The usual DRM solutions require a modification of the receiver. But this will cost some money and if you only want to get a short impression of DRM there is a better solution.
What you need is:
- a PC with 2 soundcards
- a scanner with SSB and IF filters wider than 10 K
- DSP software like SR5 (free)
- DRM decoding software like DReaM (free, compiled)
- If you cannot find the compiled version under that link ask Google
The AR5000 must be set to:
30 K bandwidth
10 KHz (Shortwave) or 9 kHZ (Medium Wave) below the center frequency of the DRM transmission (6085 for RTL)
Connect the AR5000-Phones-Plug with Line-In of soundcard#1
Connect the output of soundcard#1 with Line-In of soundcard#2
Connect the output of soundcard#2 with the speakers (phones, home stereo or whatever you like)
Start SR5 and configure the settings:
Tools > DSP and other settings > Highest frequency must be 22.050
Tools > Setup Audio Devices > choose soundcard#1 for in- and output and "line" for source
Start processing (F12 or )
Use Filter (F2 or )
Toggle filter window (right click on )
Shape out the DRM signal in the filter window while pressing the left mouse-button
Now the signal is digitally pre-filtered.
You can start the DReaM software now.
It must be configured for soundcard#2. (Settings > Sound Card Selection)
Adjust volumes with both sound card mixers to improve the signal quality.
I could decode strong DRM signals like Deutsche Welle, Radio Kuwait, RTL, VoRussia and BBC over most of the time with this solution, using an average PC (2 GHz). Once a minute the signal usually interrupts, but it comes back again.
Watch the SNR (View > Evaluation Dialog): Values of about 10dB are required for a station ID, 15dB is necessarry for audio reception. I rarely got an SNR of more than 20 dB.
Some experience: No problems were caused by
Surprisingly, there were no big problems with heavy noise caused by an electric fence close to my antenna.
Two DRM signals close to each other (5800-5810 and 5810-5820 KHZ) don't cause problems
Big problems with unwanted carriers:
Any interfering carrier will lower the signal quality rapidly.
notch that carrier out with the SR5 software:
Some carriers apprear from the other side band. Vary the frequency!
15 K bandwidth
This filter works when you use only a spectrum like 0-10 KHz and boost the higher frequencies:
Questions? Corrections? Ideas? Comments?
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