Getting Your RTLSDR Online Using OpenWebRx

Over the Christmas break a few like minded folk including myself monitor and share each others HF/VHF comms of the Sydney To Hobart Yacht Race (S2H) via the internet.  This year we were missing someone to help cover the NSW south / mid coast. Searching the web I stumbled onto "SDR.HU" which has a heap of online KiwiSDRs plus a few RTLSDR online and free to access.  (Note: the KiwiSDR project has forked code from a project known as "OpenWebRx").

The KiwiSDRs allows a bandwidth of 30MHz which covers the HF spectrum and allow (depending on processing power) up to 4 concurrent users to each have a virtual RX and tune to any frequency within the 30MHz.  This is a fantastic feature as most other online receivers  either only a single user can tune the spectrum (ie GlobalTuners), or most of the Multi user WebSDR ones are fixed to a set of bands usually the Ham bands which means does not cover the 4483 / 6516 kHz which are the frequencies used during the S2H yacht race.

On the SDR.HU site there was about 6 online KiwiSDR's online located in (SA, VIC, NSW and TAS).  Fortunately 2 of the Kiwi had fairly good antennas connected and in good locations:

1. SDRTAS - Launceston, Tasmania
2. Tecsun Radios Australia - Goulburn NSW

The Tecsun KiwiSDR was fantastic and we had great coverage of the start of the race until the yachts got near Bass Strait / Tasmania were the Tasman KiwiSDR and our groups coverage took over.

For Christmas Santa had brought me a SDRPlay RSP2Pro and I loved the idea of this this online, so I took a look at what was involved and had it online fairly quickly.  This post is not about the SDRPlay and I'll cover that in another post.  This post is about getting your RTLSDR online.  You do not need to register it under SDR.HU if you wish to have it private, but why not! the more the merrier right!

Even thought you the bandwidth of the  RTLSDR is around 2.048 MHz (without too much stress on CPU or loss of quality) and  if like me you have more than one it can put each one online and provide coverage of  a single large or even multiple band segments.

There are many useful HOW-TOs out there that can get you quickly up and running such as:

1. Getting RTLSDR and OpenWebRx installed and running.
2. Compile and installign SoapySDR and SoapyRTLSDR libraries and utilities.
3. Compile and install RX_Tools and SoapySDR 

From the above sources of HOW-TOs I've put together a single script / set of commands that is needed to install the (Development Tools, OpenWebRx, Rx_Tools, SoapySDr, SoapRTLSDR etc)

Download - "install_openwebrx_rtlsdr.sh"

Testing RTLSDR device

Once you have installed the necessary libraries etc, you can now plug in your RTLSDR(s) .  The following are example commands to (find / probe) the RTLSDR dongles.

rtl_test -t

SoapySDRUtil --probe

SoapySDRUtil --find

If you do not successfully see your RTLSDR listed, then please go back over the HOW-TOs and my script to see where the error may have occurred or step omitted and apply corrective actions.

Setting up OpenWebRx

If you have used my install script there is a folder "~/sdr/openwebrx" which contains the OpenWebRX project.  You can copy / clone and rename as many of these folders as you need for each RTLSDR you wish to run.

I will not be going into any detail about each of the config items but I have included two versions of the config files that I use when running my 2 RTLSDRs on the same PC.

1. NooElec (see photo) - config_webrx.pl (configured to Monitor UHF Satellite and Repeater Output segments 436.9 - 439 MHz) 
2. UV_HF (see photo) - config_webrx.pl (Configured to Monitor VHF Marine Simplex 156-158 MHz)

(FYI: I actually originally wanted to monitor the whole UHF Ham Satellite and Repeater Ouput 435 - 439 MHz but the UV_HF seems a little deaf on UHF even with the RF gain set to 49.6, note to self get another SDR to replace the UV_HF. On another note and not to be greedy, but another RTLSDR (or SDRPlay) would nice to monitor the Maritime Repeater Output between 160-162 MHz)

What I will make note of is that in both config files the "rtl_sdr" and "rx_sdr" config sections are valid and working.  I do have them currently on "rx_sdr" as I like it better because unlike the "rtl_sdr" were I can only specific a device number via the "-d" option, the "rx_sdr" allows you to specify a query so in my case its the "serial number".  This means if I unplug one of the devices the correct devices will be found and the issue of the ordering device number changing does not come into play.

Helpful hint: Tor working out what waterfall max/min level values to use go via your browser hit the button to auto-adjust the via the browser debugger looks at the values stored in "waterfall_min_level" and "waterfall_max_level" and update your config file accordingly.

That's all folks!! Hope the above get you online and sharing your RTLSDRs!
73
Mark (VK4TMZ)