Any One Here Use a SDR (Software Define Radio) Reciever?

aussieprepper on 06/04/2021 - 16:27

Hey folks just wondering if any one here is into DXing on the shortwave band? I bought a cheap RTL SDR from Aliexpress and my results are average. I am using SDRSharp and the receiver works okay on FM but even on FM its fairly weak.
This is the RTL SDR
https://www.aliexpress.com/item/10000084005143.html?spm=a2g0…

I have a few shortwave radios including a Tecsun PL310ET and a few other cheap radios and they all perform better than the SDR. Any ideas where i might be going wrong?
I use a 13m long wire i connect to my radios and i can pick up stations as far as Spain and Italy with relativity good reception depending on the conditions and time of night. I have tried a few different antennas on the SDR including the 13m long wire and it doesn't help.
I bought a MLA30+ antenna so i could permanently mount it outside but the reception using the MLA30+ is bad even though it is amped. Its using some really thin RG cable 75ohm stuff which i am in the process of changing to RG58 hopefully that will help.

Probably not the best place to ask but of i go to a SDR forum every one from overseas will chime in on how good there antennas work getting a station that is a few hundred kms away. While we here in Australia don't have that luxury as we only have a few active stations.

Electrical & Electronics

Comments

  • RedHab on 06/04/2021 - 17:30
    +1

    Any ideas where i might be going wrong?

    Sensitivity. You've answered your own question.

    These cheap RTL SDR receivers are designed to receive in the 100-700MHz band, not at shortwave frequencies. Even with an HF mixer, you'll have problems, and they also have no image rejection.

    My advice is to look around on the forums, buy a good ham mixer and tuneable amplifier.

    • aussieprepper on 08/04/2021 - 00:45

      Thanks, i will have a look around.

  • bazingaa on 06/04/2021 - 17:56
    +1

    I haven't used one in more than 3 years now and even that I used it in overseas. It was just a TV dongle with RF antenna input, not a fancy one like you have.
    So my knowledge is quite outdated.

    1. There was a patched driver to receive below 100 MHz without any upconvertors, are you using that for SW? With that, you can bypass the RF headend and directly sample from the RTL chip and but you should connect an antenna to the chip inself (by soldering a connector, google for the schematic and more info on the driver). I think this is the way the seller has made that HF input in your device. So, are use using the correct driver ?

    2. You can use an upconvertor to step up 0-60 MHz to higher range (general mixer theory). I think I had one from "Nooelec", can't remember how the reception was.

    3. It was great for all other applications. FM was great (also Analog TV audio as it is FM as well, there was a plugin to watch Analog TV in monochrome too). We made a NOAA weather station at uni with great results with a proper antenna to receive from satellites. It even worked well with the gerenal TV antenna (YAGI) + RF amp for NOAA. I used to receive 145 MHz Ham band from a local repeter as well. I tried to use it for radio astronomy, but the results was not that good (didn't had time to make a good antenna).

    4. This is because, when you amplify the signal, the noise is also amplified. If you amplify it too much, the signal will get distored and the noise level will be on a comparable range. You can see this in the spectrum mode with SDR application.

      reception using the MLA30+ is bad even though it is amped

    5. If you match the impedence at each connection point, there will be a maximum power transfer. This helps greatly when the signal is too weak. I think the input of the SDR is 50 Ohm SMA connector (double check this). So, try to match inpedence at all points to that impedance.

      thin RG cable 75ohm stuff which i am in the process of changing to RG58

    • aussieprepper on 08/04/2021 - 00:50
      +1

      Thanks for all the info i will pull apart the SDR and see what i can do with it. Yea i have tried all the sampling options some work better than others at different frequencies.

      You are far beyond where i am with radios. I built a Yagi for 470mhz CB frequency here it worked okay.

      • bazingaa on 08/04/2021 - 01:39

        don't take it apart. I think they have done it for in your one, just check for the correct driver with the seller.

  • RedHab on 07/04/2021 - 07:12

    Take a look at this instead:
    https://www.sdrplay.com/docs/RSP1Adatasheetv1.9.pdf

    • aussieprepper on 08/04/2021 - 00:52

      I will give it a read , Thanks

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