Noise canceling with RTL-SDR adapters
Yesterday someone pointed me to this video where G7CNF Nige uses two receivers and the Diversity feature in PowerSDR to phase out noise from the receiving signal. Now, cross-phasing has caught my interest when i came back to the radio almost two years ago because of the PLC noise i have in my shack. Nige is using the two receivers in his ANAN-100D, i don’t have a device like that. Also i think it’s much “cooler” to try to do this with RTL-SDR adapters.
PowerSDR is made for the Flex receivers, but there is an OpenHPSDR version of PowerSDR. Then N1GP wrote a bridge from SDR_RTL to the HPSDR platform. So using this bridge i should be able to access my RTL-SDR adapters using PowerSDR. Let’s see if that works.
- Get a separate Linux machine to run the bridge on.
- Get your dependencies installed to compile the bridge. In my case (fresh Ubuntu 12.04) i needed to install build-essential, git, cmake, libusb-1.0-0-dev, libasound-dev
- Clone the sources for the bridge. Do not use the branch mentioned above, if you read the README there you see that you need to use:
#git clone https://github.com/n1gp/librtlsdr.git
#sudo make install
- You should now get something like this:
rtl_adsb rtl_eeprom rtl_fm rtl_hpsdr rtl_power rtl_sdr rtl_tcp rtl_test
rtl_hpsdr is the one you want!
- Connect your RTL adapters to the computer and test rtl_hpsdr:
#rtl_hpsdr rtl_hpsdr Found 2 RTL device(s), using 2. RTL base sample rate: 1536000 hz Global settings: config file: none ip address: 127.0.0.1 length of fir: 32 number of rcvrs: 2 hpsdr output rate: 48000 hz sound device: none Rcvr 1 (ordered as 1) settings... freq offset 0 hz signal multiplier 1 Found Rafael Micro R820T tuner tuner gain auto Disabled direct sampling mode direct sampling off agc mode off Rcvr 2 (ordered as 2) settings... freq offset 0 hz signal multiplier 1 Found Rafael Micro R820T tuner tuner gain auto Disabled direct sampling mode direct sampling off agc mode off Revealing myself as a Hermes version 2.6 rcvr. My IP Address: 127.0.0.1 My MAC Address: 00:00:00:00:00:00
Nice, rtl_hpsdr is running and we found two RTL devices. Notice the last lines, they are important. “Revealing myself as a Hermes version 2.6 receiver” and the IP and MAC address of the server. Remember those two.
- We are almost done on the server side. The only thing that is left if to start rtl_hpsdr listening on an IP address that we can access from outside. We use the -i option for this. I suggest you enter at least once “rtl_hpsdr -h” to understand which options there are and what they do.
#rtl_hpsdr -i 192.168.1.20
- We are done on the server side. Now let’s install PowerSDR on your Windows workstation. Download PowerSDR from http://openhpsdr.org/download.php and install it. Nothing special, just a standard Next, next, Finish.
- Remember that rtl_hpsdr told you it presented itself as a Hermes receiver? So in PowerSDR make sure that you select the Hermes receiver. Leave the Connection type to Hermes and Full Network Discovery.
Now you are ready to start PowerSDR and connect to the Hermes/RTL-SDR server. When you are connected the IP address of the server should be displayed in the Hardware config screen.
There are a couple more things to take care of. The Hermes transceiver board covers a frequency range of 50kHz-55MHz. The RTL adapter covers, without up-converter, 24-1800MHz. So the only usable frequency range with this combination is 24MHz (lower side of the adapter) till 55MHz (upper side of the Hermes). You can extend that range a bit by using the HPSDR cinfig panel, but more than 150MHz it will not do.
If all is working fine you should see someting like this on your console:
You can now activate the second receiver as well by clicking on the RX2 button next to the power button and then select the Diversity menu item.
Personally i found PowerSDR highly unreliable. I don’t know if it’s my PC, the communication between the PC and the server or the quality of the server, but in my install PowerSDR locked up every time i wanted to use it. It’s partner software cuSDR turned out to be more reliable, better looking as a panadapter, but lacks the Diversity function.
Let me know what you think of this article and let me know if you have more success than me setting this up.