This is incomplete.

Needs antenna advice
Linux

With recent advances in software defined radio (SDR) it is in theory possible to track and listen into a payload using a £20 dongle and your PC. This is cutting edge and although suitable for testing and tracking the payloads of others it isn't recommended for actual tracking and recovery of your own payload. DVB-T dongles based on the Realtek RTL2832U can be used as a cheap SDR, since the chip allows transferring the raw I/Q samples to the host, which is officially used for DAB/DAB+/FM demodulation.

The RTL2832U outputs 8-bit I/Q-samples, and the highest theoretically possible sample-rate is 3.2 MS/s, however, the highest sample-rate without lost samples that has been tested so far is 2.8 MS/s. The frequency range is highly dependent of the used tuner, dongles that use the Elonics E4000 offer the widest possible range (64 - 1700 MHz with a gap from approx. 1100 - 1250 MHz).

Data sourced from http://sdr.osmocom.org/trac/wiki/rtl-sdr

Gqrx SDR receiver has been successfully used with a the ezcap USB 2.0 DVB-T/DAB/FM dongle with good results.

Data sourced from http://rtlsdr.org/softwarewindows

You will need :

1 x compatible dongle. Author has tested the ezcap USB 2.0 DVB-T/DAB/FM dongle with good results.

When you plug in your dongle Microsoft may install some drivers however we are going to replace those. Firstly install the latest version ZADIAG from here :

http://sourceforge.net/projects/libwdi/files/zadig/

Its in a 7zip format so you will need to get 7Zip to extract it.

Run zdiag.exe and you will see the following with an empty list :

Click on options and select “List all Devices”

Choose the one that says “Bulk-In Interface (Interface 0)”.

In the box on the right of the green arrow ensure WinUSB is chosen. Check the USBID matches one of the devices in the list above. Click the button that says “Replace Driver”.

There are many SDR programs out there for this example I'll be using SDR# ( http://sdrsharp.com/ ) due to it being quite simple to operate. Download the latest DEVELOPMENT version from here : http://sdrsharp.com/index.php/downloads and extract it somewhere.

Due to some licensing drama you need to do a few additional steps to get RTL based dongles working.
Download the pre-built Windows RTLSDR Binaries from Osmocom.
From this zip file extract :

RelWithDebInfo.zip\rtl-sdr-release\x32\rtlsdr.dll
RelWithDebInfo.zip\rtl-sdr-release\x32\libusb-1.0.dll

Placing them in the same directory as you extracted SDRSharp.

Now edit SDRSharp.exe.Config in a text editor and amend this line :

<!-- <add key="RTL-SDR / USB" value="SDRSharp.RTLSDR.RtlSdrIO,SDRSharp.RTLSDR" /> -->

so it looks like this :

<add key="RTL-SDR / USB" value="SDRSharp.RTLSDR.RtlSdrIO,SDRSharp.RTLSDR" />

Added 07/09/12 Kevin Walton. As of the 07/09/12 the latest Dev versions of SDRSharp now also need the following:

• Download the SDR# RTL Plugin and copy the contents contents of the zip file to the SDR# directory.

• When I copied the contents of the zip file into the SDR directory, it asked me if I wanted to overwrite several files - I said yes to overwrite all files and SDRSharp works.

Run sdrsharp.exe and you will see the following window:

Check WFM
Next to front end drop the box down and select RTL-SDR / RTL2832U
Next to center type 98,000,000 (enter)
Press Play

If you have it selected correctly you will see something like the following. Each of those yellow and red lines on the waterfall are commercial FM radio stations. Put your red cursor over one and click. You should be able to hear the station.

Due to the huge bandwidth of the dongles you can seem pretty much the whole frequency range the payloads operate on in one fell swoop, however sometimes this does make locating the payloads in all the noise difficult.Amend the centre frequency of the dongle to 434,500,000 and the mode to USB.

You should now see something like this :

Now turn your payload on. You should see a spike around the frequency of your payload :

Click near to this with your cursor, then zoom in slightly, the reposition your cursor over the top of the peak (in this example I've increased the filter bandwidth to 4000 as well) :

At this point you should be hearing the RTTY from your payload. You can zoom in / amend filter bandwidth to get it spot on the frequency. You can expand FFT Display and increase the resolution to make the waterfall and spectrum analyser less blocky.

For the next step you will need to download and install Virtual Audio Cable or some other such software.

Virtual Audio Cable is available here : http://software.muzychenko.net/eng/vac.htm

Jack Audio is availble here : http://www.jackaudio.org/

Install it and just accept the defaults. Now go into Control Panel → Sound → Recording.

You should see an input called Virtual Audio Cable, click properties and rename it to SDR. Click on listen and check the Listen to This Device option :

Stop SDR# and under Audio select Output Line 1 (Virtual Audio Cable) Click start, you should now be able to hear the payload still.

Now open DL-Fldigi, click Configure → Sound Card Click Capture → SDR(Virtual Audio Cable)

You should now be able to click on the payload as normal and decode :

Installing the new driver will stop the EZCAP from being seen by the supplied radio/TV software. The quickest solution is to just plug it into a different USB socket when you want to use it for that, and re-insert in the original socket for tracking.