How to Create a Linear Transponder using a RTL Dongle and HackRF with Gnu Radio.

How to Create a Linear Transponder using a RTL Dongle and HackRF with Gnu Radio.

I wanted to test the concept of a linear Transponder and how difficult would it be to build it with conventional components.

Hardware Configuration

Hardware required to build the Transponder.

1. SDR IQ demodulator with rtl dongle (RF In)
2. SDR IQ DSP processing system. Gnu Radio (DSP processing)
3. SDR IQ Modulator. HackRF (RF Out)
4. Background management system. (OBC) for additional telemetry.

Software required for Transponder.

1. SDR IQ demodulator. rtl dongle (RF In)
2. SDR IQ DSP processing system. Gnu Radio (DSP processing)
3. SDR IQ Modulator. HackRF (RF Out)
4. Background management system. (OBC)

Video of working Transponder.

Gnu Radio.

Transponder Block Diagram

RTL SDR Block.

RTL-SDR Source

Low Pass Filter Block.

 

Low Pass Filter Block

AGC Block.

AGC Block

Power Squelch.

Power Squelch

Osmocom Sink. (HackRF)

Osmocom Sink (HackRF)

FFT. (Spectrum View of input)

FFT Spectrum View

REF: Power point Slides at AMSAT SA

Ref:Source code is available on Github Version 4

Creating a 2m Fm Repeater with a Raspberry Pi (B) and a RTL dongle.

Creating a 2m Fm Repeater with a Raspberry Pi (B) and a RTL dongle. (Don't use this application without the RF filter)

RTL dongles is available from Giga Technology and the filter will be available soon.

For the purpose of this configuration I expect your Raspberry pi to be connected to the internet.

How will this repeater work.

This configuration was done with the latest Raspbian Os for Raspberry Pi downloaded from here https://www.raspberrypi.org/downloads/

I used my original Raspberry Pi B+ and also repeated  this on a Banana Pi

 as I need a hard drive to compile gnuradio for later SDR use.

I will be using a rtl dongle to receive my input signal on 70cm frequency configurable on the amateur 2m or 70cm band. The receiver signal will then be demodulated and re transmitted with a DSP Library simulating a FM Signal using a GPIO pin on the Raspberry as an transmitter.

Get your Raspberry Pi on the latest patch/update.

sudo apt-get update

sudo apt-get upgrade

Go and get some Coffee as it might take long time to update ..zzz...... ;-) 

Install the SDR command line application to access rtl  USB dongle.

This rtl library allow you to demodulate the fm / ssb input

sudo apt-get install rtl-sdr-0.5.3-3 mplayer octave gnuplot gnuplot-x11

Download the Fm transmitter software from github using the following command

Install the rpitx python library using the following command. 

rpitx is the main software to transmit. It allows to transmit from:

• IQ files *.iq (can be generated by external software like GNU Radio).
• Frequency/Time files *.ft (generally used to easily implement digital modes)

Installation of rpitx

git clone https://github.com/F5OEO/rpitx git clone https://github.com/F5OEO/rpitx

cd rpitx # make sure to have access to the internet to download packages # or download and install them manually (libsndfile1-dev and imagemagick) 

./install.sh

Ok lets create some IQ files that will be used  to test the transmitter.

SSB Transmiiter

./pissb sampleaudio.wav ssbIQ.wav


A sample script testssb.sh is included.

FM modulation

pifm converts an audio file (Wav, 48KHz, 1 channel, pcm_s16le codec) to Narrow band FM (12.5khz excursion) and outputs it to a .ft file. Assuming your audio file is in your current working directory ./pifm sampleaudio.wav fm.ft

Connect a antenna to pin 4  long wire 40cm or longer depending on 1/4 lent of wavelength.

Pin Connection Diagram. Use coaxial cable to make connection

Here is a link with the filter details for the 2m Band

You could then transmit it on 100MHZ (please set a correct frequency to be legal) 

sudo ./rpitx -m RF -i fm.ft -f 100000 -l -c1


A sample script : testfm.sh is included.  add -c1 for pin 4 transmission in file

VFO
A VFO mode is provided to allows precise frequency resolution. For example to set a carrier on 100MHz (please set a correct frequency to be legal)sudo ./rpitx -m VFO -f 100000 -c1

Ok we got the Transmitter working Now lets get the rtl dongle working.
Follow my steps here http://zr6aic.blogspot.co.za/2013/02/setting-up-my-raspberry-pi-as-sdr-server.html

When you are complete with installation of rtl_sdr and have tested it wit rtl_test -t we can now check what audio devices the raspberry have.

sudo aplay -l
**** List of PLAYBACK Hardware Devices ****
card 0: ALSA [bcm2835 ALSA], device 0: bcm2835 ALSA [bcm2835 ALSA]
  Subdevices: 8/8
  Subdevice #0: subdevice #0
  Subdevice #1: subdevice #1
  Subdevice #2: subdevice #2
  Subdevice #3: subdevice #3
  Subdevice #4: subdevice #4
  Subdevice #5: subdevice #5
  Subdevice #6: subdevice #6
  Subdevice #7: subdevice #7
card 0: ALSA [bcm2835 ALSA], device 1: bcm2835 ALSA [bcm2835 IEC958/HDMI]
  Subdevices: 1/1
  Subdevice #0: subdevice #0

Now we need to install some audio utility programs to pyp and convert audio signals

sudo apt-get install sox libsox-fmt-all

ok lets test to see if we can receive 2m band transmission.

Tune the the rtl dongle for a frequency of 145.500Mhz and transmit a test signal.

sudo rtl_fm -f 145500000 -M fm 

Transmit a mp3 file recording

sox -t mp3 zr6aic_CQ_mono.mp3 -t wav -r 48000 -c 1 - | sudo ./pifm - 145.5 -c1

Installing ffmpeg


# build and install x264

git clone --depth 1 git://git.videolan.org/x264 cd x264 

./configure --host=arm-unknown-linux-gnueabi --enable-static --disable-opencl 

make -j 4

sudo make install

 # build and make ffmpeg
git clone --depth=1 git://source.ffmpeg.org/ffmpeg.git cd ffmpeg
./configure --arch=armel --target-os=linux --enable-gpl --enable-libx264 --enable-nonfree
make -j4
sudo make install


Install the following utility classes to help with the audio manipulation
sudo apt-get install libav-tools sox oggfwd libsndfile1-dev
sudo apt-get install fftw3 libfftw3-dev

Install csdr
git clone https://github.com/simonyiszk/csdr.git 

cd csdr 

git fetch 

git checkout dev 

make && sudo make install

Testing transmitter with Audio file (pin4 = -c1)

(while true; do cat speech48000.raw; done) | csdr convert_i16_f | csdr gain_ff 700 | csdr convert_f_samplerf 20833 | sudo rpitx -i- -m RF -f 145000 -c1

Putting the rpitx transmitter in TCP port listening mode (replace ip with Raspberry pi ip)

Sending audio from remote computer. (using mike from Linux computer)

arecord -fS16_LE -r48000 -c1 - | nc 192.168.10.128 8011

Testing RTL_fm (replace ip with your Raspberry ip)
sudo rtl_fm -M wbfm -f 98000000 | play -t raw -r 24k -es -b 16 -c 1 -V1 -
sudo rtl_fm -M wbfm -f 98000000 |nc  192.168.10.128 8011 -

Send rtl_dongle to transmitter (replace with your raspnerry ip)

sudo rtl_sdr -s 250000 -f 144300000 -p 0 - | nc -vv 192.168.10.128 8011

sudo rtl_sdr -s 4800 -f 144300000 -p 0 - | nc -vv 192.168.10.128 8011
 

Working RX with rtl dongle
sudo nc -l 8011 | csdr convert_i16_f | csdr gain_ff 8000 | csdr convert_f_samplerf 20833 | sudo rpitx -i- -m RF -f 145300 -c1

Working TX with pin 4

sudo rtl_fm -s48000 -g 49.6 -l 0 -M fm -f 434400000 |nc  192.168.10.128 8011 -

here is repeater without sqaulse

How to make the Repeater to auto start when the Raspberry start boot up.

Create a file and edit it

sudo vi /etc/init.d/Repeater

Add the following in the file and save it

#! /bin/sh
# /home/pi/sh/run_repeater.sh

### BEGIN INIT INFO
# Provides:          SDR repater start script
# Required-Start:    $remote_fs $syslog
# Required-Stop:     $remote_fs $syslog
# Default-Start:     2 3 4 5
# Default-Stop:      0 1 6
# Short-Description: Simple script to start a program at boot
# Description:       A simple script from www.stuffaboutcode.com which will start / stop a program a boot / shutdown.
### END INIT INFO

# If you want a command to always run, put it here

# Carry out specific functions when asked to by the system
case "$1" in
  start)
    echo "Starting SDR_repeater"
    # run application you want to start
    /home/pi/sh/run_repeater.sh
    ;;
  stop)
    echo "Stopping SDR_Repeater"
    # kill application you want to stop
    killall rtl_fm
    killall rpitx
    ;;
  *)
    echo "Usage: /etc/init.d/Repeater {start|stop}"
    exit 1
    ;;

esac

Make the file executable

sudo chmod 755 /etc/init.d/Repeater

Create a file in the /home/pi/sh/run_repeater.sh
Vi /home/pi/sh/run_repeater.sh

Add the Repeater script define above in this file so that it can auto start on boot time.

sudo rtl_fm -p 38 -s48000 -g 0 -l 3 -M fm -f 434400000 |csdr convert_i16_f | csdr gain_ff 12000 | csdr convert_f_samplerf 20330 | sudo rpitx -i- -m RF -f 145293 -c1&

Test the start and stop script.

Start the Repeater
sudo /etc/init.d/Repeater start

Stop The Repeater
sudo /etc/init.d/Repeater stop

Here is a video of the Test of the repeater ( I have changed the wires with a coaxial cable)

Video testing Fm demod and re mod cross band

What else can I do

Creating APRS transmitter
Setting up APRX rpitx with Raspberry Pi

aprs --callsign <callsign> --output - "<message>" | csdr convert_i16_f | csdr gain_ff 7000 | csdr convert_f_samplerf 20833 | sudo rpitx -m RF -i - -f 144800 -c1

Repeater configured in a single line 
sudo rtl_fm -p 38 -s48000 -g 0 -l 0 -M fm -f 434400000 |csdr convert_i16_f | csdr gain_ff 12000 | csdr convert_f_samplerf 20330 | sudo rpitx -i- -m RF -f 145293 -c1

Specifications (measured with New Low pass filter board )

Here is some results of Power measurements at 145Mhz. (@50ohm) 

• Voltage  1.3V
• Power 32.7 mW  (15.1dBm)

Total power consumption on power supply when repeater is running

Measured  5.44 V  and  540mA  = Total watts   2.937Watts

SDR Comparison

SDR Comparison

Name	Type	Frequency range	Band with	Channel	Host Interface	Windows	Linux	Mac	Estimated price
AirSpy	Pre-build	24-1750 MHz	20 MSPS MSps ADC sampling, up to 80 MSPS	1	USB	Yes	Yes	Yes using ports	US$199
SDRstick UDPSDR-HF1	Pre-built	0.1–30 MHz	80 Msps	1	1G Ethernet via BeMicroCV-A9	Yes	Yes	Yes	US$169
Apache Labs ANAN-10E	Pre-built	10 kHz – 55 MHz	122.88 Msps (14 bit ADC)	2	Gigabit Ethernet	Yes	Yes	Yes	US$995
Apache Labs ANAN-10/100	Pre-built	10 kHz – 55 MHz	122.88 Msps (16 bit ADC)	4	Gigabit Ethernet	Yes	Yes	Yes	US$1,649-US$2,449
Apache Labs ANAN-100D/200D	Pre-built	10 kHz – 55 MHz	122.88 Msps (16 bit ADC)	7	Gigabit Ethernet	Yes	Yes	Yes	US$3,299-US$3,999
SunSDR2	Pre-built	10 kHz – 160 MHz	160 MSPS	3/4	10/100 Ethernet, WLAN (embedded)	Yes	Yes	?	US$1,960
bladeRF	Pre-built	300 MHz - 3.8 GHz	80 kSPS - 40 MSPS RX/TX (12-bit ADC/DAC)	?	USB 3.0 SuperSpeed	Yes	Yes	Yes	US$420
FLEX-6700	Pre-built	0.01–73, 135-165 MHz	245.76 MSPS (transceiver)	8/8	Ethernet	Yes	Yes	Yes	US$7,499
FLEX-6700R	Pre-built	0.01–73, 135-165 MHz	245.76 MSPS (receiver)	8/8	Ethernet	Yes	Yes	Yes	US$6,399
FLEX-6500	Pre-built	0.01–73 MHz	245.76 MSPS (transceiver)	4/4	Ethernet	Yes	Yes	Yes	US$4,299
FLEX-6300	Pre-built	0.01–54 MHz	122.88 MSPS (transceiver)	2/2	Ethernet	Yes	Yes	Yes	US$2,499
FLEX-5000A	Pre-built	0.01–65 MHz	48, 96, 192 kHz (transceiver)	2/2	1394a Firewire	Yes	No	No	US$2,800
FLEX-3000	Pre-built	0.01–65 MHz	48, 96 kHz (transceiver)	1/1	1394a Firewire	Yes	No	No	US$1,700
FLEX-1500	Pre-built	0.01–54 MHz	48 kHz (transceiver)	1/1	USB	Yes	No	No	US$650
Perseus	Pre-built	10 kHz – 40 MHz (87.5–108 MHz using FM down-converter)	80 MSPS	?	USB	Yes	Yes	?	US$1,199
SDRplay: Radio Spectrum Processor	Pre-built	0.1–2,000 MHz	0.5-12 MS/s and up to 8 MHz bandwidth	0/1	USB	Yes	Yes	Yes	US$149
ISDB-T 2035/2037	Pre-built	50–960 MHz	0.5-12 MS/s and up to 8 MHz bandwidth	0/1	USB	Yes	Yes	Yes	US$25
Soft66AD / Soft66ADD / Soft66LC4 / Soft66RTL	Pre-built	0.5–70 MHz	External ADC required (I/Q output)	0/1	USB	Yes	Unofficially	?	US$20
FUNcube Dongle	Pre-built	64–1700 MHz	96 kHz	0/1	USB	Yes	Yes	Yes	US$160
FUNcube Dongle Pro+	Pre-built	0.15–240 MHz, 420-1900 MHz	192 kHz	0/1	USB	Yes	Yes	Yes	US$200
FiFi-SDR	Pre-built	200 kHz – 30 MHz	96 kHz (integrated soundcard)	0/1	USB	Yes	Yes	?	€120
SDR-IQ	PnP	0.1 kHz – 30 MHz	66.666 MHz	1/1 ?	USB	Yes	Yes	Yes	US$525
WinRadio WR-G31DCC	Pre-built	9 kHz – 50 MHz	100 MSPS	3/3	USB	Yes	No	No	US$950
USRP B200	Pre-built	70 MHz to 6 GHz	56 Msps	?	USB 3.0	Yes	Yes	Yes	US$675
USRP B210	Pre-built	70 MHz to 6 GHz	56 Msps	?	USB 3.0	Yes	Yes	Yes	US$1,100
USRP N200	Pre-built	DC to 6 GHz	25 Msps for 16-bit samples; 50 Msps for 8-bit samples	?	Gigabit Ethernet	Yes	Yes	Yes	US$1,515
USRP N210	Pre-built	DC to 6 GHz	25 Msps for 16-bit samples; 50 Msps for 8-bit samples	?	Gigabit Ethernet	Yes	Yes	Yes	US$1,717
USRP X300	Pre-built	DC to 6 GHz	200 Msps	?	Gigabit Ethernet, 10 Gigabit Ethernet, PCIe	Yes	Yes	Yes	US$3,900
USRP X310	Pre-built	DC to 6 GHz	200 Msps	?	Gigabit Ethernet, 10 Gigabit Ethernet, PCIe	Yes	Yes	Yes	US$4,800
Cross Country Wireless SDR receiver v. 3	Pre-built	472–479 kHz, 7.0–7.3 MHz/10.10–10.15 MHz, and 14.00–14.35 MHz	External ADC required (I/Q output)	1/1	Crystal controlled two channels	Yes	Yes	Yes	US$80
Realtek RTL2832U DVB-T tuner	Pre-built with custom driver	24–1766 MHz (R820T tuner) (sensitivity drops off considerably outside this range, but can go 0–2,200 MHz (E4000 tuner with direct sampling mod))	2.4 MHz (can go up to 3.2 MHz but drops samples)	?	USB	Yes	Yes	Yes	US$8 - US$10
SoftRock-40	Kit	7.5 MHz	48 kHz	1	USB	Yes	Yes	Yes	US$21
SoftRock RX Ensemble II	Kit	180 kHz – 3.0 MHz, and 1.8–30 MHz operation	External ADC required (I/Q output)	1	USB	Yes	Yes	Yes	US$67
ZS-1	Pre-built	300 kHz – 30 MHz	10 kHz, 20 kHz, 40 kHz, 100 kHz	3	USB 2.0	Yes	No	No	€1,399
HackRF One	Pre-built	1 MHz - 6 GHz	8 Msps - 20 Msps	1	USB 2.0	Yes	Yes	Yes	US$299
HiQSDR	prebuilt modules & kits, pcbs	30 kHz - 62 MHz	48 - 960 kHz	?	10/100 Ethernet	Yes	Yes	No	US$650 US$1,400
KiwiSDR	Pre-built	0.1 - 30Mhz	30Mhz	4	Beagle black	yes	yes	yes	USD 99
LimeSDR	Pre-built (full Open Source / Hardware)	100 kHz to 3.8 GHz	61.44 Msps (12 bit ADC)	?	USB 3.0, PCIe	Yes	Yes	Yes	US$299(USB) US$799(PCIe)

How to Decode DMR-MARK (mototurbo) with SDRsharp and rtl dongle on Windows 7

How to Decode DMR-MARK (mototurbo) with SDRSharp and RTL dongle on Windows 7

DSD decoding with SDRSharp and RTL dongle.

I found this website with very nice plugins for your SDR# software

http://rtl-sdr.ru/page/vse-dostupnye-na-etom-sajte-plaginy-s-kratkim-opisaniem (you can use this script to install all the plug-ins) http://rtl-sdr.ru/uploads/download/sdr-update.zip
Here is the list of plugins

1. Audio Processor Displays range of audio signal contains 6 adjustable bandpass filters and customizable deemfazis filter.
2. IF Processor Displays range IF signal to the demodulator, an asymmetric bandpass filter and a custom tracking notch filter.
3. Base band Recorder Writes the entire IQ stream received from the tuner to a file, you can choose a folder to store the recordings, and there is a scheduler for recording time. Large buffer for recording flow with high sampling rate without any losses. It can be controlled from other plug-ins.
4. IF Recorder Writes a stream of IQ intermediate frequency to a file, you can choose a folder to store the recordings, and there is a scheduler for recording time. It can be controlled from other plug-ins.
5. Audio Recorder Writes the audio file. Ample opportunities to control the format of the output file (mono, stereo, bit rate, sample rate). Extensive records management (do not write in the absence of a signal, create new files when changing frequency, etc.). Customizable file and folder names.
6. Decoder CTCSS squelch It displays the CTCSS tone in the presence of the signal and provides the squelch responds to set the tone.
7. DCS Decoder Squelch Displays DCS codes in the presence of a signal and contains a squelch responsive to certain code or the presence of any code in the signal.
8. AUX VFO Adds additional radio channels to SDR #. You can add more than one radio channel.
9. DSD Interface The plug consists of three parts. The first - an additional audio output from the demodulator can be used to output the audio signal through a virtual audio cable to other programs (WXtoImage, DSD, etc.). The second - a graphical interface to configure and run a digital signal decoder DSDPlus. And the third - to automatically turn off the sound output SDR # when choosing a frequency with a digital signal.
10. Time Shift It creates a memory buffer of up to several minutes. You can listen to the signals that have been broadcast and a present in the buffer. "All that is visible on the waterfall can be heard."
11. Digital Audio Processor It contains audio bandpass filter squelch by the presence of an audio signal and a signal scrambler inversion spectrum.
12. DDE Tracker + Scheduler Plug-in to communicate with the satellite tracking programs (Orbitron, WXTrack, SatPC32). When / companion care in the reception area is executed a list of commands for the satellite specified in the scheduler. It can control other plug-ins and run external programs.
13. QPSK Demodulator Plug-in for QPSK demodulation signal from the Russian satellite Meteor-M2 in real time. The final signal may be recorded in a file or transmitted via TCP on special version LRPTDecoder for decoding in real time. It may interact with other plug-ins.
14. TV The plugin displays the received PAL / SECAM TV signal. For receivers with a bandwidth of more than 7 MHz at the same time you can listen to the sound via the main radio SDR #. For rtl-sdr receivers need the modified file rtl-sdr.dll.
15. Frequency Manager Modified standard frequencies Manager SDR #. Added scanner iterates through the selected frequency. Added Manage window manager and some other improvements.
16. Frequency Scanner Fast scanner. It scans the specified frequency range. Saves frequency are not in the manager and activity time at these frequencies. It can scan multiple bands with different grid spacing, modulation bandwidth of the signal. There are modes of scanning all frequencies in the range, or only frequencies which are in the frequency or vice versa manager only frequencies that are not in the manager.
17. MPX Output It displays the selected audio device MPX signal after WFM demodulator with sample rate conversion to 192 kHz for further processing in other programs (eg RDSSpy).
18. Avia band 8.33 calculator Corrects manual input frequency range of air according to the standard steps for 8.33 kHz.
19. IQ Correction This is analogous to the standard functions of SDR # IQ correction. For slower computers help save some CPU time. There is a separate mode for R820T tuners - removal of only a constant component correction IQ on these tuners are required.
20. Audio Waterfall This plug-in created by Kiriyama. Adds SDR # waterfall displays the spectrum of the audio signal.21) Frequency LockThe function of this plugin is very simple, it blocks the frequency change settings in SDR #. Written at the request of the user to avoid accidental change of frequency of administration.

Here is a short description of the steps I took to install the SDRSharp plugins.

1. Firstly you need to install the SDRSharp software. Here is a link how to do that http://giga.co.za/smf/index.php/topic,34.0.html
2. Then Download the Plugin script from here. http://rtl-sdr.ru/uploads/download/sdr-update.zip
3. Unzip the sdr-update,zip file in the directory where you have installed the SDRSharp.exe in step 1.
4. Then unzip should create a directory sdr-update in the directory where the SDRsharp.exe file was unzipped.
5. There should be 3 files in the sdr-update directory. (httpget.exe,setup.bat and unzip.exe) (dir)
6. Make sure you have internet connection.
7. Then run the setup.bat file in the directory.
8. You will be asked some questions to override some installations and configurations, always say Y
9. Download and unzip DSDPlus application in any directory of your choice for from here http://www.dsdplus.com/download/dsdplus/DSDPlus1p074.zip mite have to change version number if there is a newer one available.
10. Create a start_dsdplus.bat file using Notepad  in the directory where you unzipped the DSDPlus1p074.zip zip file.
11. For now enter the following in the bat file with Notepad DSDPlus.EXE -i1 -o2 -fr
12. Set the playback device as follows making the VB-Cable the default device and Speaker just ready.
13.  Set the recording settings as follows. (Set VB-Cable as default and Stereo Mixer as ready)

SET VB-Cable as default and Stereo Mixer as ready.

14) In the Recording tab set the VB-Cable as default device and Stereo Mixer ready.

15) Set the sound levels as follows.

set cable volume not to high

16) Now run the start_dsdplus.bat file that you created in step 3 and check that the numbers correspond to the red in the pictures below.

17)  i = Audio input to DSDPlus and o = Audio Output from DSDPlus

18) Input to DSPPlus must be from VB-Cable and not any other device (Stereo mixer in my case).

19) Output must go to Speakers in my case to 2 

20)Your Audio input and output configuration should be different to the one I have.

21) You will then need to change it in the start_dsdplus.bat file and then re run start_dsdplus.bat file.

22) If your Audio Input and Output configuration is correct you will have to just set your audio levels coming from SDRSharp and going to speaker.

Your sound card numbers will be different and you need to update the bat file

24. Now we need to configure the DSD plugin in sdrSharp by giving it the path to your DSDPlus.

enter the path to your DSDPlus.exe in the DSD path block shown below. Now change the Audio settings in SDRSharp dsd plugin to be the same as as we did in the batch file by changing the audio device number.

Change input and output audio device as we did in batch file.

26) Now select the VB-Cable option in the SDRSharp DSD plugin menu to point to the VB-Cable

27) Then tune to DMR frequency channel  in your area with SDRsharp at the top frequency selection and start the DSD on the left menu.
I then got this warning pop box hidden behind my SDRSharp. Just click Run and the DSD popups will appear.

If all went right the following Scope,log and channel activity popups will appear.

Final check that the correct VB-Cable is used for Audio input and speaker as output.

28) For best results, make sure that all your SDR# and  VB-cable / VAC sample rates are set to 48kHz and that you have disabled “Filter Audio” in SDR#. Also, the audio volume of SDR# should not be set to high.
29)Here is a list of DMR frequencies in South Africa

30) Here is the list of repeater frequencies for DMR in South Africa http://zs6ro.org/index.php/dmr-repeaters/dmr-za-repeater-list. 
If all when ok you should be able to hear the decoded audio.

Hope this help.
Let me know if you get stuck by adding comments at the bottom..