Why Am I Doing This?
1 - To archive bandscans of the FM dial in different places and different times, in an interactive way (as opposed to just watching somebody else tune through FM on a Tecsun via YouTube)
2 - An experiment to see if anybody else is interested, and try and get other people doing the same thing
3 - I'm insane?
A Lesson In SDR
Software Defined Radio, as a lot of you may already know, allows you to see a chunk of radio spectrum and click on signals to tune into them. It also allows you to record the chunk of spectrum to a huge .wav file called an IQ file. I sat in Hyde Park with a portable SDR set up (thin wire dipole, dongle and Win 8 tablet running SDR# which is free SDR software) and recorded about 17 gigs worth of IQ files covering 87.5 to 108MHz. The dongle is a cheap £15ish Freeview dongle, nothing special. The magic comes in the 3rd party 'Zadig' drivers which allow it to tune from 24MHz upwards. There are even DLLs and mods you can do to go lower into SW, and in some cases into MW. These things aren't perfect, they are wide open to problems from images and they have spurs which look like blank carriers and mess up your reception. They are cheap though, fairly portable, and a proper SDR will set you back £100s if not £1000s. So, can't complain really! You can get slightly better SDRs between £100 and £200 which are a bit cleaner, but you might have trouble powering them from a tablet.
It wasn't working it's best during this scan. There is one section of the band that was quite noisy and full of images. That said, I don't think it got in the way of too many stations.
The Files
I've rar'd all the .wav files to crush them down a touch and I've managed to keep all of them under a gig in size. You'll have to unrar them first. There are .txt files with descriptions of the content which are handy if you want to know what's in a file before you download it. The filenames show the time the recording started, and the center freq. of the chunk.
The files are in this folder on mega.nz as I don't know anywhere else that would allow me to store up to 50GB online for free...
https://mega.nz/#F!3UUUnSiD!WLhWZ3ff4f4Pi7Ko_zcodQ
What You Need - SDR# (SDR Sharp) / HDSDR
Install this software first, otherwise you can't play the files.
http://www.sdrsharp.com/#sdrsharp
When the .zip has downloaded, go into it and click the 'unzip' file, it should now unzip itself. Go into the unzipped folder and click the 'install' file, which will then extract the software into it's own folder. SDR# doesn't attach itself to windows through the registry or anything, it just works from the folder.
Alternatively, you can use HDSDR but it's not 100% compatible with the files. It doesn't have RDS built in, so you need to pipe the signal at 192k 24 bit to RDS Spy via VB Audio Cable Asio Bridge. This will give better RDS results than SDR# though.
http://www.hdsdr.de/
http://rdsspy.com/
http://vbaudio.jcedeveloppement.com/Download_CABLE/HiFiCableAsioBridgeSetup_v1007.zip
Link above taken from http://vb-audio.pagesperso-orange.fr/Cable/index.htm
How To Play The Files
Start SDR# and select IQ File (*.wav) from the Source drop-down. It will immediately ask you to locate an IQ wav file to play.
Make sure you tick 'Correct IQ' or you will have a massive spike in the centre of the display.
Snap to 100kHz for easy tuning.
Make sure you have WFM selected.
Press play.
Move the tuner around by clicking / dragging with the mouse and adjust the filter by dragging the edges.
