExpress Android)

NEW 100 KHZ to 1.7 GHz all band radio RTL - SDR receiver (RTL2832 + R820T) + long-antenna + balun 9: 1
http://s.aliexpress.com/bmaQR3UR
(from AliExpress Android)

After all, this is the same crap as shown several posts earlier - a regular DVB-T tuner for RTL2832U + Direct Sampling modification in the set with Nagoya UT-102UV.

Ok, but I'm interested in what exactly is the difference between these 3 receivers

I know that 2 are identical and differ only in that one has a long-wire added for which you pay about $ 12
However, I am interested in what is the difference between the receiver for $ 40 and $ 60.
If this ....... then what is the best sdr receiver to buy?

There is not much choice with the R820T2 chip. You can pay extra or not to TCXO.