Tips for RTL-SDR

Discussion in 'Software Defined Radio (SDR)' started by KC8VWM, Dec 2, 2018.

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  1. KC8VWM

    KC8VWM Ham Member QRZ Page


    Use a cheap antenna tuner as a cavity filter of sorts on your RTL-SDR to block out unwanted AM broadcast image trash from showing up across the spectrum.

    Next try out one of those cable TV amplifiers you get for a $1 at a yard sale.

    Despite what the manufacturer specifications say in the literature, these will amplify signals well below 54 MHz. I have one made by Radio Shack that works down as far as 5 MHz. Cheap amplifier solution and a few more dB improvement for your RTL-SDR. :)


    Does anyone have any other tips they would like to share?

    K3RW, N3AWS, AI3V and 1 other person like this.
  2. KA9JLM

    KA9JLM Ham Member QRZ Page

    Have Fun and Enjoy ! :cool:
  3. KB1YFD

    KB1YFD Ham Member QRZ Page

    Here is a mod I did a while back. Modify RTL dongle to RX 10 KHz to 15 MHz. Must be used in direct mode in the software.

    [​IMG] Here is a little project I've been working on. I use the dongle in direct mode. Great RX from DC to 15 MHz.


    Hardware mods: (I removed the caps and connected to the RTL2832U Pins 1 & 2, works better)

    Here is the pic of my hardware mod. It's very small smt stuff. Maybe 10X glasses or a young fella to do the soldering.

    1) Pull cover with fingernails, it will pull apart and snap together when done.

    2) Remove 3 small SMT capacitors
    A) C13 near antenna connector and D6
    B) C33 & C34 near pin 1 of the RTL2832U chip

    3) connect a pair of small wires (AWG 30) to the cap pads that connect to pins 1 & 2 of the RTL2832U chip.

    4) Run the wires over to the antenna connector. One for the shell and the other connects to D6 (See pic)

    5) I use a MCX to BNC adaptor cable to connect to my antenna:

    Go to
    Download the code and unzip it.

    A step by step installation instructions can be found in the community website:
    To get started with SDR# you may be interested by the excellent document from Henry (N2VFL) :

    Plug the dongle into a USB port and wait for windows to say "Found new hardware" when it fails to find a driver, cancel it!

    Follow the instructions located here:

    Have fun and enjoy. It works best at 15 MHz and below. I got WWVB at 60 KHz the other night.

    Best, John KB1YFD
    AI3V, K6CLS and KC8VWM like this.
  4. N2UHC

    N2UHC Ham Member QRZ Page

    I just built a high pass filter which attaches to the antenna input of my converter. I put a switch on it so I can switch it in or out, depending on if I want to listen to the AM broadcast band or not. It really helps to clear up all those lines you see every 10 KHZ on the SDR display.

    I found the filter schematic here:, scroll down to Figure 3.
    AI3V and KC8VWM like this.
  5. K3KIC

    K3KIC Ham Member QRZ Page

    Modern CATV amplifiers have diplex filters to support two way and won't amplify below 54MHz. You need to find the older ones that were designed for apartment antenna systems and not cable.
    These days there are LNAs from China on Ebay for a couple bucks. Much lower noise figure than the older amps.
  6. W5ALT

    W5ALT Ham Member QRZ Page

  7. W5ALT

    W5ALT Ham Member QRZ Page

    Is there a way to get the raw IQ data streams into my PC to process locally and experiment with software?
    Do you know where I can find the interface specifications for these dongles to programmatically access it?I know the SDR# software was open source, but has apparently been withdrawn, so no joy there! Any help appreciated
  8. AA5CT

    AA5CT Ham Member QRZ Page

    A Tayloe mixer and a x4 LO source will do that ... a 4066 CMOS chip (or equiv.) and a couple other CMOS digichips (or 74AC series) comprise the Tayloe mixer ...
  9. KD6RF

    KD6RF Premium Subscriber QRZ Page

    I'm far from expert, but I believe that the IQ data streams are exactly what you get by default.

    I do not know the specs, but do know that HD-SDR does fine with my RTL-SDR versions. I use them both for the IF based "pan-adapers" for my radios as well as for OSCAR satcomm work.

    As usual, there's some random ridiculousness in regard to installing the drivers, but nothing too bad.
    KA9JLM likes this.
  10. W5ALT

    W5ALT Ham Member QRZ Page

    I know that the software like SDR# is accessing the raw data and processing it, but I can't find any information on how to access the traw data fromn my own software. I want to play around with the raw data and do my own experimenting. The first basic step is to find our how to grab the raw I and Q datas from the rtl dfevice.
    I have a Flex 100 which is a basic Tayloe mixer produced by Gerald at Flex Radio. I played around with that and had some fun. It was an amazingly sensitive and selective receiver, but there was no secret to accessing the raw I and Q ata, since it came in on the soundcard input. stereo channels. I'd like to do something similar with the RTL dongles, just for fun!

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